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Biomedical subjects

T Berg

Publications and source records attributed to T Berg.

At least 307 records · Page 17Linked to original sources
PubMed1981

Binding, uptake, and degradation of 125I-labelled high-density lipoproteins in isolated non-parenchymal rat liver cells.

Binding, uptake, and degradation of 125I-labelled HDL were measured in isolated rat non-parenchymal cells in vitro. The binding exhibited saturation kinetics and was inhibited to various degrees with other unlabelled lipoproteins such as VLDL, LDL, and HDL, but the uptake was not reduced by heat and formaldehyde-denatured albumin. The binding could be reduced by pronase treatment of the cells. Acetylated 125I-labelled HDL were more effectively taken up and degraded by non-parenchymal cells than unmodified 125I-labelled HDL. The Kupffer cells were able to take up two to three times as much HDL per cell as the endothelial cells. 125I-labelled HDL bind to the plasma cell membrane and can be dissociated by addition of unlabelled HDL. Relatively more labelled HDL dissociate at 4 degrees C than at 37 degrees C. The non-parenchymal cells also internalize 125I-labelled HDL at 37 degrees C, and the lysosomotropic drug chloroquine inhibits partly the degradation of accumulated 125I-labelled HDL.

Animals↗
PubMed1980

The intracellular distribution of high density lipoproteins taken up by isolated rat hepatocytes.

The subcellular distribution of 125I-labelled HDL taken up by rat hepatocytes in vivo and in vitro has been studied with subcellular fractionation techniques: differential centrifugation and isopycnic centrifugation in sucrose gradients. 125I-labelled HDL bind to plasma membranes both in vivo and in vitro and part of the membrane-bound 125I-labelled HDL can be dissociated by the addition of unlabelled HDL. The hepatocytes also internalize 125I-labelled HDL. The 125I-labelled HDL accumulate, however, at different intracellular sites in the in vivo and in vitro situation. The subcellular distribution pattern of 125I-labelled HDL taken up by the cells in vivo is similar to that of the lysosomal marker enzyme acid phosphatase. Peak activity was found at a density of 1.20 g/ml. In vitro 125I-labelled HDL accumulate in an organelle with a medium density of about 1.13 g/ml. This distribution was similar to that of the plasma membrane marker 5'-nucleotidase. The subcellular distribution of radioactivity taken up in vivo was changed to lower density by incubating the cells with chloroquine, a drug known to render the lysosomes more boyant. Chloroquine had no effect on the distribution of 125I-labelled HDL taken up by hepatocytes in vitro.

5'-Nucleotidase↗
PubMed1980

Binding of concanavalin A to isolated hepatocytes and its effect on uptake and degradation of asialo-fetuin by the cells.

1. The binding of 125I-labelled concanavalin A to isolated rat hepatocytes was studied at temperatures between 4 degrees C and 37 degrees C. At the latter temperature, concentrations of concanavalin A from 0.01 to 0.4 mg/ml were used. In all of these experiments, binding reached a plateau after 40--60 min, when 28--35% of the concanavalin A added was bound to the cells (cell density 8 x 10(6) cells/ml). 2. The rate of uptake of 125I-labelled asialo-fetuin by the hepatocytes was lowered to 30% of control values when the cells were preincubated with 0.1 mg of concanavalin A/ml. This decrease could be accounted for by a decrease in the rate of binding of asialo-fetuin to the beta-galactoside receptor of the cells. The binding capacity of the cells was not influenced by preincubation with concanavalin A. 3. Degradation of asialo-fetuin was decreased only if concanavalin A was present during the uptake of asialo-fetuin by the cells. Subcellular fractionation revealed that concanavalin A lowered the rate of entry of endocytosed asialo-fetuin into the lysosomes. The effect of concanavalin A on degradation is distinct from its effect on the rate of uptake of asialo-fetuin by hepatocytes.

Animals↗
PubMed1980

Cesarean section in premature delivery.

