Biomedical subjects
Publications and source records attributed to L Linder.
A method is described which permits study of the interface of tissue and bulk implant at the light and electron microscopic level. It is based on epoxy embedding of implant and surrounding tissue with subsequent separation of implant and plastic. The separation takes place at the interface between tissue and implant; neither cells nor matrix are disturbed.
Effective antihypertensive therapy has recently been shown to reduce not only the incidence of stroke, but also myocardial infarction irrespective of the drug(s) used. The well-documented preventive effect of beta-blockers in patients who suffered a myocardial infarction (secondary prevention) cannot be extended to patients with hypertension without overt coronary artery disease (primary prevention), except perhaps for non-smoking men. Despite strong experimental evidence, information on a possible secondary preventive effect of calcium antagonists in man is scant, and two double-blind placebo-controlled trials in secondary prevention with verapamil (320 mg) in a total of 1436 patients and nifedipine (30 mg) in 2279 patients did not reveal an overall treatment benefit. There are another six on-going trials. In the management of hypertension, large-scale trials may never help in selecting a particular drug for cardiac event reduction, and probably for many years the goals will be to normalize blood pressure with increased emphasis on the need to remedy other cardiovascular risk factors, in particular smoking.
The aim of this work was to study the influence of bacterial cell concentrations and inorganic anions on lysis of Streptococcus mutans BHT by human salivary lysozyme (HSL). HSL was partly purified from saliva by ion exchange chromatography. The bacteria were grown in a synthetic medium containing 3H-thymidine to monitor DNA release. The experiments demonstrated that release of 3H-thymidine was dependent on the bacterial cell concentration and an apparent Km-value corresponding to approximately 2.9 X 10(8) cells/ml was calculated. The influence of I-, Br-, Cl-, F-, HCO3- and SCN- on bacteriolysis was studied. All anions tested were slightly inhibitory on the action of HSL. The inhibition varied from 7 to 76% depending on the ion and ionic strength. The order of addition of HSL and sodium chloride caused different lytic responses. This was reflected by the amount of HSL adsorbed by the bacteria.
Streptococcus mitis ATCC 903 and Streptococcus sanguis 804 could utilize large peptides present in proteose peptone as their sole source of nitrogen but grew poorly in amino acid medium. By contrast, Streptococcus mutans BHT and S. mutans IB grew in amino acid medium but could not utilize large peptides. Streptococcus sp. strain Bravato had requirements for both peptides and amino acids. Peptide size did not seem important for the utilization of peptides by S. mitis except that dipeptides were not utilized. Large peptides were essential for depressed hyaluronidase synthesis in nongrowing S. mitis. Intracellular aminopeptidase activities were high in S. mitis ATCC 903 and Streptococcus sp. strain Bravato, intermediate in S. sanguis 804, and low in S. mutans BHT and S. mutans IB.
The tissue trauma caused by leakage of monomer from curing bone cement was studied in rabbit bone. With a chamber method it was possible to study by intravital microscopy the tissue response in the same animal from the time of cement application to as long as 350 days afterward. The immediate monomer effects were mainly vascular: blood flow disturbances, blood flow standstill, and intravascular hemolysis. The most striking finding was that the extent of vascular disturbance was related to the type of tissue afflicted: In fatty marrow the effects were widespread, and in bone or fibrous tissue they were very limited. This is interpreted to reflect the affinity of the monomer to lipid-rich tissues. Follow-up observations showed marked resorption of marrow fat cells during the first weeks after injury, whereas very little bone was resorbed.
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The aim of this work was to study the bacteriolytic ability of human salivary lysozyme (HSL) on Streptococcus mutans BHT. The cells were grown in a synthetic medium containing 3H-thymidine to monitor DNA release after incubation with either HSL, purified by ion exchange chromatography, or hen egg white lysozyme (HEWL). The experiments demonstrated that HSL as well as HEWL could liberate DNA from cells. The lysis was dependent on enzyme concentration as well as incubation-time. Approximately 80% of the 3H-thymidine was released at final concentrations of 4.5 micrograms/ml and incubation-times exceeding 16 hr. Additional treatment of the suspensions with DNase increased the levels of released radioisotopes. The lytic ability of HSL and HEWL was similar at low concentrations. HSL inactivated with goat antiserum to human lysozyme decreased the liberation of DNA by about 70%. This study suggests that HSL can lyse S. mutans BHT without presence of inorganic ions.
Cells of Streptococcus mitis ATCC 903 were converted to stable protoplasts by the cell wall-degrading M-1 enzyme of the mutanolysin complex isolated from Streptomyces globisporus. Over 90% of total glucokinase (EC 2.7.1.2), aminopeptidase (EC 3.4.11.1), and dextranglucosidase (EC 3.2.1.70) was recovered in the cytoplasmic fraction, whereas over 20% of total invertase (beta-fructofuranosidase: EC 3.2.1.26) was released during protoplast formation. ATPase (EC 3.6.1.3). chymotrypsin-like protease (EC 3.4.21.1), arginine aminopeptidase (EC 3.4.11.6), and lactate dehydrogenase (EC 1.1.1.27) were detected in Triton X-100 extracts of the cytoplasmic membrane fraction by crossed immunoelectrophoresis in combination with enzyme-staining procedures. By these methods, NADH dehydrogenase (EC 1.6.99.3), aminopeptidase, and lactate dehydrogenase were detected in the cytoplasmic fraction. Aminopeptidases in the cytoplasmic fraction differed from this activity in the membrane fractions in electrophoretic mobility and substrate specificity.
