PubMed Health⌕ Search

Biomedical subjects

L G Levin

Publications and source records attributed to L G Levin.

At least 19 recordsLinked to original sources
PubMed2003

[Complex approach to evaluation of natural quality of coloured juices].

A novel multidimensional approach to estimation of fruit and berry colored juice authenticity is proposed. It includes determination of quality (determination of 5-hydroxymethylfurfurol) and authenticity (determination of organic acids, hydrocarbons, anthocyanin pigments and artificial colorants) parameters. Both experimental and literature data on chemical composition of 12 colored fruits and berries are summarized. New composition characteristics of pomegranate, bilberry, red currant, blackberry and lingonberry are presented.

Anthocyanins↗
PubMed2000

Diagnosis of external root resorption using TACT (tuned-aperture computed tomography).

This study compared the ability of the TACT system of imaging and conventional D-speed film to detect simulated resorptive defects in cadaver teeth and jaws. Mandibular human jaw blocks were prepared and then split through the teeth in a mesial to distal direction so that the mandibular halves could be opened and reassembled when necessary. One half of each of 42 teeth was extracted, and areas on the tooth and corresponding bone identified to be studied. The jaws were opened and reassembled after no defects or after defects of different sizes (0.25, 0.5, 1.0, 2.0 mm) were placed in the tooth and the corresponding bone at predetermined evaluation areas. The teeth were imaged after each stage with conventional D-speed film using a standard paralleling technique, and with a modified orthopantomograph OP100 machine using a Schick #2 size CCD sensor as the image receptor. The source images were registered and TACT slices were generated using TACT Workbench Software. Three observers were asked to identify the presence of resorptive defects in the conventional film group and the TACT image group using specific criteria. TACT imaging was statistically superior to conventional radiographs in detecting defects that were present (Wilcoxon matched pairs signed ranks test P = 0.003). This was true for all sizes of defects examined. There was no difference between the two modalities when a defect was not present.

Cadaver↗
PubMed2000

Identification of root canals in molars by tuned-aperture computed tomography.

AIM: To compare the tuned-aperture computed tomography system of imaging to conventional D-speed film for their ability to identify root canals in extracted human molars. METHODOLOGY: Thirteen maxillary and six mandibular human molars were mounted in acrylic blocks to simulate clinical conditions by surrounding the teeth with a radiodense structure. The teeth were then imaged with conventional D-speed film using a standard paralleling technique, and with a modified orthopantomograph OP100 machine using a Schick no. 2 size CCD sensor as the image receptor. The source images were registered and TACT slices were generated using TACT Workbench Software. Three observers were asked to identify the number of canals in the conventional film group and the TACT image group using specific criteria. Ground truth was established by cross-sectioning the teeth at the coronal, middle, and apical thirds of the roots and directly visualizing the root canal morphology. RESULTS: TACT imaging detected 36% of 4th canals in maxillary molars and 80% of third canals in mandibular molars. Conventional film detected 0% of fourth canals in maxillary molars and 0% of third canals in mandibular molars. The differences in canal detection between the two techniques were statistically significant (Wilcoxon matched pair sign rank test, P = 0.001). CONCLUSIONS: In this study, the TACT system of digital imaging was superior to conventional film in the detection of root canals in human molars and may be useful for the detection of root canals that will probably be missed upon conventional X-ray examination.

Dental Pulp Cavity↗
PubMed1999

Expression of IL-8 by cells of the odontoblast layer in vitro.

Due to their peripheral location in the dental pulp and their cellular extension into dentin, odontoblasts are the first pulpal cells to encounter dental pathogens. The association of odontoblasts with immunoglobulins and dendritic cells during microbial invasion of dentin implies that these cells may possess a role in the innate and adaptive pulpal immune responses, however this has not been examined. A pivotal step in the innate immune response is the detection of foreign antigen and the recruitment of immune effector cells to the area. IL-8 is a potent chemotactic cytokine that plays an important role in the inflammatory response. The purpose of this study was to determine if odontoblasts are capable of expressing the pro-inflammatory chemokine IL-8. Human odontoblasts from intact, noncarious third molars were maintained in culture and exposed to Escherichia coli lipopolysaccharide (LPS) (serotype 055:B5) on day 4 for 8-10 h in a humidified 5% CO2 incubator. Control and experimental samples were assayed by reverse transcription-polymerase chain reaction (RT-PCR) and Western blot for the production of IL-8 mRNA and protein. Analysis of the PCR products revealed that cells of the odontoblast layer maintained in this culture model constitutively expressed low levels of IL-8, which were increased in response to E. coli LPS exposure. Western blotting confirmed that the mRNA was translated into protein. These results imply that odontoblasts are capable of producing of pro-inflammatory mediators, thereby actively participating in the recruitment of neutrophils in response to bacterial by-products.

