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Biomedical subjects

K H Schmidt

Publications and source records attributed to K H Schmidt.

At least 91 records · Page 5Linked to original sources
PubMed1988

Examination of new bone growth on aluminium oxide implant contact surfaces after oral administration of ossein-hydroxyapatite compound to rats.

In view of the many disadvantages of transplantation of autologous bone tissue, factors must be found which locally and systemically will adjust the balance between bone resorption and deposition in favour of new bone growth. The present study was undertaken, therefore, to examine whether oral administration of ossein-hydroxyapatite compound (OHC) could stimulate new bone growth on aluminium oxide implant surfaces and, if so, whether it was the mineral or organic part of the compound which was responsible. Whilst under anaesthesia, adult male Wistar rats each had 2 holes drilled into the femur and 2 precisely fitting aluminium oxide implants inserted. The animals were divided into 5 groups each of 5 rats and the groups received oral daily doses of 20 mg OHC, 100 mg OHC, 10 mg hydroxyapatite, 50 mg hydroxyapatite or no supplement (controls), respectively. After 20 days, each implant was evaluated by 5 cuts through the marrow area and the thickness of the newly grown layer of bone measured by a morphometric procedure. The results showed a significant increase in new bone growth for the 100 mg OHC group in comparison to the control group, and in comparison to the hydroxyapatite group. Because both supplemented groups received equivalent dosages of calcium and phosphate, the additional stimulation of new bone growth must have been due to the organic part of OHC (ossein). It is suggested that these results should stimulate in particular the clinical use of OHC in the critical initial phase of implant healing and delayed fracture healing.(ABSTRACT TRUNCATED AT 250 WORDS)

Aluminum↗
PubMed1988

[Segmentation of MR tomograms for quantitative volume estimation].

MR tomography yields better contrasts for soft tissues than other imaging methods. This allows a reliable measurement of the volume of brain structures, in particular for the ventricular system and e. g. structures in hydrocephalic states. Therefore a method is proposed for segmentation and volume estimation of MR tomograms that is implemented via a computer program. This method provides an accurate determination of the volume tested on multiple-slice-images of normal patients and a phantom. The substantial features and possibilities of this program usable for all kinds of structures in MR-tomograms are explained here in detail.

Cerebral Ventricles↗
PubMed1988

On the nature of IgG dimers. I. Dimers in human polyclonal IgG preparations: kinetic studies.

Human polyclonal IgG for therapeutic or prophylactic purposes is usually prepared from pooled plasmas taken from more than 1000 donors. After storage in solution under physiological conditions for a sufficiently long period, a considerable percentage of dimers (approx. 10-30% [w/w] at a protein concentration of approx. 160 mg/ml) represents the main component of aggregates in contrast to the essentially monomeric IgGs of monoclonal or single donor origin. Analysing the kinetics of monomer-dimer equilibration suggests assuming approx. 10(6) different antibody (ab) populations interacting independently and simultaneously with a specific partner of the reaction. Concerning the average apparent (functional) equilibrium constant of association, Kapp., a distinction could be made between two main populations characterized by values in the range if approx. 2.5-3.0 X 10(10) M-1 and 1.0 X 10(12) M-1, respectively. The results were obtained by computer simulation, taking an association rate constant, k+1, of 5 X 10(5) M-1 s-1 as a basis. Since the main part of the individual populations was found to interact Fc-independently via Fab-located binding sites, we suppose that the dimers are for the most part complexes of idiotypic (Ids) and anti-idiotypic abs (anti-Ids). Moreover, dimerization seems to be mainly a bivalent binding reaction, at least at the experimental concentrations. The results are in line with the concept of an idiotypic network regulation in man.

Animals↗
PubMed1988

On the nature of IgG dimers. II. Idiotype--anti-idiotype complexes of polyclonal and monoclonal origin: size distribution patterns and molecular geometries.

Electron micrographs of a fraction containing dimers isolated from pooled human polyclonal immunoglobulin G (IgG) suggest essentially a cyclic geometry compatible with bivalently associated monomers. It is obvious that such a structure can be produced by idiotype (Id)--anti-idiotype (anti-Id) interactions where the latter are able to neutralize certain combining site related Id functions. Accordingly, antibody (ab) activities against tetanus toxoid (tt) and rubella antigen (ag) were found to be almost exclusively confined to the monomeric molecules in preparations composed of monomers and dimers only. Moreover, electron micrographs of complexes prepared from a murine monoclonal Id as well as anti-Id reveal the presence of ring complexes, especially of cyclic tetramers. Gel filtration patterns of mixtures containing equimolar concentrations (concns) of such abs (1.6 x 10(-6) M) show, correspondingly for 9 different Id--anti-Id pairs and therefore probably representing a more common feature, mainly the formation of even-numbered complexes, especially tetramers. That is basically in accordance to an equilibrium model developed by Archer and Krakauer but not from a quantitative point of view because non-ideality terms had not been originally included. Despite taking strain energies determined by Schumaker et al. for cyclic complexes of polyclonal rabbit abs and a bivalent hapten into account for computation of size distribution patterns, the predominant formation of dimers was, nevertheless, again predicted by the modified theory in contrast to the experimental results. Fundamental conformity could only be achieved by further decreasing one of the statistical factors, namely the ring closing factor, which theoretically influences the generation of cyclic dimers. Therefore, referring to the experimental results of Schumaker et al., we postulate a strain energy well above 700 cal/mol for cyclic dimers produced by interacting Ids and anti-Ids. In general, the findings confirm predictions based on the interpretation of recent kinetic studies.