Cesarean sections were performed in 24 cases before the end of the 32nd week of pregnancy. Despite the fact that the indications for the operations were severe obstetric complications, the perinatal mortality was 25%, which should be compared to 23% for all children born in Sweden at that age., 2 of the surviving children developed definite neurological sequelae, which is a lower incidence than reported for vaginal premature deliveries. The results indicate that cesarean section can be recommended even for deliveries before the end of the 32nd week of pregnancy for fetal indications such as breech presentation, premature rupture of the membranes, premature labor with rigid cervix and for fetal asphyxia.

Apgar Score↗
PubMed1980

Investigation of the uptake of asialo-glycoproteins by isolated rat hepatocytes. Implications for its biological significance.

The uptake of asialo-glycoproteins, asialo-fetuin and asialo-orosomucoid, was studied in isolated rat hepatocytes. The total binding capacity for either of these asialo-glycoproteins was 150 000 molecules per cell. The association constants were 0.98 x 10(8) M-1 (asialo-fetuin) and 4.8 x 10(8) M-1 (asialo-orosomucoid) at 10 degrees C. At 37 degrees C, the affinity of asialo-transferrin for the receptor was approximately 1/300 of that of asialo-fetuin. The uptake process was sensitive to neuraminidase, the effect being measurable at 0.5 mU/ml. At 10 mU/ml, the uptake was 15% of that in control cells. The uptake was at the same level when the cells were washed to remove neuraminidase before the addition of asialo-glycoprotein. Lowering the concentration of calcium ions below 2 mM reduced the affinity of the receptor, as addition of an excess of EGTA led to rapid release of asialo-glycoprotein from the cells. The fraction which was released was low when the cells had been incubated with asialo-glycoprotein at 37 degrees C before the addition of EGTA; nearly all of the cell-associated asialo-glycoprotein could be released if the cells had been incubated at 10 degrees C. At 10 degrees C as well as 37 degrees C, the uptake declined sharply when the concentration of calcium ions in the medium was lowered from 0.5 mM to 0.05 mM.

Animals↗
PubMed1980

Kinetics of internalization and degradation of asialo-glycoproteins in isolated rat hepatocytes.

The rate constants for internalization of surface-bound asialo-orosomucoid by hepatocytes were 0.040 min-1 at 20 degrees C, 0.18 min-1 at 30 degrees C and 0.28 min-1 at 40 degrees C. At 40 degrees C, internalization accounted for most of the increase in cell-associated radioactivity. The activation energy over the temperature range 20 to 40 degrees C was 68 +/- 7 (S.D.) kJ/mol. At 10 degrees C, most of the cell-associated asialo-orosomucoid was bound to the cell surface in a reaction which followed ordinary chemical kinetics. Pre-incubation of hepatocytes with a large concentration of unlabelled asialo-orosomucoid did not influence the uptake of subsequently added 125I-asialofetuin; neither was degradation of 125I-asialo-fetuin affected in this experiment. The fractional rate of degradation (the fraction of cell-associated asialo-fetuin which was degraded per unit time) was constant over a twelve-fold range of intracellular asialo-fetuin concentrations. Increasing the temperature from 20 to 30 degrees C produced approximately a ten-fold increase in the rate of degradation of either asialo-fetuin or asialo-orosomucoid. The average activation energies of degradation over the range 20 to 40 degrees C were 125 kJ/mol for asialo-fetuin and 149 kJ/mol for asialo-orosomucoid; however, the Arrhenius plots were not straight lines over this temperature range.

Animals↗
PubMed1980

Clinical studies of a purified timothy pollen extract. Desensitization therapy with a purified timothy pollen preparation compared to a crude timothy pollen extract. I. Results of tests in vivo.

A purified freeze-dried preparation of timothy pollen was compared with a crude extract in RAST, skin tests, conjunctival provocation tests and desensitization treatment. In 48 children with grass pollen allergy a thorough allergological investigation was performed, using the two allergen preparations in different tests. The purified preparation contained relevant allergens, as judged from the good agreement between the two extracts in prick and provocation tests. The freeze-dried purified extract had good storage stability. Desensitization treatment was found to have a significant effect, as judged by repeated prick and provocation tests with both extracts. The effect of the desensitization treatment was at least as good in the children treated with the purified preparation as in those treated with the crude extract.

