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Biomedical subjects

T Berg

Publications and source records attributed to T Berg.

At least 325 records · Page 18Linked to original sources
PubMed1978

Anterior rests for maxillary removable partial dentures.

Positive anterior rests were shown to be an essential element of design when considering stress distribution with a removable partial denture involving anterior teeth. Proximal plates often added stability and reduced stress accumulation in any one region. Distobuccal forces on the extension base adversely affected the primary canine abutment. Forces in the regions of the anterior base and central incisor abutment produced the most widespread transmission of stress throughout the arch. Greater stress throughout the arch was observed when forces were applied to the central incisor rather than to the right canine abutment. There is a need for established criteria of rest form and placement. Guidelines for using the natural crown as opposed to a positive rest seat in a restoration are needed. Continuing studies of other anterior rest forms should increasingly clarify this phase of treatment planning. The dentist should recognize the need for structural integrity in the anterior maxillary segment when designing removable partial dentures. A practical, defensible rationale for the routine use of maxillary anterior teeth as removable partial denture abutments must be established.

Dental Abutments↗
PubMed1977

Uptake and degradation of 125I-labelled asialo-fetuin by isolated rat hepatocytes.

125I-Labelled asialo-fetuin was taken up by isolated rat hepatocytes by a saturable process. Half maximum uptake was seen at about 3 - 10(-8) M asialo-fetuin. Non-parenchymal liver cells did not take up asialo-fetuin in vitro. Rate of uptake of asialo-fetuin exceeded rate of degradation at all concentrations of asialo-fetuin tested. Asialo-fetuin consequently accumulated in the cells until the extracellular supply was exhausted. Asialo-fetuin degradation could be studied without concurrent uptake by incubating cells, previously exposed to asialo-fetuin, in asialo-fetuin-free medium. Degradation, as evidenced by increase in acid-soluble radioactivity, was inhibited by NH4Cl and chloroquine. The change with time in the intracellular distribution pattern of radioactivity in cells that had been exposed to 125I-labelled asialo-fetuin for 10 min was examined by means of differential centrifugation. Initially, the radioactivity was found mostly in the microsomal fraction. 60 min after the exposure to labelled protein, the distribution pattern of radioactivity resembled that of the lysosomal enzyme beta-acetylglucosaminidase. The possibility that asialo-fetuin digestion takes place in lysosomes is discussed.

Ammonium Chloride↗
PubMed1977

Uptake and degradation of cholesterol ester-labelled rat plasma lipoproteins in purified rat hepatocytes and nonparenchymal liver cells.

1. A new method for isolation and purification of rat liver hepatocytes and nonparenchymal cells by differential centrifugation is described. 2. Cholesterol ester-labelled lipoproteins (prepared by the action of lecithin: cholesterol acyltransferase) intravenously injected were taken up by hepatocytes and nonparenchymal cells. 3. Hepatocytes and nonparenchymal cells in suspension were able to take up and hydrolyse the cholesterol ester portion of lipoproteins. 4. Uptake of cholesterol ester labelled whole rat plasma and high density lipoproteins (HDL) increased with increasing concentrations until a distinct saturation level was reached in hepatocytes. In nonparenchymal cells there was no saturation of lipoprotein uptake. 5. Concanavalin A inhibited cholesterol ester-labelled lipoprotein uptake in hepatocytes, indicating that the uptake at least partially depends on carbohydrate sites on the cell surface. The uptake in nonparenchymal cells was unaffected of concanavalin A. 6. The specific activity of the acid cholesterol ester hydrolase was the same in homogenates from hepatocytes and nonparenchymal cells while acyl-CoA: cholesterol acyltransferase was found almost exclusively in hepatocytes.

Acid Phosphatase↗
PubMed1977

Uptake and degradation of formaldehyde-treated 125I-labelled human serum albumin in rat liver cells in vivo and in vitro.

