[Fracture mechanics design of dental gold soldered joints (author's transl)].
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Dental Occlusion↗
Biomedical subjects
J Carlsson
Publications and source records attributed to J Carlsson.
Symbiosis between host and microorganisms in the oral cavity.
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Bacteria↗
Protein-coated agarose surfaces for attachment of cells.
Plastic dishes were coated with an agarose layer. The layer was modified by covalently binding proteins to it, using the CNBr-method. Cells were seeded on the dishes and the number of attached cells was evaluated. The specificity of the attachment was demonstrated by showing that cells, carrying specific membrane-bound immunoglobulins, attached only to the corresponding anti-immunoglobulins. This indicated that the method could be used for cell sorting. The attachment of cells to proteins was influenced by the amount of bound protein, incubation time, temperature and the degree of trypsinization. Most attached cells were viable for several days and when dying they detached. Detailed morphological and cytochemical analyses of the dynamics of attachment and cytoplasmic spreading on the chemically well-defined surfaces were possible using the new method.
Burkitt Lymphoma↗
Bactericidal effect of cysteine exposed to atmospheric oxygen.
Peptostreptococcus anaerobius VPI 4330-1 was exposed to atmospheric oxygen in a dilution bland (0.2% gelatin, salts, resazurin) solution. The organisms were rapidly killed when the solution contained cysteine. The organisms were effectively protected by catalase and horseradish peroxidase as well as by the metal ion-chelating agents 8-hydroxyquinoline and 2,2'-bipyridine. Superoxide dismutase increased the rate of killing of the organisms, whereas singlet oxygen quenchers and scavengers of hydroxyl free radicals did not protect the organisms from the toxic effect of cysteine. Hydrogen peroxide was formed when cysteine was exposed to oxygen in the dilution blank solution, and the reaction was inhibited by metal ion-chelating agents. The organisms were rapidly killed by 20 microM hydrogen peroxide in anaerobic dilution blank solution. The toxic effect of hydrogen peroxide in anaerobic dilution blank solution. The toxic effect of hydrogen peroxide was completely abolished by catalase and metal ion-chelating agents. These results indicated that hydrogen peroxide was formed in the dilution blank solution in a metal ion-catalyzed autoxidation of cysteine and that hydrogen peroxide was toxic to P. anaerobius VPI 4330-1 in a reaction also catalyzed by metal ions.
Anaerobiosis↗
Bovine superoxide dismutase and copper ions potentiate the bactericidal effect of autoxidizing cysteine.
When cysteine is oxidized by oxygen, hydrogen peroxide is formed, and hydrogen peroxide is very toxic to Peptostreptococcus anaerobius VPI 4330-1. Native and inactivated superoxide dismutase increased the rate of oxidation of cysteine and thereby potentiated the toxic effect of cysteine. A similar increase in the rate of oxidation of cysteine and in the toxicity of cysteine was obtained with Cu2+.
Aerobiosis↗
Age dependent changes in the metabolism of 3H-thymidine and 3H-uridine in young rats.
The metabolism of subcutaneously injected 3H-thymidine and 3H-uridine was studied in 5, 15 and 30-day-old rats and some age-dependent differences were found. The total availability of 3H-uridine was found to decrease when the rats became older. In the case of 3H-thymidine, however, there was only minor differences in the total availability. The catabolism of both 3H-thymidine and 3H-uridine, as measured by the appearance of 3H-water, was more efficient when the rats became older. In the case of 3H-thymidine, however, the increased catabolic capacity seems to be compensated by a decreased proliferative growth so the total availability will be constant. It was also observed that the amount of intermediate catabolic products in the blood was much larger after an injection of 3H-uridine than after 3H-thymidine.
Aging↗
Protein thiolation and reversible protein-protein conjugation. N-Succinimidyl 3-(2-pyridyldithio)propionate, a new heterobifunctional reagent.
A heterobifunctional reagent, N-succinimidyl 3-(2-pyridyldithio)propionate, was synthesized. Its N-hydroxysuccinimide ester group reacts with amino groups and the 2-pyridyl disulphide structure reacts with aliphatic thiols. A new thiolation procedure for proteins is based on this reagent. The procedure involves two steps. First, 2-pyridyl disulphide structures are introduced into the protein by the reaction of some of its amino groups with the N-hydroxysuccinimide ester sie of the reagent. The protein-bound 2-pyridyl disulphide structures are then reduced with dithiothreitol. This reaction can be carried out without concomitant reduction of native disulphide bonds. The technique has been used for the introduction of thiol groups de novo into ribonuclease, gamma-globulin, alpha-amylase and horseradish peroxidase. N-Succinimidyl 3-(2-pyridyldithio)propionate can also be used for the preparation of protein-protein conjugates. This application is based on the fact that protein-2-pyridyl disulphide derivatives (formed from the reaction of non-thiol proteins with the reagent) react with thiol-containing proteins (with native thiols or thiolated by, for example, the method described above) via thiol-disulphide exchange to form disulphide-linked protein-protein conjugates. This conjugation technique has been used for the preparation of an alpha-amylase-urease, a ribonuclease-albumin and a peroxidase-rabbit anti-(human transferrin) antibody conjugate. The disulphide bridges between the protein molecules can easily be split by reduction or by thiol-disulphide exchange. Thus conjugation is reversible. This has been demonstrated by scission of the ribonuclease-albumin and the alpha-amylase-urease conjugate into their components with dithiothreitol. N-Succinimidyl 3-(2-pyridyldithio)propionate has been prepared in crystalline form, in which state (if protected against humidity) it is stable on storage at room temperature (23 degrees C).
