Search PubMed⌕ Search

Biomedical subjects

J Carlsson

Publications and source records attributed to J Carlsson.

At least 235 records · Page 13Linked to original sources
PubMed1989

Microbial aspects of frequent intake of products with high sugar concentrations.

The Vipeholm Study showed that a frequent intake of products with high sugar concentrations increases caries activity. This effect of sugar was explained by the acid production of bacteria on the teeth. In the following 40 yr many microbial characteristics have been described, which are important in the pathogenesis of dental caries. This contribution focuses on one characteristic of the cariogenic bacteria; their acidurance. Compared to other oral bacteria the cariogenic lactobacilli and mutans streptococci have enzymes with greater resistance to acid, and greater capacities of the cells to extrude protons from the cytoplasm. The most important enzyme for the extrusion of protons is a membrane-bound proton-translocating ATPase. This enzyme is found in higher amounts and is working at lower pH in the cariogenic bacteria. Another important characteristic of the cariogenic bacteria is their production of lactic acid when they are exposed to high concentrations of sugar. Lactic acid has a pK of 3.8, while other carboxylic acids have a pK of 4.8. The bacterial cell membrane is permeable to undissociated carboxylic acids. These undissociated acids act as carriers to bring protons back into the cytoplasm. Bacteria with lactic acid as fermentation product have therefore the possibility to grow and produce acids at one pH unit lower than bacteria with, for example, acetic, propionic, or butyric acid as fermentation product.

Bacteria↗
PubMed1989

Selenite-induced variation in glutathione peroxidase activity of three mammalian cell lines: no effect on radiation-induced cell killing or DNA strand breakage.

The selenium-dependent glutathione peroxidase activities of three mammalian cell lines, HT29, P31, and N-18, cultured in medium with low serum content, increased about 2-, 5-, and 40-fold, respectively, after supplementation with 100 nM selenite. Catalase, CuZn superoxide dismutase, and Mn superoxide dismutase activities were not generally influenced by selenite supplementation, and there was only a minor nonselenium-dependent glutathione peroxidase activity in the investigated cell lines. Gamma-irradiated control and selenite-supplemented cells showed no changes in the surviving fractions, as estimated by clonogenic survival or [3H]-thymidine uptake, nor were there any significant differences between the two groups in the induction of DNA strand breaks after gamma irradiation under repairing (37 degrees C) or nonrepairing (0 degrees C) conditions. The results suggest that selenium-dependent glutathione peroxidase does not contribute significantly to the radiation resistance of cultured mammalian cells.

Animals↗
PubMed1988

Relations between pH, oxygen partial pressure and growth in cultured cell spheroids.

The pH gradients, oxygen partial-pressure gradients and growth curves were measured for 7 different types of spheroids. Growth curves were measured in liquid overlay culture and thereafter the spheroids were attached to cover glasses and transferred to a chamber for micro-electrode measurements. The spheroids were randomly divided for pH or pO2 measurements which then were made under conditions as identical as possible. The decreases in pO2 and pH, delta pO2 and delta pH were calculated as the difference between the values in the culture medium and the values 200 micron inside the spheroids. Each type of spheroid had a certain relation between delta pO2 and delta pH. The human colon carcinoma HT29, the mouse mammary carcinoma EMT6 and the hamster lung V79-379A spheroids had high values of the quotient delta pO2/delta pH. The human thyroid carcinoma HTh7 spheroids and the 3 types of human glioma spheroids had lower quotients. There was a tendency for fast-growing spheroids to have high quotients. Two extreme types of spheroids, HT29 (high quotient) and U-118 MG (low quotient) were analyzed for lactate production and oxygen consumption. The U-118 MG spheroids produced about 3 times more lactate and consumed about 3 times less oxygen than the HT29 spheroids. The differences in lactate production could not be explained by differences in the pyruvate Km values of lactate dehydrogenase. The results indicate that there are significant metabolic differences between the spheroid systems studied.

Animals↗
PubMed1988

Penetration of substances into tumour tissue. Model studies using saccharides, thymidine and thymidine-5'-triphosphate in cellular spheroids.