Blotting, Western↗
PubMed1997

TNF-alpha release in monocytes after exposure to calcium hydroxide treated Escherichia coli LPS.

Lipopolysaccharide (LPS), a cell wall component of Gram negative anaerobic bacteria, has been implicated in the pathogenesis of periapical disease resulting from infected root canals. Calcium hydroxide [Ca(OH)2] has been shown to be an effective medicament in such infections, reducing the microbial titre within the canal. It has been proposed that the therapeutic effect of Ca(OH)2 may also be the result of direct inactivation of LPS. The aim of this study was to investigate whether the toxic potential of an Escherichia coli LPS could be reduced or eliminated by Ca(OH)2. Four concentrations of E. coli LPS ranging from 1-1000 ng/ml sterile water were incubated in duplicate either with 25 mg Ca(OH)2 or sterile water alone. Controls consisted of Ca(OH)2 without LPS or sterile water only. Monocytes were collected from peripheral blood by centrifuging through a gradient and plated to a specific density. Adherent monocytes were incubated for 4 days at 37 degrees C with 5% CO2 in M199 medium with 10% autologous serum. The different LPS solutions were added to the wells on day 5. After 4 h the supernatants were collected and quantitatively assayed for TNF-alpha using a commercial ELISA kit. Statistical analysis was performed with ANOVA. Results indicated that Ca(OH)2 is able to eliminate the ability of an E. coli LPS to stimulate TNF-alpha production in peripheral blood monocytes (P < 0.0001).

Calcium Hydroxide↗
PubMed1997

[Cranberries: chemical composition, nutritional and medicinal properties].

The contents of protein, fats, carbohydrates (glucose, fructose, sucrose, dietary cellulose), some vitamin (ascorbic acid, riboflavin, beta-carotene, vitamin E), polyphenolic compounds, organic acids, pectin, glycosides, macro- and microelements in red bilberry are presented. Antimicrobial effect and other effect of red bilberry and its use in traditional medicine and dietetics are also outlined.

Fruit↗
PubMed1997

[Content of toxic substances in breast milk after timely and premature labor].

Data on the contents of protein, fats and toxic compounds (PCB, DDT, gamma-Lindane) in breast milk Russian and Vietnamese women after timely and premature childbed are resulted. The contents of protein in transitive milk was higher than in mature milk, both timely childbed and premature one. The contents of protein in nature milk of the Vietnamese women was lower, than in mature milk of the Russian women (12 g/l against 16.5 g/l accordingly). The contents of fat in breast milk of the Russian women in lactation increased. Vietnamese women had very low fat level in mature milk (29 g/l against 42 g/l at the Russian women). The contents of toxic compounds (PCB, DDT, gamma-Lindane) in breast milk both, Vietnamese women and Russian women was rather high and significant frequency of detection of these compounds in milk was marked. The correlation contents of basic food components in breast milk and level of toxic compounds was absent.

DDT↗
PubMed1996

Induction of human factor VIII inhibitors in rats by immunization with human recombinant factor VIII: a small animal model for humans with high responder inhibitor phenotype.

Hemophilia A is a clotting disorder that is due to reduced or absent coagulation factor VIII (FVIII) activity. In approximately 25% of people with severe hemophilia A, standard treatment with intravenous plasma-derived or recombinant FVIII (rFVIII) induces anti-FVIII antibodies that inhibit FVIII activity (inhibitors). We describe the development of a rat model to study the formation of inhibitors. Immunization of rats with human rFVIII in adjuvant induced an anti-human rFVIII antibody response characteristic of an anti-FVIII inhibitor response in hemophilia A patients. The rats exhibited a rapid, polyclonal secondary antibody response to human rFVIII. These antibodies were reactive against epitopes located in the heavy and light chains. All the rFVIII-immunized rats developed antibodies against the FVIII C2 domain, a region of major reactivity in hemophilia A patients with inhibitors. Furthermore, competition ELISAs demonstrated that rat and human anti-FVIII antibodies recognized identical or overlapping epitopes of the FVIII molecule. The rat anti-FVIII antibodies also functioned as human FVIII inhibitors with titers ranging from 120 to 2048 Bethesda Units (B.U.). We propose that this rat model may be useful to investigate immune responses to FVIII and may lead to better therapies for FVIII inhibitors.

Animals↗
PubMed1996

Induction of human factor VIII inhibitors in rats 2: Fine mapping of rat anti-human rFVIII antibodies.

