Biomedical subjects

M Dimitrova

Publications and source records attributed to M Dimitrova.

At least 19 recordsLinked to original sources

PubMed2005

Slow and fast fatigable frog muscle fibres: electrophysiological and histochemical characteristics.

Continuous activity of isolated frog gastrocnemius muscle fibres provoked by repetitive stimulation of 5 Hz was used as an experimental model for fatigue development in different fibre types. Parameter changes of the elicited intracellular action potentials and mechanical twitches during the period of uninterrupted activity were used as criteria for fatigue evaluation. Slow fatigable muscle fibre (SMF) and fast fatigable muscle fibre (FMF) types were distinguished depending on the duration of their uninterrupted activity, which was significantly longer in SMFs than in FMFs. The normalized changes of action potential amplitude and duration were significantly smaller in FMFs than in SMFs. The average twitch force and velocity of contraction and relaxation were significantly higher in FMFs than in SMFs. Myosin ATPase (mATPase) and succinate dehydrogenase activity were studied by histochemical assessment in order to validate the fibre type classification based on their electrophysiological characteristics. Based on the relative mATPase reactivity, the fibres of the studied muscle were classified as one of five different types (1-2, 2, 2-3, 3 and tonic). Smaller sized fibres (tonic and type 3) expressed higher succinate dehydrogenase activity than larger sized fibres (type 1-2, 2), which is related to the fatigue resistance. The differences between fatigue development in SMFs and FMFs during continuous activity were associated with fibre-type specific mATPase and succinate dehydrogenase activity.

Animals↗

PubMed2004

Reactivity descriptors for the hydrogen bonding ability of pyridine bases.

The hydrogen bonding interaction between pyridine bases and water was theoretically studied by applying density functional theory computations at the B3LYP/631G(d,p) level. The theoretically determined binding energies for the complexation process correlate well with the experimental solvatochromic parameters beta for the respective bases. A very good linear relationship was also found between the evaluated binding energies of hydrogen bond formation and the respective electrostatic potential at nuclei (EPN) values at the pyridine nitrogen atom. It was found that the theoretical EPN values correlated linearly with the beta constants and the quantities could be employed as alternative. It was concluded that the electrostatic potential at nuclei characterized quantitatively the reactivity of the studied molecules toward the hydrogen bond formation. EPN values could be applied as hydrogen bond descriptors in QSAR studies.

Hydrogen Bonding↗

PubMed2004

New fluorescent method for the histochemical detection of dipeptidyl peptidase IV using glycyl-l-prolyl-2-anthraquinonyl hydrazide as substrate.

Glycyl-4-prolyl-2-anthraquinonylhydrazide (Gly-Pro-2-AH) was synthesized and used as a new fluorogenic substrate for the histochemical detection of dipeptidyl peptidase IV activity (DPP IV). The enzymatic hydrolysis liberates 2-anthraquinonyl hydrazine (2-AH). Further on, the primary reaction product reacts with an aromatic aldehyde to give an insoluble hydrazone. The final reaction product fluoresces orange-red when exited by green light (lambda(exc)=520-580 nm) and marks sites of enzymatic activity by an intensive fluorescence. This fluorescent method permits highly sensitive enzyme detection and causes only very low background tissue fluorescence. Thus enzyme locations in the capillary bed endothelium properly and sensitively stained, which has not been achieved by now. The new method is used successfully to demonstrate the enzyme in cryotome tissue sections from several rat organs.

Animals↗

PubMed2004

New fluorescent method for the histochemical detection of tripeptidyl peptidase I using glycyl-l-prolyl-l-met-2-anthraquinonyl hydrazide as substrate.

A new substrate for tripeptidyl peptidase I (TPP I; E.C.3.4.14.9)-Gly-L-Pro-L-Met-2-anthraquinonyl hydrazide (Gly-Pro-Met-2-AH) is synthesized and used for the fluorescent histochemical detection of the enzyme. The enzyme liberates low soluble 2-anthraquinonylhydrazine, which-couples quickly with 3-nitrobenzaldehyde (3-NBA) yielding a highly fluorescent water-insoluble hydrazone--3-nitrobenzylidene-2-anthraquinonylhydrazone. The latter compound is localized precisely at sites of enzymatic activity and marks them with a very bright and stable orange-red fluorescence after excitation with conventional monochromatic andlaser green light (lambda(exc)=520-580 nm). The new technique is used successfully for the visualization of the enzyme in tissue sections of different rat organs - and represent the first fluorescent histochemical method for that peptidase.