Adolescent↗
PubMed1979

Uptake and degradation of 125I-labelled high density lipoproteins in rat liver cells in vivo and in vitro.

1. The uptake of 125I-labelled high density lipoproteins (HDL) in various organs of the rat was determined after an intravenous injection. The uptake of 125I-labelled polyvinylpyrrolidone in the same organs was determined in order to assess uptake by fluid endocytosis. The uptake/organ was highest for the liver. The adrenals showed the highest uptake/unit weight of the organs studied. The liver, the kidneys and the spleen showed comparable values for uptake/g of tissue. The uptake of 125I-labelled HDL exceeded by far that of 125I-labelled polyvinylpyrrolidone in the liver, the kidneys, the spleen and the adrenals, indicating that the uptake of 125I-labelled HDL was mediated by adsorptive endocytosis. 2. The in vivo uptake of 125I-labelled HDL was determined in purified hepatocytes and non-parenchymal cells prepared by collagenase perfusion of livers from animals after intravenous injections of 125I-labelled HDL. When expressed per cell, the hepatocytes and the non-parenchymal liver cells took up about the same amount of 125I-labelled HDL. 3. The in vitro uptake and degradation of 125I-labelled HDL in isolated rat hepatocytes was studied. The uptake at increasing concentrations of 125I-labelled HDL was saturable indicating uptake mediated through binding sites. 125I-labelled HDL were easily degraded by contaminating proteases from the perfusate. 4. Subcellular fractionation by isopycnic centrifugation indicated that the accumulation of 125I-labelled HDL did not take place in the lysosomes, but rather on the plasma membrane and possibly in the endosomes (phagosomes). 5. 125I-labelled HDL were internalized into the cells and degraded in the lysosomes. Leupetin and chloroquine, inhibitors of the lysosomal function effectively inhibited the formation of 125I-labelled acid-soluble radioactivity by the cells. Chloroquine, but not the protease inhibitor leupeptin, reduced the hydrolysis of the cholesteryl ester moiety of HDL.

Animals↗
PubMed1979

Intracellular localization and degradation of asialofetuin in isolated rat hepatocytes.

Analysis by isopycnic and differential centrifuging of the intracellular distribution of radioactivity following uptake of 125I-labelled asialofetuin by isolated rat hepatocytes showed that during incubations up to 1 h, most of the radioactivity was associated with structures which had a subcellular distribution pattern different from both the lysosomes and the plasma membrane. The latter two organelles were followed by means of enzyme markers. Ca2+ is necessary for the binding of asialofetuin to the plasma membrane, and it was also possible to differentiate between asialofetuin bound to the plasma membrane and that contained in intracellular structures by removing Ca2+ from the medium (by EGTA). Such experiments showed that asialofetuin became rapidly internalized. Practically all the labelled protein was located intracellularly in cells that had been incubated with asialofetuin for more than 30 min. When incubations were carried out for more than 1 h a peak appeared in the radioactivity distribution in the same place as the peak of activity of lysosomal marker enzymes. However, degradation of asialofetuin takes place in the lysosomes and this starts before the labelled protein can be found in the lysosomal fractions. Our data suggest that the rate-determining step in the cellular handling of asialofetuin is the transport of endocytized protein from the endocytic vesicles to the lysosomes.

Animals↗
PubMed1979

I-bar: myth and countermyth.

An attempt has been made to stress the importance of removable partial denture design totality and to clarify the relationship of other major components to I-bar retainer usage. As outlined in this article, I-bar retainer usage is only one part of a given, comprehensive design philosophy. Its successful use has been shown to be as much based on proper application as upon appropriate, defensible design. There is no realistic concept of a simple I-bar partial denture just as there has never been one "technique" that serves as a panacea for all treatment situations.

Dental Abutments↗