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Biomedical subjects

A Popov

Publications and source records attributed to A Popov.

At least 37 records · Page 2Linked to original sources
PubMed1997

The effect of chronic alcohol use on the heart before and after transplantation in an experimental model in the rat.

BACKGROUND: Alcohol has potential deleterious effects on donor heart function. This study was conducted in rats to determine whether long-term alcohol ingestion produces impaired hemodynamic performance while maintaining a normal left ventricular ejection fraction in donor hearts before transplantation and whether donor cardiac function is affected after heart transplantation. METHODS: Rats fed 30% alcohol in their drinking water for 12 weeks were compared with rats fed a normal diet. Left ventricular ejection fraction was measured by echocardiography with Simpson and single plane Dodge formulas in living sedated rats after 10 and 12 weeks of alcohol feeding. Explanted heart function was assessed before and 3 days after heterotopic heart transplantation (no immunosuppression) with a Langendorff preparation. RESULTS: Blood ethanol levels at 4 and 8 weeks were 0.08 +/- 0.04 and 0.08 +/- 0.09 gm/dl. Left ventricular ejection fraction was similar in the group fed an alcohol diet for 12 weeks when compared with the control group (65.4% +/- 1.6% vs. 66.5% +/- 2.9%, p = 0.33). Explanted alcohol-fed hearts before transplantation had significantly lower maximum and developed pressures and had a blunted response to 0.1 ml 10(-9) mol/L isoproterenol. After transplantation alcohol-fed hearts had significantly lower maximum and developed pressures and decreased maximum rates of pressure rise and pressure decline. Allografts (ACI to Lewis) exhibited decreased function in comparison with isografts (ACI to ACI). CONCLUSIONS: Alcohol feeding for 12 weeks in rats does not affect pretransplantation left ventricular ejection fraction, but it impairs explanted heart function, both before and after transplantation, resulting in a subclinical cardiomyopathy that is worsened by the presence of allograft rejection. Long-term alcohol exposure and rejection have independent, additive detrimental effects on left ventricular performance of the transplanted heart. Alcohol-exposed hearts may not be suitable donors.

Animals↗
PubMed1996

Development of the mesencephalic and diencephalic catecholamine systems in human fetuses: uptake and release of catecholamines in vitro.

Development of catecholamine (CA) systems of the ventral mesencephalon and diencephalon were studied in human fetuses at age 6, 8, 10 and 12 weeks, evaluating the CA specific uptake and K(+)-stimulated release with the isotopic biochemical technique. In the mesencephalon, the [3H]dopamine (DA) uptake was detected as early as 6 weeks, suggesting the existence of either CA neurons or fibers. This was followed by gradual increase of the [3H]DA uptake up to 10 weeks and a subsequent fall at 12 weeks. In the diencephalon, the uptake was first observed at 8 weeks, followed by its decrease at 10 weeks and subsequent increase at 12 weeks. The dynamic uptake is considered as a manifestation of the continuous differentiation of CA neurons and sprouting of CA fibers. In contrast to uptake, no CA release was detected in response to membrane depolarization in the diencephalon and mesencephalon at any age studied, suggesting a timing dissociation between the onset of the CA uptake and K(+)-provoked release in the course of neuron differentiation in human fetuses.

Brain↗
PubMed1996

Electron microscopic investigation on Ito cells and Disse's space in patients with extrahepatic cholestasis. Immunohistochemistry of collagen type IV and fibronectin in hepatic sinusoids.

Extrahepatic cholestasis is one of the main factors causing liver fibrosis. Surgical biopsies of six patents were studied: one with normal liver (control patient), and five with different degrees of extrahepatal cholestasis with hepatocellular degenerative and necrotic changes. Monospecific antibodies directed against type IV collagen and fibronectin were localized by light microscopical immunohistochemistry. Type IV collagen was found in all basement membranes: ductal, vascular, neural, Intensive, almost continuous deposits of it were found along the entire length of the sinusoid. Fibronectin, the structural glycoprotein, was codistributed with type IV collagen in portal matrix and in perisinusoidal location. It did not decorate the basement membranes of bile ducts and stained more intensely than type IV collagen at the border between portal stroma and parenchyma. The intensity of the two antibodies increased corresponding with the heaviness of parenchymal deterioration. There was weaker staining behavior of the extracellular matrix regarding collagen IV and fibronectin in the area of heavy bilirubin impregnation. The sinusoid morphology in the regions with fibrosis and increased extracellular matrix formation in periportal areas was reported. Disses's space was distended and occupied by collagen bundles, amorphous matrix, swollen hepatocyte microvilli, and basement membrane-like material. Ito cells transformed into transitional cells or myofibroblast-like cells. Sinusoidal changes and increased collagen IV as well as perisinusoidal fibronectin formation coincided with the aggravation of cholestasis.