Animals↗
PubMed1987

Binding of fibrinogen fragment D to group A streptococci causes strain dependent decrease in cell surface hydrophobicity as measured by the salt aggregation test (SAT) and cell clumping in polyethylene glycol.

Group A streptococcal reference strains of various M-types as well as three clinical isolates, and clinical isolates of group B, C and G streptococci were compared with respect to their agglutination by fibrinogen, specific binding of monovalent fibrinogen fragment D, and their hydrophobicity measured by salt aggregation in ammonium sulfate dilutions (SAT). Fibrinogen fragment D binding to M positive group A streptococci and clinical isolates of group A reduced salt aggregation of these strains from 0.06 molar to 2 molar in the ammonium sulfate dilution series. Group A, M protein negative and group B, C and G control strains used aggregated only at high ammonium sulfate concentration (2 molar) or not at all. Treatment of these strains with fibrinogen fragments did not influence their weak salt aggregation. By elution of specific retained fragment D from the type 1 M positive strain 40/58II by treatment of cells with 0.1 molar citric acid, 6 molar urea, buffer, pH 3.0, surface hydrophobicity could partially be restored (SAT titer 0.5 molar). Treatment of streptococcal cells with fibronectin or albumin at much higher protein concentrations had a moderate effect on surface hydrophobicity. These results indicate that binding of fibrinogen fragment D to the receptor can block a hydrophobic surface domain of the receptor or induce a sterical hindrance affecting surface exposure of associated surface molecules. A fibrinogen receptor-also responsible for binding of fibrinogen fragment D-is in M positive group A streptococci covalently linked to M protein. Decrease of salt aggregation tendency after mild pepsin treatment to release M protein supported these findings.

Agglutination↗
PubMed1987

A screening of streptococci freshly isolated from human and animal sources for binding of human IgG.

Human isolates of groups A, C and G streptococci as well as animal isolates of group C were investigated with respect to their binding capacity for human IgG by using the direct fluorescence technique and the Mancini test. From each serological group of human isolates, more than 100 strains were tested. The results were evaluated statistically with respect to serological group, type and source of isolates. Between human isolates of groups A, C and G, no statistical differences concerning IgG binding were found. However, group C streptococci isolated from pigs showed a significantly higher number of strains with high IgG binding than the human isolates of groups A, C and G. Group A streptococci isolated from suppurating lesions showed an increased IgG uptake when compared with isolates from scarlet fever patients or patients with throat infections. However, strong IgG binding by group A streptococci seems not to be restricted to certain types. By using selected streptococcal strains, it was found that IgG absorption from a solution of purified IgG was much higher than from IgG solutions containing albumin or from diluted serum. The results are discussed in connection with the competition of different plasma proteins for binding sites on the streptococcal cell surface and with a possible influence of IgG receptors on the virulence of streptococci.

Animals↗
PubMed1987

Extraction of group C streptococcal IgG-binding receptor and characterization of the active peptides by Western blotting and isoelectric focusing.

Three different enzymatic extraction procedures were tested for their effectivity in releasing IgG-binding peptides from the streptococcal cell wall. Streptococcus equisimilis strain 12628 isolated from pig was incubated with phage-associated lysin, trypsin and Streptomyces globisporus lytic enzyme and the extracts were investigated by Western blotting, indirect erythrocyte agglutination and Ouchterlony diffusion for IgG-binding activity. With all treatments IgG-binding peptides were extracted. However, no homogenous IgG-binding material was released by the enzymes tested. In each case a multiple peptide pattern with IgG-binding activity was found. The molecular weights of the active peptides released also differed between the extraction procedures. The isoelectric points between 4.0 and 4.3 of IgG-binding components were found to be similar for all three extracts.

Animals↗
PubMed1986

Structural changes in membranes of large unilamellar vesicles after binding of sodium cholate.