The uptake of formaldehyde-treated 125I-labelled human serum albumin in rat hepatocytes and nonparenchymal liver cells was measured in vivo and in vitro. Isolated liver cells were prepared by treating the perfused liver with collagenase. Purified hepatocytes and nonparenchymal cells were obtained by differential centrifugation. Human serum albumin was found to be taken up exclusively or almost exclusively by nonparenchymal cells in vitro and in vivo (after intravenous injection). The maximal rate of human serum albumin-uptake in vitro was comparable to that in vivo. Nonparenchymal cells degraded human serum albumin in vitro as indicated by release of trichloroacetic acid-soluble radioactivity. Degradation started about 20-30 min after addition of human serum albumin to cells and rate of degradation was proportional to rate of uptake. Human serum albumin-degradation could be studied without interference of concurrent uptake by separating cells that had been preincubated with human serum albumin from the medium and then reincubating them with human serum albumin-free medium. The lag phase before human serum albumin-degradation starts and the inhibitory effect of chloroquine on degradation indicate that human serum albumin is degraded in lysosomes. The data obtained show that enzymatically prepared nonparenchymal liver cells retain their endocytic activity in vitro. Denatured human serum albumin should be useful both as a marker for rat liver macrophages and for the study of intracellular proteolysis in these cells.

Animals↗
PubMed1977

Scanning electron microscopic surface morphology of isolated hepatocytes from normal and premalignant rat liver.

Scanning electron microscopy was performed on hepatocytes isolated after collagenase perfusion of livers from rats fed 2-acetylaminofluorene (AAF) in the diet for 6--8 weeks and on hepatocytes from control rats. The premalignant AAF-cells showed a greater variation in cell size and shape. They also exhibited a reduced number of microvilli and more blebs and other protrusions on the surface than hepatocytes from control animals.

2-Acetylaminofluorene↗
PubMed1977

The effect of D-galactosamine on LCAT secretion and ultrastructure of isolated rat hepatocytes.

The effect of D-galactosamine on secretory activity and morphology of isolated rat hepatocytes was investigated: Galactosamine was found to reduce the secretion of lipoproteins (as indicated by the release of free cholesterol and triacylglycerol) as well as the secretion of lecithin: cholesterol acyltransferase (LCAT) and [14C]-labelled proteins from the isolated cells. The secretion of LCAT was inhibited much more than that of the other secretory products studied. Transmission electron microscopy revealed that galactosamine induced morphological changes in RER, mitochondria and nucleoli. The most striking feature of galactosamine-treated hepatocytes, however, was the appearance of swollen lysosomes. Some of these organelles measured up to 3 mumicrometer in diameter. Uridine did not abolish the effect of galactoosamine upon the secretory activity of hepatocytes. The most conspicuous ultrastructural feature in cells that had been incubated with both uridine and galactosamine was the appearance of large amounts of glycogen. The possibility that galactosamine inhibits glycogenolysis is discussed. The rather selective effect of galactosamine on LCAT secretion suggests the use of this compound for the study of the interrelationship between LCAT and lipoprotein secretion.

Animals↗
PubMed1977

Group B beta-hemolytic streptococci as an important cause of perinatal mortality.

Bacteriological and pathological examinations of all 73 stillborn infants and 96 infants dying soon after delivery in Västerås, Sweden during the period 1971-1974 are reported. 35 infants had a severe infection. Beta-hemolytic streptococci group B were isolated in 7 cases from different organs. Intrauterine death occurred in 2 cases; 4 liveborn infants showed early signs of respiratory distress, apneic episodes and cyanosis; 1 infant showed signs of intrauterine asphyxia and was severely asphyctic at birth. Thus, infection with group B streptococci occurred in 20% of the infants who succumbed to infections during this period.

Adult↗
PubMed1977

Uptake and degradation of asialo-fetuin by isolated rat hepatocytes.

