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Biomedical subjects

L Linder

Publications and source records attributed to L Linder.

At least 109 records · Page 6Linked to original sources
PubMed1980

Regulation of synthesis of beta-fructofuranosidase (invertase) in Streptococcus mitis.

beta-Fructofuranosidase activity was found to be cell-bound in Streptococcus mitis ATCC 903. The following evidence suggests that induction functions as a regulatory mechanism for beta-fructofuranosidase in S. mitis: (1) on transfer of glucose-grown exponential phase bacteria to sucrose medium, the specific activity of beta-fructofuranosidase increased fourfold in the course of one generation; (2) other sugars had no stimulatory effect on the rate of synthesis of beta-fructofuranosidase; (3) the effect of sucrose on the rate of synthesis of beta-fructofuranosidase could be measured within a few minutes. Glucose, fructose and mannose repressed beta-fructofuranosidase. The addition of glucose to bacteria growing on sucrose repressed beta-fructofuranosidase for about one generation. The intracellular concentration of glucose was considerably increased during repression, while the intracellular concentration of glycolytic intermediates did not vary significantly.

Carbohydrate Metabolism↗
PubMed1980

Phosphoenolpyruvate-dependent glucose phosphotransferase activity in Streptococcus mitis ATCC 903.

A constitutive phosphoenolpyruvate (PEP)-dependent glucose phosphotransferase system was found in decryptified cells of Strep. mitis. The system displayed saturation kinetics and the apparent Km value for the non-fermentable analogue 2-deoxyglucose (2DG) was 0.4 mM. Sodium fluoride inhibited the activity when 2-phosphoglycerate was used as the energy source instead of PEP. Intact cells accumulated 2DG and also a derivative that behaved chromatographically like 2DG-6-phosphate. PEP-dependent glucose phosphotransferase activity was also demonstrated in freshly collected plaque.

Adult↗
PubMed1978

Isoelectric focusing studies on the beta-fructofuranosidases and alpha-glucosidases of Streptococcus mitis.

Extracts of Streptococcus mitis ATCC 903 were analysed for beta-fructofuranosidase and alpha-glucosidase activities by isoelectric focusing in thin-layer polyacrylamide gels combined with zymogram procedures. Three bands of activity were visualized in the gels after incubation with sucrose (pI 4.05, 4.25 and 4.85) and three other bands after incubation with p-nitrophenyl alpha-D-glucopyranoside (pI 3.90, 4.45 and 4.65). The enzymes responsible for the reaction with sucrose were identified as beta-fructofuranosidases (EC 3.2.1.26) for the following reasons: identical enzyme bands were visualized in the gels after incubation with raffinose; no enzyme bands appeared in the gel after incubation with the alpha-glucosides maltose, turanose, trehalose and melezitose; and the soluble fraction hydrolysed sucrose to equimolar amounts of glucose and fructose.

Glucosidases↗
PubMed1977

[Tissue compatibility of bone cement with and without barium sulfate (author's transl)].

Cylindrical plugs of polymerized Simplex-P bone cement with and without barium sulfate were implanted in the rabbit tibial metaphysis. Titanium was used as control material. The animals were observed for 4--4.5 months. Histological analysis showed that all titanium implants were healed into the bone with a direct bone-implant contact, which was also true for about 60% of the cement implants. The remaining cement implants were encapsulated by connective tissue, probably due to biomechanical factors. It was not possible in this study to show a difference in the tissue reaction to bone cement containing barium sulfate and bone cement free from barium sulfate.

Animals↗
PubMed1977

Reaction of bone to the acute chemical trauma of bone cement.

The acute chemical trauma of bone cement was investigated in the rabbit tibia. With the experimental model used, the surgical trauma and the thermal effects of the cement could be minimized. Each animal received one implant of polymerized cement as a control and one implant of polymerizing dough as the test material. The animals were observed for up to seventy days and the specimens were then studied by various techniques of histology, microangiography, fluorochrome labeling, and microradiography. With this experimental method the monomer trauma did not add to the minimized surgical trauma. Moreover, no detectable influence on bone regeneration was noted. In view of this minor effect, we suggest that the surgical preparation of the implant bed and the very procedure of inserting bone cement are more important for the acute tissue trauma than is monomer leakage alone.

Animals↗
PubMed1976

Autolysis in strains of viridans streptococci.

Seven strains of viridans streptococci of the species Streptococcus sanguis, S. mutans and S. mitis were investigated for autolysis. The effect of pH, salt concentration and temperature on the autolytic process was studied in Na2HPO4/NaH2PO4 buffer. Whole cells and walls of all strains autolysed most rapidly at pH values above 7. Autolysis of whole cells of S. sanguis and one strain of S. mitis (ATCC15909) was maximal in 0-05 TO 0-2 M buffer, while the two S. mutans strains and S. mitis ATCC15912 showed maximal autolysis in 0-5 and 1-0 M buffers. Cultures harvested in the stationary phase of growth possessed only slightly decreased autolytic activity compared with those from the exponential phase. Whole cells autolysed more rapidly at 37 degrees C Than at 45 degrees C and 10 degrees C. Autolysis of isolated walls of three strains of S. mitis (ATCC903, ATCC15909 and ATCC15912) was maximal at pH 7-0 AND 7-5 and in 1-0 M buffers. Streptococcus mitis ATCC15909 also showed maximal lysis in 0-01 M and 0-5 M buffers. An endopeptidase action of the autolytic system of S. mitis ATCC15912 was indicated by the progressive release of soluble amino groups during autolysis of the walls. No release of reducing groups was observed. Several free amino acids were released during autolysis of these walls, alanine, lysine and glutamic acid being in greatest quanitity.

Amino Acids↗
PubMed1976

Tissue reaction to methyl methacrylate monomer. A comparative study in the rabbit's ear on the toxicity of methyl methacrylate monomer of varying composition.

The aim of the present investigation was to evaluate if a bone cement monomer with a high concentration of accelerator (N,N-dimethyl-p-toluidine) is more toxic than a methyl methacrylate monomer, free from accelerator. 1) No difference in the acute local toxicity between CMW, Simplex-P and pure methyl methacrylate monomer was seen. 2) By gas chromatography. N,N-dimethyl-p-toluidine was shown to be water soluble to a small extent. Any bone cement monomer in current use can be fully dissolved in saline to a concentration of about 1 per cent.

Animals↗
PubMed1975

Incorporation of stainless steel, titanium and Vitallium in bone.

Operative trauma, implant instability and corrosion are recognized as aetiological factors in the production of the soft-tissue capsule often present round a metal implant in bone. In the present experimental study, the isolated effect of corrosion was evaluated under standardized experimental conditions when operative trauma was minimal and implant movement was negligible. The reaction of bone to stainless steel, titanium and Vitallium was studied by histological and biomechanical methods, and compared to that provoked by copper. No soft-tissue capsule was found round the modern materials, but copper gave rise to a marked tissue reaction. It is concluded that a traumatic operative techniques and implant immobility are more effective for stable incorporation of metallic implants in bone than the nature of the implant itself, provided that one of the modern, low-corrosive metals or alloys is used.

Angiography↗