Chemical Phenomena↗
Physical and nutritional factors in gel culture of mammalian cells.
The growth of human glioma cells, cultured as spherical colonies in agarose gel, stopped after about 10 days for both large and small colonies apparently due to an increased osmolality in the gel. When osmolality was kept under control by addition of distilled water, growth continued. However, a continuous increase in the population-doubling period, similar for both large and small colonies, then was observed. The increase persisted although excess amounts of nutrition were added. When the cells were cultured in liquid suspension above a thin layer of agarose gel and most of the medium was repeatedly changed, the colonies continued to grow beyond the limits in gel cultured. HeLa and hamster embryonic lung cell colonies showed a growth pattern in agarose gel similar to the glioma cells. The results imply that the osmolality must be kept under precise control to prevent growth inhibition. However, it seems difficult to ascertain optimal growth in gel culture for more than about 2 weeks probably because of the accumulation of toxic products.
Animals↗
Plasma membrane motility and proliferation of human glioma cells in agarose and monolayer cultures.
Human glioma cells, growing as spherical colonies in agarose gel, or as monolayers on glass or plastic, were studied with time-lapse cinematography and electron microscopy. The cells in the agarose cultured colonies often had ruffling-like membrane structures which were similar in for, although smaller in size, than those observed on monolayer cultured cells. The ruffling-like structures were more frequent at the periphery than in the central regions of the colonies which was in parallel to the proliferative pattern. In time-lapse cinematography it was seen that pinocytotic vacuoles were formed from ruffling membranes in the monolayer cultures. In the transmission electron microscope, such vacuoles were also found near the ruffling-like structures in the agarose cultured cells. In dense monolayer cultures, ruffling and associated pinocytosis were to a large extent transferred from the margin to the upper surface of the cells. This capacity may be an important property for the ability of the malignant cells to attain extreme high cell densities in monolayer cultures and to grow as colonies in agarose cultures. As has been previously shown, the normal counterpart of the gliomas, the glia cells, cannot grow to high densities; they do not ruffle on their upper cell surface and are unable to grow in suspension or agarose culture.
Autoradiography↗
Hydrogen peroxide and superoxide radical formation in anaerobic broth media exposed to atmospheric oxygen.
Fourteen different broth media were autoclaved under anaerobic conditions and then exposed to atmospheric oxygen. The hydrogen peroxide and superoxide radical formation as well as the bactericidal effect of the media were studied. The rate of killing of Peptostreptococcus anaerobius VPI 4330-1 was high in media that rapidly autoxidized and accumulated hydrogen peroxide. In actinomyces broth (BBL), 50% of the cells were killed within 2 min, and in Brewer thioglycolate medium (Difco), 50% were killed within 11 min, whereas more than 50% of the cells survived for more than 2 h in Clausen medium (Oxoid), fluid thioglycolate medium (BBL), and thioglycolate medium without dextrose or indicator (Difco). Only media that contained phosphate and glucose had a tendency to accumulate hydrogen peroxide. A solution of phosphate and glucose autoxidized when it had been heated to 120 degrees C for at least 5 min and when the pH of the solution was higher than 6.5. Transitional metal ions catalyzed the autoxidation, but they were not necessary for the reaction to occur. Of the other substances heated in phosphate buffer, only alpha-hydroxycarbonyl compounds autoxidized with accumulation of hydrogen peroxide. Superoxide dismutase decreased the autoxidation rate of most of the broth media. This indicated that superoxide radicals were generated in these media.
Anaerobiosis↗
Proliferation and viability in cellular spheroids of human origin.
The capacity of cells to form growing tumor-like colonies in culture was tested by a new and unlaborious suspension technique. Six of nine tested cell lines formed spheroids, five of which started to grow. The growing spheroids reached a maximal size determined by balanced cell gain in a proliferative, superficial layer and cell death, particularly at larger depth. Sections of spheroids of different origin showed large variations in the thickness of the viable cell layers and in the shape of the proliferative gradients. The data, taken together with earlier published information, indicate that a difference between rodent and human cells generally exists, the former showing thinner viable and proliferative layers.
Animals↗
A proliferation gradient in three-dimensional colonies of cultured human glioma cells.
