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Biomedical subjects

G Siebert

Publications and source records attributed to G Siebert.

At least 19 recordsLinked to original sources
PubMed1991

[Clinical-experimental study of muscle activity of complete denture wearers with various prostheses before and after equilibration].

The present electromyographic investigations, which were carried out by patients with full dentures should show if the activity-situation of the masticatory muscles would change either using a new full denture without equilibration or using new full dentures with equilibration. Other questions were: Is it possible to classify the patients in such, who prefer the masseter muscles or the temporalis muscles during mastication? Exist a correlation between the preferred masticatory side and an increased activity of the same side masticatory muscles?

Adult↗
PubMed1990

[Comparison investigation of non-precious metal-synthetic resin bond on basis of new adhesives and the non-precious metal-ceramic bond].

The adhesive force was tested between the Silicoater and Sebond-MKV bonding systems and two Co Cr alloys. The tests were: The flexural strength-test, the tensile stress-test, the fracture test and the shear strength test. The ceramic veneering had worse results only in the flexural strength test compared with the two bonding systems. The bonding system Silicoater was in the tensile stress test and in the fracture test better than the Sebond MKV system. The bonding system Sebond-MKV showed better results in the flexural strength test and in the shear strength test than the Silicoater system. Differences in the results you could find between the test after dry air storing and saliva storing.

Adhesives↗
PubMed1989

Nutritional assessment in humans and rats of leucrose [D-glucopyranosyl-alpha(1----5)-D-fructopyranose] as a sugar substitute.

Leucrose [D-glucosyl-alpha(1----5)-D-fructopyranose], prepared by an enzyme-catalyzed transglycosidation from sucrose with greater than 99% purity, has previously been shown to be noncariogenic and was found in the present study to be apparently easily digestible when given to humans as a single oral dose of 100 g, or when fed to rats at a level of 35 g/kg body wt daily. Weanling rats fed a 25% leucrose diet grew as well as rats fed a diet containing 25% sucrose or corn starch. When 1 g of leucrose was given intravenously to adult rats, 70% of this disaccharide was excreted in the urine within 24 h, and feeding and drinking behavior of the rats was not altered. No adverse effects on their general health were observed. The substrate properties of leucrose for alpha-glucosidase from yeast and for carbohydrases from human jejunal mucosa were determined, and these data were then compared with those of maltose and sucrose. The cleavage rate of leucrose in vitro by human digestive carbohydrases was 31% that of maltose and 63% that of sucrose. Hydrogenated leucrose (leucritol) was cleaved 10 times slower, with a Michaelis constant close to that of leucrose. Blood glucose and fructose profiles in humans given leucrose per os tended to be lower than those in humans given sucrose, while insulin and C-peptide profiles were unaltered.

Administration, Oral↗
PubMed1989

Cariological assessment of leucrose [D-glucopyranosyl-alpha(1----5)-D-fructopyranose] as a sugar substitute.

Leucrose [D-glucosyl-alpha(1----5)-D-fructopyranose] prepared by microbial-enzymatic transglycosidation from sucrose, is the first alpha(1----5)-linked disaccharide which possesses excellent nutritional properties with regard to metabolic utilization and is well tolerated. The aim of the present work was to assess its cariogenic potential. Yeast invertase was shown to be inhibited by leucrose in a noncompetitive way, while hydrogenated leucrose (leucritol) acted as an activator. Plaque polysaccharide forming glucosyltransferases from Streptococcus cricetus AHT were not influenced by leucrose, but by leucritol. Essentially no acid formation was observed after incubation of leucrose with suspensions of human dental plaque, S. mutans NCTC 10449, Lactobacillus casei LSB 132 and Actinomyces viscosus Ny 1 No. 30. Leucrose was a competitive inhibitor of the acid formation from sucrose by S. mutans NCTC 10449 at neutral pH. Furthermore, leucrose inhibited at neutral pH considerably the uptake of sucrose by S. mutans NCTC 10449. The uptake of fructose and maltose was also inhibited but that of glucose not at all. In Cara rats as the animal model, leucrose was compared to sucrose and to corn starch for its cariogenic potential. In sharp contrast to the group fed with 30% sucrose, caries scores of the 30% leucrose group were not significantly different from the starch group. pH telemetry with an indwelling electrode in man proved lueucrose to be 'safe for teeth' since plaque pH did not drop below pH 5.7. Leucrose is a novel noncariogenic disaccharide and thus represents a highly promising sugar substitute for caries prevention.

Actinomyces↗
PubMed1989

[Comparative post-treatment evaluation of patients with pain-dysfunction syndrome].

It was the objective of this study to evaluate the effects of the changes assessed by clinical functional analyses before and after treatment on the subjective symptoms of 234 patients with TMJ disorders and facial pain. The results showed that the numbers of tender muscles and the changes in interincisal opening are more closely correlated with the subjective discomfort of the patients than the extent of interocclusal clearance or deviation during jaw opening.

Attitude to Health↗
PubMed1989

[Differentiation of existential guilt and compassion in relation to responsibility induction: a film experiment].

Feelings of existential guilt are assumed to depend on the perception of a causal relationship between one's own behavior or (privileged) situation and the disadvantages of others. By contrast, pity should not depend on such perceptions. This hypothesis, which has been supported so far only by correlational studies, was tested experimentally. Eighty students were shown a film about a developing country. The film was provided with four different comments, each representing one experimental condition (between-subjects design). Experimental factors were "amount of misery of the people shown" and "subject's responsibility for these peoples' conditions of life". As expected, subjects in the condition "misery and responsibility" reported higher feelings of guilt, though no more pity than subjects in the remaining three treatment conditions (experiment 1, n = 40). This mean difference, however, was statistically significant for men only. Contrary to our theoretical expectations--and to finding from other experiments on vicarious reparation--the induction of guilt had no effect on willingness to help a third party (experiment 2, n = 40). Possible reasons for this unexpected finding are suggested.