Biopsy↗
PubMed1995

Sinusoidal changes in extratumoral liver tissue. Report of a case of metastatic liver small cell carcinoma with collagen IV detection and ultrastructural studies.

Biopsy sections taken from liver tissue near and far away from metastases were investigated histologically, histochemically, electronmicroscopically and immunohistochemically in order to establish collagenization and extracellular matrix (ECM) formation in the space of Disse. Extratumoral tissue far away from metastases showed perisinusoidal fibrosis (van Gieson positive), moderate immunoreaction with anticollagen IV antibody, and expressed collagen formation in the space of Disse. Liver tissue near metastases showed strongly expressed paratumoral fibrosis and moderate perisinusoidal fibrosis, dilatation of Disse space with discontinuous basement membrane (BM) formation, and a lot of collagen bundles. Ito cells acquired features of transitional cells (TSC) or myofibroblast (MF)-like cells. Based on these results it is concluded that there were sinusoidal changes in extratumoral tissue, probably provoked by some cytokines released from tumoral cells.

Biopsy↗
PubMed1995

[The effect of an extract of sea buckthorn (Hippophae rhamnoides L.) on the healing of experimental skin wounds in rats].

The effect exerted by Hippophaë rhamnoides L. extract on the healing of experimental wounds in rats is studied histomorphologically in dynamics. The animals are divided up in three groups, as follows: group one--controls, group two--controls treated with indifferent carrier (carbopol gel), and group three--experimental, treated with carbopol gel containing extract of Hippophaë rhamnoides L. The wounds induced are standard, oval to elliptic with diameter about 3 cm. In groups I and II they are subjected to daily daubing over a 10-day period. The study of cytologic smears at 8, 24 and 48 hours, and biopsy performed on the 10th day show that in group three the epithelization is more intensive and occurs earlier, and granulation tissue differentiation (mature collagen fibers, profuse vascularity) is quicker, by comparison with groups one and two. The markedly expressed stimulating effect on the healing process is explained with the rich content of vitamins (A, C, E etc.) and microelements (sulfur, selenium, zinc, copper etc.) in the extract used.

Acrylic Resins↗
PubMed1994

FUNCTION OF THE TENSOR MUSCLE IN THE CICADA TIBICEN LINNEI

The calling song and the disturbance squawk of the cicada Tibicen linnei (Insecta: Homoptera) are described in terms of their physical parameters. The calling song is composed of quiet parts, which are very similar to the disturbance squawk, and loud parts, which are amplitude- and rate-modulated. The role of the tensor muscle acting on the tymbal frame in modulating the sound pulse amplitude was investigated. We demonstrate by tensor nerve recordings, by mechanical mimicking of the tensor muscle action and by electrical stimulation of the tensor nerve, that the contraction of the tensor muscle is responsible for (a) initiating sound production and (b) modulating the sound pulse amplitude. These results allow us to construct a model which suggests that the tensor shifts the tymbal into a mechanical working range that enables sound production and modulation of the sound pulse amplitude.

Journal Article↗
PubMed1994

AUDITORY THRESHOLD CHANGE IN SINGING CICADAS

The hearing sensitivity in singing cicadas is reduced during sound production by a folding of the tympanal membranes. Using electrophysiological recording and nerve stimulation techniques, we have shown an effect of the folded tympanum on the auditory threshold of two species of cicadas, Tibicen linnei and Okanagana rimosa. Auditory thresholds of both species increased by about 20 dB when the tympana folded during singing. In T. linnei the increase in threshold affected the whole frequency range, from 1 to 16 kHz, in a similar way. Electrical stimulation of one or both auditory nerves resulted in a folding of both tympanal membranes in a way very similar to that seen in singing animals. We have demonstrated that a cicada male is able to adjust its auditory threshold within a range of about 20 dB by the tympanal folding mechanism.

Journal Article↗
PubMed1994

Islet amyloid polypeptide in Psammomys obesus: lack of correlation between insulin resistance and plasma IAPP levels.

Sand rats (Psammomys obesus) develop insulin resistance and diabetes when given a standard laboratory diet. We have examined the presence of islet amyloid polypeptide (IAPP), or amylin, in these animals. IAPP is present in the beta-cells of pancreatic islets, its localization and intensity of immuno-reactivity are, thus, similar to that of insulin. In insulin resistant Psammomys obesus, insulin and IAPP immuno-reactivity in pancreas are markedly decreased, plasma insulin levels are 20-fold higher than in controls but IAPP levels are not different from those of normal animals. Therefore, insulin resistance in Psammomys obesus does not appear to result from an elevated plasma IAPP level nor from development of amyloid deposits.