Inhibiting antibodies in patients with hemophilia A pose a significant therapeutic dilemma in the treatment of bleeding episodes. The genetic factors which predispose hemophiliacs to inhibitors and the optimal method for inhibitor suppression remain obscure. Hence, an animal model of the human FVIII inhibitor response is of potential value. Sprague-Dawley rats immunized with human recombinant FVIII (rFVIII) subsequently developed abnormal coagulation parameters coincident with the development of an immune response to the human protein. The epitopes for the resultant rat anti-rFVIII antibodies were mapped using a random fragment expression library constructed from the FVIII cDNA. Antigenic regions located within the A1, First and Second Acidic and B domains were mapped. Rat immunoglobulins reactive with the individual epitopes were immunoaffinity purified and assayed for inhibitory activity. Several of the epitopes mapped using the rat antibodies were similar to regions previously shown to be antigenic for human inhibitors. By contrast, no epitopes were mapped to the A2 domain with the techniques used. This may be due to the possible presence of conformational epitopes in this area which cannot undergo fragmentation and still retain antigenicity or the presence of relatively low concentrations of antibodies to this region. The rat model shares some similarity with both the auto- and alloimmune human response to FVIII and therefore may be a valuable model for studies on the induction and suppression of the inhibitor response.

Animals↗
PubMed1988

Osteoblasts increase their rate of division and align in response to cyclic, mechanical tension in vitro.

Bone adapts to physical deformation in vivo, yet the mechanism of the adaptive process remains unknown. One reason for this perplexity has been the difficulty in examining the effects of a well-defined deformation regimen on individual bone cells. With the utilization of novel, flexible-bottomed cell culture plates, one can study the effects of cyclic strain on the morphologic and biochemical adaptations of individual osteoblasts in vitro. Avian, calvarial osteoblast-like cells, from passes 2-5, responded to cyclic strain, by increasing their rates of DNA synthesis and cell division during the first 72 h after initiation of a continuous deformation regimen comprised of 3 cycles per min of 0-24% elongation. In addition, within hours after initiation of the deformation regimen, cells oriented 90 degrees to the applied strain field at the periphery of the culture plate in the region of maximum strain and elongation.

Animals↗
PubMed1987

Mechanical stress stimulates aortic endothelial cells to proliferate.

The effects of applied cyclic tensional deformation and relaxation on cultured bovine aortic endothelial cells were examined. Endothelial cells from passages 3 to 9 were seeded in flexible-bottomed plates and allowed to attach for 24 hours. Endothelial cells in the experimental group (n = 6 wells per time point) were placed in a vacuum-operated stress-providing instrument that exerted an average elongation of 10% at maximum downward deflection of the culture plate bottom. The stretched endothelial cells were subjected to repeating cycles of 10 seconds elongation and 10 seconds relaxation from days 1 through 7 in culture. Endothelial cells in the control group (n = 6 wells per time point) were subjected to similar incubation conditions as the experimental group but without tensional deformation. Tritiated thymidine was added to cells 24 hours before harvesting. On days 0, 1, 3, 5, and 7 cells were counted and analyzed for trichloroacetic acid-precipitable tritiated thymidine incorporation. The results showed that 3 cycles/min mechanical stretching stimulated deoxyribonucleic acid synthesis and endothelial cell division. We conclude that cyclic tensional deformation may stimulate endothelial cell proliferation. It is possible that naturally occurring cyclic mechanical deformation in vivo, such as the repetitive stretching and relaxation of aortic tissue by the heart, may invoke a particular pattern of synthesis and division in endothelial cells.

Animals↗
PubMed1976

[A method of studying hydrochloric acid secretion in isolated gastric mucous membrane using a two-channel pH-meter].

A new method of hydrochloric acid secretion recording on two symmetrical parts of the same isolated gastric mucosa is described. A two-channel system which had a number of important advantages over a single-channel system was used. The advantage of this method lay in a possibility of a more exact differentiation of the influence of different substances on the rate of H+ secretion and in a considerable decrease in the number of animals required for the experiments. The apparatus scheme for a two-channel recording of H+ secretion, and design of the four-chamber cuvette are described.

Gastric Acidity Determination↗
PubMedDate not supplied

[Effect of alimentary alpha-tocopherol deficiency on the fatty acid composition of phospholipids in the subcellular membranes of the liver cells and high density lipoproteins in the blood plasma].

In experiments on rats a positive correlation was demonstrated between the changes in the fatty-acid composition of hepatocytic intracellular membrane phospholipids and blood plasma high density lipoproteins. The data obtained evidence the existence in the blood of several mechanisms of alpha-tocopherol deficiency action on hepatocytic phospholipids and blood plasma protein-lipid complexes.

Animals↗