The interaction of the bile salt cholate with unilamellar vesicles was studied. At low cholate content, equilibrium binding measurements with egg yolk lecithin membranes suggest that cholate binds to the outer vesicle leaflet. At increasing concentrations, further bile salt binding to the membrane is hampered. Before the onset of membrane solubilization, diphenylhexatriene fluorescence anisotropy decreases to a shallow minimum. It then increases to the initial value in the cholate concentration range of membrane solubilization. At still higher cholate concentrations, a drop in fluorescence anisotropy indicates the transformation of mixed disk micelles into spherical micelles. Perturbation of the vesicle membranes at molar ratios of bound cholate/lecithin exceeding 0.15 leads to a transient release of oligosaccharides from intravesicular space. The cholate concentrations required to induce the release depend on the size of the entrapped sugars. Cholesterol stabilizes the membrane, whereas, in spite of enhanced membrane order, sphingomyelin destabilizes the membrane against cholate. Freeze-fracture electron microscopy and phosphorus-31 nuclear magnetic resonance (31P NMR) also reflect a change in membrane structure at maximal cholate binding to the vesicles. In 31P NMR spectra, superimposed on the anisotropic line typically found in phospholipid bilayers, an isotropic peak was found. This signal is most probably due to the formation of smaller vesicles after addition of cholate. The results were discussed with respect to bile salt/membrane interactions in the liver cell. It is concluded that vesicular bile salt transport in the cytoplasm is unlikely and that cholate binding is restricted to the outer leaflet of the canalicular part of the plasma membrane.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1986

Changes in the cellular immune response by a subfraction of burned murine skin.

Sepsis due to impaired host defence mechanisms is one of the most frequent causes of death in severely burned patients. However, it is not precisely known to what extent syntheses and release of suppressive mediators of the burned tissue affect the cellular and humoral immune responses. In this study a decreased production of plasminogen activator by macrophages is demonstrated after incubation with skin components, indicating a decreased macrophage helper function for T-B cell cooperation. An additional effect of the skin fraction is a considerable increase in mitogenic activity as measured in the antibody-forming cell test. This enhancement of macrophage-T-B cell cooperation is concentration dependent and lower in the burned skin fraction as compared to the unburned control. A known skin-derived cytokine with mitogenic properties is epidermal cell-derived thymocyte activating factor (ETAF) exhibiting interleukin-1 (I1-1) like activity including mitogenic enhancement of murine thymocyte stimulation by phytohaemagglutinin. Burned and control skin fraction as tested in a thymocyte assay did not show interleukin-1-like activity. The experiments suggest the presence of a skin-derived growth factor which is not interleukin-1 but which stimulates T-B cell cooperation when there is depression of macrophage function. Further purification is required in order to assess the clinical relevance of the factor in burned patients.

Animals↗
PubMed1986

Albumin bound to the surface of M protein-positive streptococci increased their phagocytosis by human polymorphonuclear leukocytes in the absence of complement and bactericidal antibodies.

Using a phagocytosis assay (Leijh 1980, Infect. Immun. 30, 421), determination of chemiluminescence, and transmission electron microscopy, the influence of the binding of albumin to M protein-positive group A streptococci on their phagocytosis by human polymorphonuclear leukocytes (PMNL) was investigated. Coating of streptococci with albumin in the absence of other serum components enhanced phagocytosis but not killing of the bacteria. Complement had no additional effect on engulfment. Fibrinogen reduced the enhancing effect of albumin. Albumin had no additional effect on the high phagocytosis rate of an M-protein-negative strain. It could be demonstrated that human PMNL bound human serum albumin-gold conjugate. The results are discussed with regard to the role of plasma proteins in the phagocytosis of streptococci under in vivo-conditions.

Antibodies, Bacterial↗
PubMed1986

Semi-quantitative determination of IgG-binding structures on bacteria by direct fluorescence technique.

A simple semiquantitative method for determination of IgG-binding structures on bacteria by direct fluorescence technique is described. The fluorescence of bacterial bound IgG-FITC-conjugate was measured in a paste-like bacterial sediment by using a fluorescence microscope photometer unit. For this purpose sharply centrifuged IgG-FITC conjugate treated bacteria, from which the washing fluid was carefully removed, were transferred to a glass slide and fluorescence was measured at the contact layer of the adhered drop on the inverted slide. The measured fluorescence intensity area was found to be correlated with the amount of bound IgG-FITC/cell, if bacteria had been incubated with an excess of fluorescein labeled IgG. The IgG-binding of different streptococcal strains was compared with the average IgG-binding of strain Cowan I resulting from 13 different cultivations. For strain Cowan I 9.4 X 10(4) IgG-molecules were estimated to bind on one staphylococcal cell. For a screening of IgG-binding bacterial strains the method did not demand a standardization of bacteria by cell counting.

Cell Membrane↗
PubMed1986

Effect of functional stimulation on ascorbate content in phagocytes under physiological and pathological conditions.