Amyloid↗
PubMed1994

Immunohistochemical study on pigmented nevi (preliminary communication).

The human ABH blood-group antigen expression of cytokeratin, S-100 protein, and the melanoma-associated antigen was studied in 12 cases of pigmented nevi. The biotin-streptavidin immunostaining system was applied. ABH antigens were found both in the endothelial cells and in the germinative epidermal layer. The flat overlaying epithelium, single melanocytes and melanoblasts were positive for cytokeratin. Some basilar cells and the giant multinucleate cells in the Spitz nevi stained for S-100 protein. The melanoma-associated antigen was visualized in the upper epidermal layers as well as in some melanocytes. The present article discusses the specificity of the antigens studied as well as some immunologic traits of potential malignant development of Spitz nevi.

Antigens, Neoplasm↗
PubMed1993

[The immunobiological functions of human ABO (H)-system blood-group antigens].

The human ABO (H) blood group antigens are genetically determined carbohydrate structures found in different cells and tissues. The modulation in their expression in the course of human onto- and oncogenesis gives grounds for speculations concerning the role of ABO (H) antigens as molecules, participating in cell interactions, adhesion and inhibition events, as well as in tumor metastases. The deletion of antigenic determinants observed in a number of human carcinomas, and the epitope homology between the blood group antigens and the carcinoembryonic antigen, focuses on clarifying the diagnostic and prognostic value of the ABO (H) antigens as tumor-associated markers.

ABO Blood-Group System↗
PubMed1993

[Morphological and morphometric studies of the pancreas in type-2 diabetes mellitus].

The authors investigated histologically and immunohistochemically 60 cases with diabetes mellitus type 2. By means of the morphometric method of Weibel et al. (1969) they established diminished volume density of the insular tissue in total pancreas. The morphologic and morphometric data revealed evidence that diabetes mellitus most probably presented a heterogeneous group of pancreatic lesions manifested by disturbances of carbohydrate homeostasis.

Diabetes Mellitus, Type 2↗
PubMed1993

[A pharmacological study of the hepatoprotective activity of fructose-1,6-diphosphate].

A fructose-1,6-diphosphate preparation was tested for hepatoprotective activity through biochemical and morphologic studies in experiments on Wistar rats sustaining D-galactosamine- and paracetamole-induced hepatotoxicity. Findings indicated the modeled hepatic lesions to be readily reproducible, to simulate some characteristics of human liver pathology, and to be suitable for testing substances expected to have hepatoprotective action; intraperitoneal administration of fructose-1,6-diphosphate at a dose of 1000 mg/kg body weight proved moderately protective against liver damage by D-galactosamine; the benefit observed concerned mostly dystrophic and inflammatory changes in the liver; in a number of cases, correlation was noted between biochemical serum parameters and pathomorphologic liver alterations.

Acetaminophen↗
PubMed1993

Expression of A, B and H blood-group antigens and carcinoembryonic antigen in human tumours.

The parallel expression of ABH blood-group antigens and of the carcinoembryonic antigen was examined applying the biotin-streptavidin immunostaining system. Monoclonal antibodies to the ABH antigens newly produced by us and a polyclonal antibody to the carcinoembryonic antigen (Ortho) were used as primary antibodies. Human tumours derived from six different organs were studied. ABH antigens showed a heterogeneous expression. They were entirely missing in some neoplastic tissues and found in single or in clustered tumour cells in others. The staining for the carcinoembryonic antigen revealed stronger intensity and covered large malignant areas. The possible functions of ABH blood-group antigens as tumour-associated structures are discussed. A number of tumour-associated antigens have been identified which may serve to improve the early diagnostics of tumour processes in man. Recently, the blood-group antigens (BGA) from the ABO/H system have attracted the attention of many investigators who regard them as differentiation antigens and as tumour-associated structures. Oncogenesis is accompanied by a block in BGA biosynthesis as a result of an altered ontogenetical programme. This process leads to: a) deletion of BGA-structures in malignant cells; b) neoantigen expression (onco-developmental markers) and c) appearance of BGA-incompatible antigens. The aim of the present investigation is to examine the coexpression of A, B and H BGA and of the carcinoembryonic antigen (CEA) in malignant human tissues. Using the monoclonal antibodies (MAbs) to ABH-BGA newly produced in our laboratory, some insufficiently explored organs like the mammary gland and especially its metastases were also tested.

ABO Blood-Group System↗