In order to achieve a better understanding of factors involved in drug penetration into poorly vascularized tumour tissue, the penetration of some model substances was studied in vitro. Multicellular human tumour spheroids were used as model system. The test substances were [3H]thymidine and [14C]glucose, both of which are capable of passing easily through cell membranes, and [3H]thymidine-5'-triphosphate, [3H]sucrose and [3H]inulin, all of which are unable to pass directly through cell membranes. The penetration of these substances was studied using a dry histological and autoradiographical method preserving the distribution of water-soluble substances. The two thymidine compounds penetrated very efficiently into the spheroids, and their penetration patterns were rather similar. The saccharides differed somewhat in their penetration properties. Glucose had the fastest penetration and inulin the slowest. After 15 min, however, inulin was also found isotropically distributed within the spheroids. Thus, extracellular penetration seemed to be a possible way for a substance to reach the central parts of a spheroid. The differences between the saccharides could be due to some extent to differences in molecular weight and solubility.

Carbohydrate Metabolism↗
PubMed1988

Catalase inhibition by sulfide and hydrogen peroxide-induced mutagenicity in Salmonella typhimurium strain TA102.

The lethal and mutagenic effects of hydrogen peroxide were studied in exponentially growing cultures of Salmonella typhimurium strain TA102. Exposure of the cultures to non-lethal levels of sodium sulfide significantly increased the lethality and mutagenicity of hydrogen peroxide. The catalase activity was decreased in cells exposed to sodium sulfide, but there were no changes in the cellular levels of superoxide dismutase, glutathione reductase, or NADPH-dependent alkyl hydroperoxide reductase. Hydrogen peroxide-induced mutagenesis and killing of S. typhimurium strain TA102 in the presence of sulfide may in part be explained by an inactivation of catalase by sulfide.

Catalase↗
PubMed1988

Monoclonal antibodies to a synthetic peptide corresponding to a repeated sequence in the Plasmodium falciparum antigen Pf155.

Mouse monoclonal antibodies were prepared against a synthetic peptide (EENVEHDA) corresponding to a tandemly repeated sequence in the C-terminus of the Plasmodium falciparum antigen Pf155. One antibody (IgG1) producing hybridoma was studied in detail. The specificity of the antibody was determined by enzyme-linked immunosorbent assays using bovine serum albumin-conjugated or free peptides as solid phase antigens and various synthetic peptides for inhibition. The antibody reacted with Pf155 as detected by immunofluorescence and immunoblotting. It was also an efficient inhibitor of merozoite invasion in P. falciparum in vitro cultures indicating that it defines a biologically important epitope present on the native Pf155 molecule.

Animals↗
PubMed1988

Extracellular matrices in multicellular spheroids of human glioma origin: increased incorporation of proteoglycans and fibronectin as compared to monolayer cultures.

Tumor spheroids were cultured from five human glioma cell lines which differed considerably in their relative amount and composition of glycosaminoglycans (GAG), fibronectin and other extracellular matrix (ECM) components when grown as monolayer cultures. These differences were also evident when the cells were grown as spheroids. Under the 3-dimensional geometry of the spheroid system, there was, however, generally a more extensive ECM. Especially noteworthy was the presence of a small proteoglycan, probably a dermatan sulphate proteoglycan, in the ECM of the spheroids, but not in the monolayers. Noteworthy was also the appearance of fibronectin in spheroids which did not show any staining for fibronectin when grown as monolayer. The two spheroid types (U-87MG, U-105MG) with the most extensive matrix, and with the lowest proportion of hyaluronic acid (HA), had a low proliferation rate, whereas the three other spheroid types (U-118MG, U-138MG, U-251MG) with a less extensive ECM, and a relatively high production of HA had a much higher proliferation rate. These data provide further evidence for the usefulness of culturing cell lines as spheroids in the process of understanding important cell biological phenomena.

Cell Adhesion↗
PubMed1987

Characterization of monoclonal anti-DNA antibodies and visualization of binding to chromosomes and cell nuclei.