Aminopeptidases↗

PubMed2001

Increased redistribution of 99mTc-MIBI under the action of nitrate administration--a good tool for detection of myocardial vitality in patients with severe CAD.

BACKGROUND: The purpose of the study was to investigate and assess patients with severe, coronarographically documented coronary artery disease (CAD), previous myocardial infarction and left ventricular dysfunction, using radionuclide method for myocardial perfusion scintigraphy with 99mTc-MIBI and nitrate administration for detection of viable myocardium. MATERIAL AND METHODS: We investigated 56 patients (37 male, 19 female, mean age 58 +/- 8 years) with CAD and previous myocardial infarction, mean EF 38% +/- 12; divided into 2 groups: Group I--28 patients, investigated at rest, i.v. injected 370 MBq (99m)Tc-MIBI, scintigraphy performed at 30 min and 4th hour; Group II--28 patients, investigated at rest, i.v. injected 37 MBq (99m)Tc-MIBI, scintigraphy performed at 30 min, immediately after that administration of 20 mg Isosorbitdinitrate per os and delayed scintigraphy at 2nd and 4th hour. Myocardial SPECT imaging using Siemens Diacam with semiquantitative analysis of acquisition data was performed. RESULTS: The results established significant but low tracer redistribution in Gr. I, mean redistribution 17.5% +/- 5.6. After nitrate administration (Gr. II) we detected increased tracer redistribution, mean 30.4% +/- 7.8. The redistribution is higher at the 4th hour, compared to that obtained at 2nd hour after injection. Comparison of the results before and after PTCA showed sensitivity and specificity 93% and 67% respectively. CONCLUSION: It is concluded that after nitrate administration (99m)Tc-MIBI redistribution enhances noticeably and may play a feasible role in detection of viable myocardium in patients with severe CAD.

Journal Article↗

PubMed2000

Histochemical method for dipeptidyl aminopeptidase II with a new anthraquinonyl hydrazide substrate.

A new method for the histochemical visualization of lysosomal aminopeptidase dipeptidyl peptidase II activity (DPP II) is developed. The substrate L-Lys-L-Ala-5-chloro-1-anthraquinonylhydrazide-2HBr (Lys-Ala-CAH) is readily hydrolyzed by the enzyme to release 5-Cl-1-anthraquinonylhydrazine (CAH). The last compound is simultaneously coupled to an aromatic aldehyde, e.g. 4-nitrobenzaldehyde (p-NBA) or piperonal (3,4-methylenedioxybenzaldehyde; PPL), to form a highly insoluble deeply colored hydrazone, marking the enzyme locations. Using the new method, DPP II is successfully localyzed in tissue sections from different rat organs.

Animals↗

PubMed2000

Original method for the histochemical demonstration of tripeptidyl aminopeptidase I.

The original histochemical method for the visualization of tripeptidyl aminopeptidase I (TPP I, EC 3.4.14.9) is developed. The method is based on the new synthetic substrates Gly-L-Pro-L-Met(or L-Ala)-5-chloro-1-anthraquinonyl hydrazide (Gly-Pro-Met[Ala]-CAH). The final reaction product is represented as tripeptidyl-5-chloro-1 anthraquinonyl hydrazides (TPP-CAH). Upon the enzyme action the practically in aqueous media insoluble brown-reddish dye 5-chloro-1-anthraquinonyl hydrazine (CAH) is released, which reacts simultaneously with aromatic aldehydes as e.g. 4-anisaldehyde (p-AA) or 4-nitrobenzaldehyde (p-NBA), resulting in microcrystalline or amorphous deeply colored hydrazones. The last compounds mark accurately the locations of enzymatic activity. The biochemically suggested lysosomal localization of this collagen-degrading exopeptidase is thus confirmed on tissue sections. More information about the distribution of TPP I in different rat organs is presented as well.

Aminopeptidases↗

PubMed1999

New tetrazolium method for the histochemical localization of dipeptidyl peptidase IV.

New tetrazolium method for the histochemical localization of dipeptidyl peptidase IV (DPP IV), based on a newly synthesized substrate Gly-L-Pro-1-hydroxy-4-naphthylamide is proposed. Upon the enzyme hydrolysis of the substrate a strong reducing agent, i.e. 4-amino-1-naphthol is released, which reduces tetrazolium salts to water-insoluble, deeply colored formazans, that precipitate on the sites of enzyme activity, marking them accurately. No auxiliary electron acceptor is needed for the redox reaction. The incubation is performed at the optimal pH of the enzyme. Precise enzyme localization is achieved in all organs studied. Thus, the new method avoids most of the disadvantages of the methods in use and might open new possibilities in peptidases histochemistry.

