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Petra Johansson

Publications and source records attributed to Petra Johansson.

6 recordsLinked to original sources
PubMed2006

Retrieved implants from irradiated sites in humans: a histologic/histomorphometric investigation of oral and craniofacial implants.

PURPOSE: The aim of this report was to quantitatively and qualitatively evaluate the tissue response to bone-anchored implants retrieved from irradiated sites in patients. MATERIALS AND METHODS: The material consists of 23 consecutively received Brånemark implants (Nobel Biocare AB, Göteborg, Sweden) placed in pre- or postoperatively irradiated sites. Twenty-two of the 23 implants were suitable for histologic evaluation of undecalcified sections in the light microscope. RESULTS: The oral implants with shorter time in situ demonstrated sparse bone to implant contact with mainly dense connective tissue in the interface. However, for implants with longer time in situ, high amounts of bone-implant contact and bone fill of threads were noted. The mean values of bone-implant contact and bone area within the thread were calculated to 40% (16-94) and 70% (13-96), respectively. The craniofacial implants, with the exception of two implants lined with a capsular formation, demonstrated mature and newly formed bone at the bone-implant interface. The mean value for bone-metal contact was calculated to 45 and 53% for two specimens. The mean value for bone area within the thread ranged from 65 to 88% for three specimens. CONCLUSION; The possibility to achieve bone anchorage of implants in irradiated tissue was supported by the findings in this study. However, due to limited material, conclusions with regard to radiation dose and bone tissue response to implants cannot be stated.

Aged↗
PubMed2006

Histologic evaluation of Brånemark clinic oral implants retrieved from grafted sites.

PURPOSE: The aim of this report is to quantitatively and qualitatively describe the bone tissue response to Brånemark implants retrieved from grafted sites in patients. MATERIALS AND METHOD: The material consists of consecutively received Brånemark implants retrieved from grafted sites. Thirty-five of these implants, retrieved from 16 patients, were suitable for the histologic evaluation of undecalcified sections in the light microscope. RESULTS: The unloaded implants were mainly lined with soft tissue, and sparse bone-implant contact was observed only in some sections. The loaded implants, with the exception of one implant removed due to mobility, had mature and new bone-implant contact. Resorption of graft through cutting cone structures was detected. Cement lines were found separating bone-like tissue albeit no cellular content and bone tissue with detectable osteocytes. CONCLUSION: In this heterogeneous group of implants from grafted sites, the unloaded implants showed limited bone-implant contact. The autografts showed seemingly mixed viability as judged by the cell content in the osteocyte lacunae and cement lines separating areas with filled and empty lacunae.

Bone Transplantation↗
PubMed2005

The temperature dependence and involvement of mitochondria permeability transition and caspase activation in damage to organotypic hippocampal slices following in vitro ischemia.

The aggravating effect of hyperglycemia on ischemic brain injury can be mimicked in a model of in vitro ischemia (IVI) using murine hippocampal slice cultures. Using this model, we found that the damage in the CA1 region following IVI in the absence or presence of 40 mm glucose (hyperglycemia) is highly temperature dependent. Decreasing the temperature from 35 to 31 degrees C during IVI prevented cell death, whereas increasing the temperature by 2 degrees C markedly aggravated damage. As blockade of the mitochondrial permeability transition (MPT) is equally effective as hypothermia in preventing ischemic cell death in vivo, we investigated whether inhibition of MPT or of caspases was protective following IVI. In the absence of glucose, the MPT blockers cyclosporin A and MeIle4-CsA but not the immunosuppressive compound FK506 diminished cell death. In contrast, following hyperglycemic IVI, MPT blockade was ineffective. Also, the pan-caspase inhibitor Boc-Asp(OMe)fluoromethyl ketone did not decrease cell death in the CA1 region following IVI or hyperglycemic IVI. We conclude that cell death in the CA1 region of organotypic murine hippocampal slices following IVI is highly temperature dependent and involves MPT. In contrast, cell death following hyperglycemic IVI, although completely prevented by hypothermia, is not mediated by mechanisms that involve MPT or caspase activation.

Analysis of Variance↗
PubMed2005

Interaction of Helicobacter pylori with sialylated carbohydrates: the dependence on different parts of the binding trisaccharide Neu5Ac{alpha}3Gal{beta}4GlcNAc.

We have recently shown that binding of Helicobacter pylori to sialylated carbohydrates is dependent on the presence of the carboxyl group and the glycerol chain of Neu5Ac. In this work we investigated the importance of GlcNAc in the binding trisaccharide Neu5Acalpha3Galbeta4GlcNAc and the role of the N-acetamido groups of both Neu5Ac and GlcNAc. An important part of the project was epitope dissection, that is chemical derivatizations of the active carbohydrate followed by binding studies. In addition we used a panel of various unmodified carbohydrate structures in the form of free oligosaccharides or glycolipids. These were tested for binding by hemagglutination inhibition assay, TLC overlay tests, and a new quantitative approach using radiolabeled neoglycoproteins. The studies showed that the N-acetamido group of Neu5Ac is important for binding by H. pylori, whereas the same group of GlcNAc is not. In addition, Fuc attached to GlcNAc, as tested with sialyl-Lewis x, did not affect the binding. Free Neu5Ac was inactive as inhibitor, and Neu5Acalpha3Gal turned out to be active. The binding preference for neolacto structures was confirmed, although one strain also was inhibited by lacto chains. The combined results revealed that an intact Neu5Ac is crucial for the interactions with H. pylori. Parts of Gal also seem to be necessary, whereas the role of the GlcNAc is secondary. GlcNAc does influence binding, however, primarily serving as a guiding carrier for the binding epitope rather than being a part of the binding structure.

Carbohydrate Metabolism↗
PubMed2003

Studies on gangliosides with affinity for Helicobacter pylori: binding to natural and chemically modified structures.

Helicobacter pylori, like many other microbes, has the ability to bind to carbohydrate epitopes. Several sugar sequences have been reported as active for the bacterium, including some neutral, sulfated, and sialylated structures. We investigated structural requirements for the sialic acid-dependent binding using a number of natural and chemically modified gangliosides. We have chosen for derivatization studies two kinds of binding-active glycolipids, the simple ganglioside S-3PG (Neu5Ac alpha 3Gal beta 4GlcNAc beta 3Gal beta 4Glc beta 1Cer, sialylparagloboside) and branched polyglycosylceramides (PGCs) of human origin. The modifications included oxidation of the sialic acid glycerol chain, reduction of the carboxyl group, amidation of the carboxyl group, and lactonization. Binding experiments confirmed a preference of H. pylori for 3-linked sialic acid and penultimate 4-linked galactose. As expected, neolacto gangliosides (with Gal beta 4GlcNAc in the core structure) were active in our assays, whereas gangliosides with lacto (Gal beta 3GlcNAc) and ganglio (Gal beta 3GalNAc) carbohydrate chains were not. Negative binding results were also obtained for disialylparagloboside (with terminal NeuAc alpha 8NeuAc) and NeuAc alpha 6-containing glycolipids. Chemical studies revealed dependence of the binding on Neu5Ac and its glycerol and carboxyl side chains. Most of the derivatizations performed on these groups abolished the binding; however, some of the amide forms turned out to be active, and one of them (octadecylamide) was found to be an excellent binder. The combined data from molecular dynamics simulations indicate that the binding-active configuration of the terminal disaccharide of S-3PG is with the sialic acid in the anticlinal conformation, whereas in branched PGCs the same structural element most likely assumes the synclinal presentation.

Binding Sites↗