Monoclonal antibodies against DNA from two hybridoma cell lines were produced and characterized. One had specificity for single stranded (ss) DNA with some cross-reactivity to RNA, while the other was specific for both single (ss) and double stranded (ds) DNA. The latter ds and ss DNA-binding antibody was used as a model for analysing the distribution of the epitope in chromosomes and cell nuclei. A linear correlation between antibody binding and propidium iodide counterstaining was found on flow cytometric analysis of suspended chromosomes. Immunofluorescence of rat myoblast cells showed a speckled distribution of the antibody in the nucleus with a variability between the cells. Using electron microscopy to visualize antibody binding with gold particles, codistribution with uranyl acetate staining of leucocytes was found. These results suggested that the antibody preferentially binds to condensed chromatin in cells and chromosomes.

Animals↗
PubMed1987

Variations among cultured cells in glutathione peroxidase activity in response to selenite supplementation.

The aim of this study was to devise conditions for manipulation of the activity of selenium-dependent glutathione peroxidase in cell lines by means of variation in culture medium contents of selenite and fetal calf serum. Nine different cell lines were studied. A low glutathione peroxidase activity was, in most cases, obtained by the use of a medium with a low (2%) serum content. Selenite induced in most of the cell lines an increase in glutathione peroxidase activity, with a plateau ranging from 10 nM to 300-1000 nM. Growth-retarding effects of selenite became apparent at 300-2000 nM, showing a large cell line variation. Supplementation with 50-100 nM selenite for 1 week should generally be suitable for maximal glutathione peroxidase induction. The selenium contents of serum batches were highly variable, pointing to the importance of using only one well-defined, preferably low-selenium, batch. The glutathione peroxidase activities varied considerably between cell lines and the selenite-induced increases ranged from negligible to more than 10-fold. The availability of cell lines with such variable responses should be valuable for experiments aimed at evaluating the importance of glutathione peroxidase and selenium compounds independently of glutathione peroxidase for the protection against oxidative insult.

Cell Division↗
PubMed1987

Influence of glucose and buffer capacity in the culture medium on growth and pH in spheroids of human thyroid carcinoma and human glioma origin.

pH gradients were measured with microelectrodes in cellular spheroids of human glioma (U-118 MG) and thyroid carcinoma (HTh7) origin. pH decreased outside the spheroids and then continuously decreased when the electrode was moved through the spheroid towards the center. The lowest pH values inside the spheroids were in the range 6.7-6.8 when grown under standard conditions with F10 medium. When medium with stronger buffer capacity (Dulbecco's minimum essential medium or Locke's) was used, the gradients in both types of spheroids were less steep. Less steep pH gradients were also obtained in both types of spheroids when the concentration of glucose was lowered to 0.1 g/liter in the medium. In the case of HTh7 spheroids the low pH inside the spheroids under standard culture conditions seemed toxic because the growth rate increased when the spheroids were cultured under conditions giving higher central pH values (high buffer capacity or low glucose concentration). No such growth-stimulating effects could be seen for the U-118 MG spheroids. The growth rate of both types of spheroids was retarded when they were grown in medium with very high glucose concentration (10 g/liter). The thickness of the viable cell layer increased for HTh7 spheroids when the concentration of glucose was lowered to 0.1 g/liter. A decrease in the thickness of the viable layer of U-118 MG spheroids was observed when they were grown at a high glucose concentration (10 g/liter).

Acid-Base Equilibrium↗
PubMed1987

Salivary peroxidase: an important part of our defense against oxygen toxicity.

All living cells convert dioxygen (O2) into the toxic intermediates of oxygen reduction: superoxide radicals, hydrogen peroxide and hydroxyl radicals. The defense against these intermediates works on three levels: 1) the formation of the intermediates is prevented; 2) the intermediates are scavenged; 3) the damaged sites are repaired. Various parts of this defense are found intracellularly, in tissue fluid, in blood plasma and in the external secretions. In the mouth there is a special need for defense against hydrogen peroxide, because hydrogen peroxide is not only formed by bacteria colonizing the mucous membranes but also by the cells of the salivary glands. In saliva the most important part of this defense is salivary peroxidase, which detoxifies hydrogen peroxide in the presence of thiocyanate by converting it into hypothiocyanite, dioxygen and water. In addition, hypothiocyanite stops hydrogen peroxide production by the oral bacteria.

Free Radicals↗