Animals↗

PubMed1999

New tetrazolium method for the histochemical demonstration of gamma-glutamyl transpeptidase.

A new tetrazolium method for the histochemical demonstration of gamma-glutamyl transpeptidase is proposed. The method is based on a newly synthesized substrate-gamma-L-glutamic acid-1-hydroxy-4-naphthylamide, which upon the enzyme hydrolysis liberates 1,4-aminonaphthol--a powerful reducing agent that reduces tetrazolium salts quickly and quantitatively to deeply colored, water-insoluble formazans, precipitating on the sites of the enzyme activity and marking them accurately. The redox reaction is quick enough and does not need any auxiliary electron-acceptor. The method is very fast and convenient for the histochemical visualization of the enzyme.

Animals↗

PubMed1999

New method for the histochemical demonstration of dipeptidyl aminopeptidase I activity using a novel anthraquinoyl hydrazide substrate.

A new method for the histochemical localization of dipeptidyl aminopeptidase I (DPP I, cathepsin C), based on a newly synthesized substrate-Gly-L-Phe-5-chloro-1-anthraquinoyl hydrazide.HCl (Gly-Phe-CAH), is proposed. The enzyme activity liberates 5-chloro-1-anthraquinoyl hydrazine (CAH)--a water-insoluble brown-reddish compound, which precipitates on the enzyme locations. The primary reaction product reacts simultaneously or, otherwise, by post-coupling with p-anisaldehyde (p-AA), thus converting to the reddish-violet amorphous hydrazone--the final reaction product. The validity of enzyme localization is thus assured by the insolubility of the primary reaction product and does not depend on the rate of the second reaction step. The enzyme studied is successfully localized in different rat organs using the newly proposed technique.

Animals↗

PubMed1998

Incidence of dental caries /Is/ on milk molars /M1,M2/ in 3-8 year-old children from Plovdiv.

The incidence of dental caries /Is/ on deciduous molars in 1216 children aged 3 to 8 from Plovdiv has been studied. The results showed highest Is in the fissures of m1 and m2 and lowest Is on the smooth surfaces. The incidence of dental caries is getting higher with statistically significant differences in the lower jaw up to the 6th year and in the upper jaw up to 7th year of age. Is in the lower jaw is higher than that of the upper jaw only in the fissures.

Bulgaria↗

PubMed1998

Assessment of the behaviour of Bulgarian children dental patients at the age of 4-12.

The behaviour of Bulgarian children dental patients at the age of 4-12 has been studied by application of Venham's 6--grade behaviour scale. A sample of 274 clinically healthy children, divided in 3 age groups, were the object of the study. It has been found that the number of children whose behaviour has been assessed as one within the norm, is much greater that the number of the rest of patients-amounting to 77.74% and their number increasing with age. The negative behaviour, regardless of its rate, is not influenced by age.

Age Factors↗

PubMed1992

Effect of triiodothyronine on cAMP-dependent and cAMP-independent protein kinase activities in developing chick embryo liver.

1. Changes in liver cytosol cAMP-dependent kinase and cAMP-independent growth-related quercetin-inhibited casein kinase activities during chick embryo development were studied. 2. Both kinase activities were found to increase continuously during the experimental period. 3. Upon treatment of embryos with triiodothyronine, an activation of cAMP-dependent kinase A and cAMP-independent casein kinase was observed which was most pronounced on days 12 and 14.

Animals↗

PubMed1992

Microtubules and regulation of granulosa cell steroidogenesis by porcine granulosa cell conditioned medium.

Possible involvement of microtubules in the regulation of granulosa cell steroidogenesis by large follicle granulosa cell conditioned media (LGCCM) was assessed by monitoring the effect of agents that alter the cytoplasmic microtubule-tubulin equilibrium. The changes in microtubule organization and cell shape were examined by immunohistochemical procedure and morphometric analysis. Progesterone production stimulated by LGCCM was reduced by colchicine (agent that polymerizes microtubules) in a dose-dependent manner. In contrast, LGCCM stimulated progesterone secretion was significantly decreased by microtubule stabilizing agent (taxol: 1-10 microM). Cultured granulosa cells with a flattened appearance and projections after 24 h of incubation assumed a spherical configuration and were devoid of cytoplasmic processes when cultured with these agents. LGCCM stimulated GCs showed a reduction in the perimeter as compared with controls, although some cytoplasmic processes were observed. These findings suggest the involvement of microtubules in the regulation of cultured granulosa cell progesterone production by LGCCM, possibly through an effect on subcellular organelle distribution by altering the morphology of granulosa cells.

Animals↗

PubMed1988