125I-labelled asialo-fetuin was taken up by isolated rat hepatocytes by a saturable process. Half maximum uptake was seen at about 3 . 10(-8) M asialo-fetuin. Rate of uptake of asialo-fetuin exceeded rate of degradation at all concentrations of asialo-fetuin tested. Degradation of asialo-fetuin, as indicated by release of acid-soluble radioactivity from the cells, was inhibited by NH4Cl and chloroquine. The intracellular distribution of labelled asialo-fetuin was studied by differential and density gradient centrifuging. The distribution curves for radioactivity indicated that asialo-fetuin was present in lysosomes about 1 h after the uptake had started. Chloroquine and ammonium ions seemed to inhibit the uptake of asialo-fetuin into the lysosomes, possibly by interfering with the fusion between phagosomes and lysosomes.

Acetylglucosaminidase↗
PubMed1976

Secretion of lecithin: cholesterol acyltransferase from isolated rat hepatocytes.

1. Lecithin:cholesterol acyltransferase is secreted from isolated rat heptocytes. 2. The secretion is stimulated when serum is added to the incubation medium. 3. Optimal conditions for secretion are: 5-10(6) hepatocytes per ml, 5 h incubation, pH 7.3-7.4 and 25% serum in the incubation medium. 4. Concomitantly with the secretion of lecithin:cholesterol acyltransferase there is a secretion of unesterified cholesterol and triacylglycerol. 5. Colchicine or cycloheximide in the incubation medium inhibits secretion of lecithin:cholesterol acyltransferase.

Acyltransferases↗
PubMed1976

The influence of infection on the content of lysosomal enzymes in rat Kupffer cells and hepatocytes.

The activities of beta-glucuronidase, arylsulphatase A and acid DNAase were measured in homogenates from Kupffer cells and hepatocytes prepared from germ-free, monocontaminated and conventional rats. The cells were prepared from a liver cell suspension obtained by treating the perfused liver with collagenase. Kupffer cells from germ-free rats were found to have lower lysosomal enzyme activities than cells obtained from conventional rats. Monocontaminated animals (E. coli or Streptococcus pyogenes) showed intermediate activities. Our data indicate that the level of lysosomal enzymes in macrophages is a function of the endocytic activity of these cells.

Animals↗
PubMed1976

K+ transport in isolated rat liver cells stimulated by glucagon and insulin in vitro.

Unidirectional K+ fluxes were measured in suspensions of isolated rat liver parenchymal cells incubated with 42K+ in vitro. By tracer exchange analysis fluxes in both directions were estimated to 8-9 10(-12) mol/cm2. Glucagon in concentrations above 2 x 10(-8) M increased both influx and efflux to 160% of control values. Insulin increased influx by 12-14%, whereas efflux was apparently unaffected. Using an extracellular marker 51Cr EDTA, intracellular level of some ions was estimated in isolated liver cells: K+ = 172 mmol/kg water, Na+ = 25 mmol/kg water, Cl = 53 mmol/kg water. Cellular water content: 60%. Incubation with insulin for 1 h increased the intracellular concentration of K+ 1.7 mmol/kg water. The results indicate that glucoagon increased primarily the K+-permeability of the cell membrane, while insulin stimulates active K+ transport into the cell.

Animals↗
PubMed1976

Influence of insulin on lysosomal activity and urea production in isolated parenchymal cells from rat liver.

Non-latent (free) activities of two lysosomal enzymes (acid phosphatase and beta-glucuronidase) and urea production were measured in purified rat liver parenchymal cells incubated in the presence and absence of insulin. Non-latent enzyme activity was measured by including 0.25M sucrose in the assay mixtures to provide osmotic protection to the lysosomes. Total enzyme activity was estimated with Triton X-100 in the homogenates. Insulin was found to inhibit ureogenesis and to reduce non-latent lysosomal enzyme activity in the hepatocytes in vitro. Our data support the idea that insulin inhibits autophagy in rat liver parenchymal cells. Such an effect of insulin may also explain the inhibitory action of insulin on urea production in the rat liver.

Acid Phosphatase↗