An extremely strong mechanical bond between cement and bone was observed in three patients with cemented hip protheses who underwent revision operations. The nature of the bone--cement attachment was studied by electron microscopy. The tissue at the interface was found to be made up of viable bone alternating with areas of soft tissue containing macrophages. The important qualitative differences between this reaction and the reaction seen around inert materials such as titanium are discussed.
Ten cylindrical implants, made of polycarbonate and covered with a 120-250-nm-thick layer of pure titanium, were implanted into each tibial metaphysis of five rabbits. Observation time was 12 weeks. The implants were surrounded by mature, living bone. No soft tissue intervened between bone and implant at any point. With TEM microscopy the titanium was shown to be bordered by a 20-nm-thick layer of proteoglycans, showing the characteristics of ground substance, and separating the collagen from the implant surface. Cells at the interface were likewise separated from the titanium by such a layer. Hydroxyapatite crystals were observed within the ground substance layer, occasionally seemingly in direct contact with the titanium. Normal mineralization was present 100-500 nm from the implant surface. While this study aims at defining interface anatomy, it also shows that macroscopically smooth-surfaced titanium can readily heal into bone without a soft tissue envelope. This could be of help for materials' choice and design of permanently fixed implants.
In 70 total hip arthroplasties exchanged because of mechanical loosening of the stem prosthesis, localized bone resorption or scalloping was found in 33 cases. In 19 of the 33 cases the process started at the level of the tip of the stem, which in 15 cases was found to be in direct contact with cortical bone as observed in the radiographs obtained immediately after the primary surgery. In 37 failures without scalloping this metal-to-bone contact was less common. It is concluded that localized bone resorption may occur as a result of mechanical stress and in the absence of deep infection. It is also suggested that the phenomenon might be avoided by proper cementing technique and centering of the tip of the stem, perhaps with the help of a centering device.
Twenty-one total hip arthroplasties were revised because of aseptic loosening. The bone and soft tissue membrane bordering the cement in a total of 37 biopsies from the acetabulum and femur were studied histologically and by enzyme histochemistry. The soft tissue membrane was infiltrated with macrophages and had high acid phosphatase activity. Other inflammatory cells were rare or absent. Concomitant bone formation and bone resorption were usually present at the bone-soft tissue border. The bone generally consisted of viable, remodeled lamellar bone. The host bone seemed to have been resorbed by a soft tissue front moving outward from the cement. Reactive new bone formation began at the bone-soft tissue border and appeared to constrain the resorptive process. Articular wear seemed to play no part in initiating the loosening process. The role of bone cement in this respect is obscure, because there were no obvious local signs of cytotoxicity. These observations support the theory of mechanical instability as the primary cause of the tissue reaction.
The action and interaction of topical 2% epinephrine hydrochloride and 0.5% timolol maleate therapy were studied in 12 normal and 16 ocular hypertensive subjects. Measurements of intraocular pressure, outflow facility, and aqueous secretion by fluorophotometry were made. Uveoscleral outflow values were calculated. Epinephrine, applied topically twice daily for one week, resulted in a decrease in IOP of 3.3 +/- 0.9 mm Hg and an increase in outflow facility of 0.05 +/- 0.01 microL/min/mm Hg, as well as an increase in the rate of aqueous production of 0.32 +/- 0.09 microL/min. Uveoscleral outflow showed an increase of 0.83 +/- 0.23 microL/min. Timolol, applied topically twice daily for one week, reduced the IOP 3.9 +/- 1.0 mm Hg and decreased aqueous flow 0.84 +/- 0.23 microL/min, but produced no change in outflow facility or uveoscleral flow. When epinephrine and timolol are given in combination, the effects in lowering IOP may not be completely additive.
Using a vital microscopic method, it has been possible to follow the vascular changes and bone remodelling in the same bone graft from the time of transplantation till one year afterwards. Grafts which received their first vessel early (5-9 days after grafting) contained vital bone and a vivid blood circulation one year after transplantation. Grafts which received their first vessel late (17-29 days after grafting) were only partly revascularized after one year and contained islands of dead bone. Minimal surgical trauma to both graft and the host bed is important for early revascularization of the graft, and, therefore, also contributes to a more complete incorporation of the graft.
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A screw-shaped titanium chamber has been designed for serial in vivo observations of the bone-implant interface. First, the chamber is implanted; later a test substance, e.g. bone cement, is inserted in the chamber and brought in contact with the bone with minimal trauma. Both acute and long-term effects can be intravitally observed, photographed, and recorded.
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