Adult↗
PubMed1988

[Stepwise study procedure of sugar substitutes--preliminary study with enzymes. 4. Glucosyltransferases of Streptococcus mutans AHT].

A continuous procedure for the simultaneous enzymatic measurement of the release of free fructose and glucose was adapted to the kinetic conditions of the synthesis of polysaccharides from sucrose by glucosyltransferases from Streptococcus mutans AHT. Initial velocities, Km of sucrose, and the efficiency of the formation of glucans from sucrose can be determined. Longtime incubations with the isolation of soluble and insoluble glucans as an established method were compared with the new procedure. As examples of the effect of sugar substitutes on glucosyltransferases, data on leucrose, nystose, Palatinit, xylitol, leucritol and polyglucose PL-3 are presented. The results provide a preliminary assessment of sugar substitutes such as non-cariogenic sweeteners.

Fructose↗
PubMed1988

Uptake of saccharin and related intense sweeteners by Streptococcus mutans NCTC 10449.

In a 1-octanol/phosphate buffer system, saccharin was much more lipophilic than would be inferred from its dissociation constant which, however, determined the partition behavior of acesulfame and cyclamate. The uptake of saccharin into Streptococcus mutans led to a 30 to 40-fold higher concentration of this intense sweetener within cells than in the incubation medium. Acesulfame and cyclamate were distributed between cells and medium essentially in a diffusion-controlled manner. The uptake of saccharin into S. mutans was found to depend strongly on simultaneous sugar fermentation, and in addition, on external pH, sweetener concentrations, and cell densities. Without glycolysis, caused, for example, by an exhaustion of added sucrose, too acidic external pH, or the addition of glycolysis inhibitors, the uptake of saccharin was diffusion-controlled as in the case of acesulfame and cyclamate. The uptake of saccharin was inhibited by a reversal of the direction of the lactate gradient from in----out to out----in. The activation energy of saccharin uptake into glycolyzing S. mutans was near 18 kJ/mol, while glycolysis itself required 82-98 kJ/mol as activation energy, depending somewhat on experimental conditions. Up to 100 attomol of saccharin per bacterial cell was observed. It was concluded that the cytomembrane of S. mutans was involved in mediating the inhibitory effects of saccharin by an antiport of saccharin into cells in exchange for lactate.

Chromatography, High Pressure Liquid↗
PubMed1987

On the occurrence of free glucose in the caecal contents of rats.

Free glucose was assayed in the caecal contents of rats. Whereas control animals had less than 60 nmol glucose per g of caecal contents, 230 nmol glucose/g caecal contents were determined 3 hours after the administration of 300 mg Palatinit by gastric intubation. In contrast to an earlier report (8), caecal fluid thus contained less than 3% of the glucose concentration of 11 mumol/ml claimed to occur after Palatinit administration by these authors (8). Since the anaerobic fermentation capacity for glucose by the caecal contents of rats amounted to at least 630 nmol glucose/min X g fresh weight at 37 degrees C, only the low glucose concentrations reported above are plausible.

Animals↗
PubMed1987

In vitro assessment of nystose as a sugar substitute.

Nystose represents a fructooligosaccharide with two fructose molecules linked via beta(1----2) bonds to the fructosyl moiety of sucrose. This tetrasaccharide was subjected to an array of in vitro tests designed for the assessment of potential sugar substitutes before animal or human studies. beta-Fructosidase from yeast cleaved nystose at about 5% of the initial rate observed with sucrose. The terminal fructose was released first. Glycosyltransferase from Streptococcus mutans #620 did not utilize nystose for the formation of a glucan-type polysaccharide. Anaerobic fermentation of nystose by a suspension of mixed dental plaque microorganisms and by S. mutans NCTC 10449 was about half as fast as with sucrose. Thin-layer chromatography at various reaction times with S. mutans NCTC 10449 indicated the terminal fructose as the site of first attack. Analyses for free monosaccharides confirmed these data because free fructose exceeded free glucose at early reaction times far more than would follow from the 3:1 ratio of fructose to glucose in the nystose molecule. High pressure liquid chromatography assays demonstrated lactic and acetic acids as the main fermentation products. Carbohydrases from human jejunal mucosa did not attack nystose. However, cecal anaerobic microorganisms of the rat fermented nystose rapidly into acids.

Animals↗
PubMed1987

Mitochondrial malic enzyme in human leukocytes.

Leukocyte samples from 316 unrelated blood donors were screened for malic enzyme (MEM). The frequency of the common allele in this investigation was MEM1 = 0.63. There is evidence for the existence of a rare fourth allele MEM4.

Humans↗
PubMed1986

[A stepwise method of evaluating sugar substitutes--a preliminary study using enzymes. 1. Alpha-glucosidase from yeast].

alpha-Glucosidase from yeast was checked for its catalytic potency under a variety of experimental conditions. Michaelis constants and maximal velocities are reported for 7 disaccharides of the glucosyl-fructosyl or glucosyl-glucosyl type, 4 disaccharide alcohols, and 2 mixtures of each 2 disaccharide alcohols. Reduction of a carbonyl group is of less importance for the substrate properties than the type of the glycoside bond; consequences for the suitability of potential sugar substitutes are derived.

Disaccharides↗