Neutrophil polymorphonuclear leucocytes and macrophages contain 10-40 times increased intracellular ascorbate concentrations compared to plasma. A slight decrease of ascorbate content could be observed in total white blood cells and in monocytes upon stimulation with opsonized zymosan. These decreases were more pronounced in peritoneal and alveolar macrophages from rats. In patients with rheumatoid disease whose phagocytes are exposed to a constant challenge, significantly lowered intracellular ascorbate contents were found in neutrophils and mononuclear cells. Surgical and thermal trauma in rats depressed intracellular ascorbate levels in peritoneal macrophages. These results are indicative of an essential role ascorbic acid plays in phagocytic cells.

Animals↗
PubMed1985

Experimental and preliminary clinical experience with absorbable calcium phosphate granules containing an antibiotic or antiseptic for the local treatment of osteomyelitis.

Experimental studies on dogs with staphylococcal osteomyelitis showed that it is possible to reduce florid bone suppuration by the use of hydroxyapatite granules containing an antibiotic or antiseptic. In our series the use of flucloxacillin hydroxyapatite granules was superior to other treatment methods. Twelve patients were treated with thorough sequestrectomy, reliable wound closure and suitable stabilization supplemented with an implant of antibiotic or antiseptic hydroxyapatite granules, and an autologous spongiosa graft for large bone cavities or for discontinuity between the bone ends. The results of this preliminary study showed the treatment to be effective.

Adolescent↗
PubMed1985

[MR of the knee joint. Imaging of the normal anatomy and pathological findings using surface coils].

A special surface coil was developed with the intention of producing optimal resolution and signal-to-noise ratio for the examination of the knee joint by MRI. Eight volunteers and 25 patients with various abnormalities of the knee have been examined. Normal anatomical structures can be differentiated and there is high diagnostic reliability for lesions of the meniscus, as confirmed by arthroscopy and surgery. Cartilage lesions are less well demonstrated. Total rupture of cruciate ligaments is clearly shown, but partial rupture can often be recognised on the basis of indirect signs only. Good diagnostic results were obtained in cases of osteochondritis dissecans and chondropathia of the patella.

Adolescent↗
PubMed1985

[Cryosurgery in inoperable rectal cancer].

26 patients suffering from nonresectable adeno-carcinoma of the rectum have been treated since Sept. 1980. The mean age was 72 years. The temperature of the probe tip was -160 degrees C. A closed system with liquid nitrogen was used. In 12 patients there was an indication of systemic inoperability, 13 had an irremovable tumour or metastases. 1 patient refused curative operation. Cryosurgery was aimed at reducing the mass of rectal tumours and preventing colostomy. Colostomy could also be avoided in 12 of 14 patients suffering from stenosing tumours. The advantages of cryotherapy are outpatient treatment, no anaesthesia and minimal complications. Generally, this method will yield good results in palliative treatment of inoperable rectal carcinomata.

Adenocarcinoma↗
PubMed1984

[Secondary immunodeficiencies following severe skin burns].

Despite of modern fluid resuscitation, electrolyte management and respiratory care techniques 70% of severely burned patients often survive the early posttraumatic phase only to later succumb to septic complications. Acquired deficiencies in host defense mechanisms are largely held responsible for this increase in susceptibility to sepsis. The thermal insult affects the complex interactions of cells of the immune system by generation and release of suppressive mediators which, in turn, either cause defective cellular functions or overstimulation of regulatory pathways of host defense.

Burns↗
PubMed1984

Quantitative differences in specific binding of fibrinogen fragment D by M-positive and M-negative group-A streptococci.

Selected M-positive and M-negative group-A streptococcal strains were investigated with respect to their selective absorption of plasmin fibrinogen degradation products (FDP) in a simple batch technique. After incubation of killed streptococci with the FDP mixture, the centrifuged supernatants were investigated by SDS-electrophoresis and the binding capacity of the strains was calculated by evaluation of the scanning curves of stained gels. It was found that there is a specific uptake of the C-terminal fragment D by both M-positive and M-negative strains. Although the M-positive strains bound more fragment D (30%-80%) than did the M-negative strains (10%-15%), it could be clearly shown that the loss of M-protein was not necessarily linked with a total disappearance of fibrinogen binding activity. Fragment D blocked the agglutination of streptococci by fibrinogen. Washing the streptococci preincubated with FDP with a 0.1 M citric acid, 6 M urea buffer, pH 3.0, restored agglutination. Treatment of FDP-incubated bacteria with this buffer was found to be a means of recovering pure fragment D from streptococcal cells. It is suggested that M-positive and M-negative streptococci have qualitatively similar binding sites. These receptors might be reduced in the M-negative streptococci. Human serum albumin and Tween 20 did not influence the interaction between streptococcus and fibrinogen.

Agglutination↗