The growth of colonies of human glioma cells cultured in agarose has been studied. The mitotic activity and the fraction of cells which incorporated tritiated thymidine decreased nearly exponentially with the depth in the colonies, the shape and inclination of the proliferation gradient being independent of the colony diameter. This explains why the volume doubling times were rather similar for colonies of different sizes. It is also shown that the stability of the gradient during growth gave rise to nearly exponential growth, although a large part of the centrally situated cells were out of the cell cycle or had a reduced proliferative rate. The incorporation of tritiated thymidine into labelled cells was similar in the peripheral and the central regions as evaluated from grain counting. This indicated that the length of the S-phase was constant.
Cell Division↗
Isolation of lactoferrin from human milk by metal-chelate affinity chromatography.
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Biological Assay↗
Specific isolation of cysteine peptides by covalent chromatography on thiol agarose derivatives.
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Chromatography, Affinity↗
Effects of bacterial agarase on agarose gel in cell culture.
Bacterial agarase, concentrated and purified from culture filtrate of agar-degrading bacteria, has been used to clean cells cultured in soft agarose from gel residues. The enzyme also has been used to liquefy the gel directly in the dishes to facilitate the removal of cells. The sufaces of glioma cells from agarase-treated colonies could not be distinguished in the scanning electron microscope from surfaces of cells which had never been in contact with agarose or agarase. This implies that most agarose residues had been removed, and also that the treatment did not seriously alter the cell surfaces. The influence of the agarase treatment also was tested by comparison of the mitotic index and the incorporation of [3H]thymidine in agarase-treated and untreated cells. No effects of the treatment could be seen in these tests.
Bacteria↗
Purification of uricase by biospecific adsorption-desorption.
A simple procedure for the purification of uricase from bovine kidney is described. The procedure involves the following steps: 1) processing of kidney mince by borate/butanol, 2) ammonium sulphate precipitation, and 3) biospecific adsorption-desorption. The adsorbents were prepared by chemical attachment of urate or xanthine to agarose gel beads. The desorption was performed by a xanthine solution. The adsorption-desorption procedure resulted in an 11 000-12 000-fold purification. The specific activity of the purified uricase was 19.8 U/mg using either "urate" adsorbent. The recovery was about 70%. The adsorbents were also used for the purification of commercial uricase preparations from hog liver. In this case the purified uricase also possessed a specific activity of 19.8 U/mg. The products were homogenous as judged by gradipore electrophoresis and gel filtration.
Adsorption↗
The fine structure of three-dimensional colonies of human glioma cells in agarose culture.
The fine structure of human glioma cells cultivated as three-dimensional colonies in agarose was investigated during exponential growth. The colonies did not show central degeneration, although they reached diameters of up to 600 mum. Large extra-cellular spaces extended throughout the colonies. The mean volumetric fraction of the spaces increased from about 20 per cent at the periphery up to nearly 40 per cent in the central regions. The quotient between nuclei and cytoplasm showed a slight decrease with depth. A proliferative gradient existed in the colonies, i.e. the mitotic index decreased almost exponentially with the distance from the surface. The distance at which the mitotic index changes by a factor of 2 was about 90 mum, corresponding to nearly five cell diameters. Cytoplasmic extensions, with a ruffling-like appearance, occurred both at the periphery and in the centre of the colonies but were larger and more frequent at the periphery. The fractions of mitochondria and vacuoles in the cytoplasm showed rather large local variations. However, the mean number of mitochondria decreased somewhat towards the centre and the number of vacuoles containing highly electron-absorbing substance increased in the most central regions.
Cell Aggregation↗
Bactericidal effect of anaerobic broth exposed to atmospheric oxygen tested on Peptostreptococcus anaerobius.
Peptostreptococcus anaerobius strain VPI 4330-1 was used as the test organism in an evaluation of the bactericidal effect of anaerobic broth exposed to air. The test organism, grown under anaerobic conditions in Trypticase soy broth, was diluted in buffered salt solution, and about 2 x 10(4) cells were suspended in 10 ml of an aerated broth. Ninety percent of the cells were killed within 15 min in actinomyces broth and within 50 min in Trypticase soy broth. All cells survived for 2 h in fluid thioglycolate medium. Addition of DABCO [1,4-diazabicyclo (2.2.2) octane] or mannitol to Trypticase soy broth did not influence the death rate of the organism, whereas superoxide dismutase decreased the death rate. Addition of catalase or manganese dioxide to the broth kept all the cells viable for 2 h. Of the three broth media tested, actinomyces broth reduced oxygen at the highest rate and Trypticase soy broth reduced it at the slowest rate. Hydrogen peroxide could be demonstrated in actinomyces broth and in Trypticase soy broth but not in fluid thioglycolate medium. In addition to catalase, manganese dioxide also removed all hydrogen peroxide from Trypticase soy broth, and superoxide dismutase significantly decreased the concentration of hydrogen peroxide in the broth. The results suggest that hydrogen peroxide mediated the toxic effect of atmospheric oxygen in these broth media.
Anaerobiosis↗