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Biomedical subjects

U Gross

Publications and source records attributed to U Gross.

At least 163 records · Page 9Linked to original sources
PubMed1990

The effect of glass-ceramic implants on matrix vesicle calcification after two weeks of rat tibial bone healing.

Type, size and distribution of extracellular matrix vesicles (MV), known mediators of primary calcification, were studied around bone-bonding and metal-oxide containing, nonbonding, glass-ceramic implants. This was performed in order to further understand the different effects of implants on bone healing. At 14 days after implantation in adult rat tibial bone the effects of different implants on MV were studied by transmission electron microscopy and computerized morphometry. A total number of 4607 MV in 245 electron micrographs were counted and grouped according to diameter, distance from the calcifying front, and classified as four types: "empty," "amorphous," "crystal," and "rupture." The sequence of types according to diameter and distance was recorded as follows around both implants tested: "rupture" MV were the closest to the front with the largest diameter, followed by "crystal," "amorphous," and "empty," MV with the largest distance from the front and the smallest diameter. Most vesicles were concentrated in a distance of less than 2.4 microns from the front and between diameters of 0.06 microns and 0.22 microns. The noncalcified extracellular matrix around bone-bonding implants contained more MV than the matrix around the nonbonding type (26.24 MV/10 microns2 and 18.76 MV/10 microns2). MV distribution according to types showed that around bonding implants there was a higher percentage of "crystal" and a lower percentage of "rupture" when compared to the nonbonding type. These results indicate that bonding implants affect osteoblastic function by increasing the vesicular number and retardation of intravesicular crystal formation. It might be suggested that bonding implants induce an increase in the process of primary calcification and a decreased rate of crystal formation resulting with the highest organization of the healing bone.

Animals↗
PubMed1990

SEM study of surface alterations of bioactive glasses and glass--ceramics in a bony implantation bed.

Back scattered electron (BSE) images of glasses and glass-ceramics with different degrees of bone-bonding behaviour have been investigated. After the implantation of probes in the femur of rats changes of the surface material, induced by leaching and corrosion (material response) and of the tissue in the drill hole (host response), were studied. The results demonstrate advantages of using BSE images and give further information for understanding the sequential changes in the implant material which occur mainly in bone-bonding materials. The density of the leached zone was not homogeneous and it therefore might be possible that preferential leaching of the glass matrix contributes to the mineralization of extracellular matrix. These findings could be of use for further development of surface reactive materials.

Animals↗
PubMed1990

The relationships between selected anthropometric and socio-economic data in schoolchildren from different social strata in Rio de Janeiro, Brazil.

The nutritional status according to anthropometric data was assessed in 756 schoolchildren from 5 low-income state schools and in one private school in the same part of Rio de Janeiro, Brazil. The prevalence of stunting and wasting (cut-off point: less than 90% ht/age and less than 80% wt/ht) ranged in the public schools from 6.2 to 15.2% and 3.3 to 24.0%, respectively, whereas the figures for the private school were 2.3 and 3.5%, respectively. Much more obesity was found in the private school (18.0%) than in the state schools (0.8-6.2%). Nutritional problems seem to develop more severely in accordance with the increasing age of the children. Therefore it appears advisable to assess schoolchildren within the context of nutritional surveillance system.

Adolescent↗
PubMed1990

A ribosomal protein of Yersinia pseudotuberculosis having partial epitope identity with HLA-B27.

The phenotype HLA-B27 is common in patients who develop reactive arthritis after having an infection. One hypothesis concerning the pathogenesis of reactive arthritis is that molecular mimicry between HLA-B27 and certain bacterial components might be involved. It is known that an infection with Yersinia is commonly associated with reactive arthritis in B27 positive patients. Therefore, we were interested to investigate whether cross-reactivity between Yersinia and HLA-B27 exists. A gene library of Yersinia pseudotuberculosis was created in the plasmid vector pUC13. One of the resulting clones contained a gene encoding an intracytoplasmic protein that seems to have partial epitope identity with HLA-B27. It reacted in western blot. ELISA and immunoprecipitation with three different HLA-B27 specific monoclonal and polyclonal antibodies of the IgG and IgM class. However DNA-sequencing of the cloned Yersinia gene and the predicted amino acid sequence revealed only a very remote similarity with HLA-B27 in the primary structure. Instead, an extremely high degree of similarity with the ribosomal protein L4 of the S10 operon of Escherichia coli was identified indicating that the protein encoded by the cloned Y. pseudotuberculosis gene is a corresponding ribosomal protein.

Amino Acid Sequence↗
PubMed1990

Incorporation and degradation of hydroxyapatite implants of different surface roughness and surface structure in bone.

The interface of dense hydroxyapatite (HA) implants with different surface roughness was investigated after implantation into the spongy bone of the distal femur of rabbits by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) following transverse fractures in the interface. Each implant displayed considerable changes in surface morphology caused by leaching (increasing pore diameter), corrosion (particulate disintegration), and active resorption by osteoclasts. Macrophages were involved in "cleaning" the surface via phagocytosis of loose implant particles. Newly formed surface elevations provided adhesion points for fibers and fibrils. Subsequent mineralization of these areas stabilized the interdigitation of surface elevations and extracellular matrix with adhering fibers and contributed to the tensile strength in the interface. This investigation provides further knowledge about HA implants, which seem to be partially resorbed by osteoclast-like cells.

Animals↗
PubMed1989

Effect of glass-ceramic implants on primary calcification in rat tibial bone after injury.

Using histomorphometry and transmission electron microscopy the distribution of extracellular matrix vesicles around bone-bonding and non-bonding glass-ceramic implants in tibial bone healing was studied. Grouping of vesicles was performed according to type, diameter and distance to the calcified front. Most vesicles were 0.06-0.22 microns in diameter in both implants tested. The mean vesicular distance of matrix vesicles to the calcified front was statistically significantly lower in non-bonding material compared with KG Cera. The sequence of vesicle arrangement according to diameter was: 'empty', 'amorphous', 'crystal', 'rupture'. Empty vesicles were the smallest and rupture vesicles the largest. Distances of vesicles to the calcified front showed the same sequence of arrangement, while the rupture type was located nearest to the front. The findings support the widely acknowledged hypothesis on the role of matrix vesicles in mineralization. It was shown that mineralizing tissue around bone-bonding glass-ceramics contains more matrix vesicles, which are distributed further from the front with a lower degree of calcification. The parameters studied could serve as standard criteria for the evaluation of implant materials.

Animals↗
PubMed1988

The effect of glass-ceramic bone implant materials on the in vitro formation of hydroxyapatite.

The extracts of four glass-ceramic bone implant materials were investigated for dissolved material, for effects on in vitro formation of hydroxyapatite, and for surface morphology of glass-ceramic particles in scanning electron microscopy. In vitro leaching released substances that affected in vitro formation of hydroxyapatite, i.e., initiation time and growth of crystals. Leaching also changed the surface morphology of the materials. The ability of the materials to bond to bone did not correlate with the inhibition of hydroxyapatite formation by the released substances. Surface morphology and other factors at present not yet known are probably involved in controlling the bonding to bone of these ceramics.

Bone and Bones↗
PubMed1987

[Are stomach polyps an indicator of colonic carcinoma and colonic polyps an indicator of stomach carcinoma?].

Over a period of six years a total of 407 patients with polyps of the gastrointestinal tract were examined by gastroscopy and coloscopy and the findings analysed retrospectively. Among patients with colon polyps 10.5% were found also to have polypoid gastric lesions, among those with adenoma of the colon the prevalence was 11.7%. Only 2.4% of simultaneously diagnosed gastric lesions were found to be malignant or premalignant, a figure similar to the population average. But in patients with more than ten polyps of the colon both the prevalence of polypoid gastric changes and the significance of polyps with respect to precancerous lesions were clearly increased. On the other hand, in patients with epithelial polyps and/or glandular cysts colon polyps were found in 45%, in 42% with precancerous changes (adenoma). Thus patients with epithelial gastric polyps and glandular cysts probably constitute a group with a real additional risk of colon carcinoma. Regular coloscopy will thus reveal precancerous changes (adenoma) in the colon of 42% of such patients; coloscopic polypectomy will be an effective prophylactic measure against carcinoma of the colon.

Adenomatous Polyposis Coli↗