472 research outputs found
Resiliens ur ett trÀdperspektiv : en kartlÀggning av Malmö stads trÀdbestÄnd
TrÀden i staden bidrar med mÄnga ekosystemtjÀnster som Àr livsviktiga. Med
klimatförÀndringar skapas oro över hur trÀden i staden kan stÄ emot högre
temperaturer. Denna studie grundar sig i hur klimatförÀndringarna pÄverkar
stadens trÀdbestÄnd och hur resiliens kan skapas för att bÀttre förbereda
trÀdbestÄnden pÄ kommande störningar. Studien undersöker vad resiliens innebÀr
kopplat till trÀd och förvaltning av grönytor i stÀder. Vidare tittar vi nÀrmre pÄ hur
trÀdens förutsÀttningar i Malmö visar sig ur resilient perspektiv. Genom en GISvisualisering analyseras data kring trÀdens artdiversitet, Älder och rumslig
placering. Bakgrunden till varför det Àr en viktig frÄga styrks i litteraturstudien
som handlar om hur klimatförÀndringar drabbar stÀder. TrÀdens förutsÀttningar
sÀtts pÄ spel i en tid dÀr klimatet blir mer extremt och innebÀr störningar för bÄde
trÀd och mÀnniskor. Samtidigt visar forskning pÄ att just trÀden Àr en bidragande
faktor till hur vi fÄr ner temperaturerna i vÄra stÀder.The trees in the city provide many ecosystem services that are vital. With climate
change, concerns are being raised about how the trees in the city can withstand
the higher temperatures. This study is based on how climate change affects the
city's tree population and how resilience can be created to better prepare tree
resources for future disturbances. The study examines how resilience influence
the connection of trees and the management of green spaces in cities.
Furthermore, we take a closer look at how the conditions of the trees in Malmö
looks from a resilient perspective. A GIS analyzes data on tree species diversity,
age and spatial location. The reason why this is an important issue is
substantiated in the literature study which deals with how climate change affects
cities. The conditions of the trees are being jeopardized at a time when the climate
is becoming more extreme and causes disturbances for both trees and people. At
the same time, research is showing that trees are a contributing factor in how to
lower temperatures in our cities
Periodontal regenerative effect of a bovine hydroxyapatite/collagen block in one-wall intrabony defects in dogs: a histometric analysis
Principles of Periodontology
Periodontal diseases are among the most common diseases affecting humans. Dental biofilm is a contributor to the etiology of most periodontal diseases. It is also widely accepted that immunological and inflammatory responses to biofilm components are manifested by signs and symptoms of periodontal disease. The outcome of such interaction is modulated by risk factors (modifiers), either inherent (genetic) or acquired (environmental), significantly affecting the initiation and progression of different periodontal disease phenotypes. While definitive genetic determinants responsible for either susceptibility or resistance to periodontal disease have yet to be identified, many factors affecting the pathogenesis have been described, including smoking, diabetes, obesity, medications, and nutrition. Currently, periodontal diseases are classified based upon clinical disease traits using radiographs and clinical examination. Advances in genomics, molecular biology, and personalized medicine may result in new guidelines for unambiguous disease definition and diagnosis in the future. Recent studies have implied relationships between periodontal diseases and systemic conditions. Answering critical questions regarding hostâparasite interactions in periodontal diseases may provide new insight in the pathogenesis of other biomedical disorders. Therapeutic efforts have focused on the microbial nature of the infection, as active treatment centers on biofilm disruption by nonâsurgical mechanical debridement with antimicrobial and sometimes antiâinflammatory adjuncts. The surgical treatment aims at gaining access to periodontal lesions and correcting unfavorable gingival/osseous contours to achieve a periodontal architecture that will provide for more effective oral hygiene and periodontal maintenance. In addition, advances in tissue engineering have provided innovative means to regenerate/repair periodontal defects, based upon principles of guided tissue regeneration and utilization of growth factors/biologic mediators. To maintain periodontal stability, these treatments need to be supplemented with longâterm maintenance (supportive periodontal therapy) programs
In vitro evaluation of various bioabsorbable and nonresorbable barrier membranes for guided tissue regeneration
<p>Abstract</p> <p>Background</p> <p>Different types of bioabsorbable and nonresorbable membranes have been widely used for guided tissue regeneration (GTR) with its ultimate goal of regenerating lost periodontal structures. The purpose of the present study was to evaluate the biological effects of various bioabsorbable and nonresorbable membranes in cultures of primary human gingival fibroblasts (HGF), periodontal ligament fibroblasts (PDLF) and human osteoblast-like (HOB) cells <it>in vitro</it>.</p> <p>Methods</p> <p>Three commercially available collagen membranes [TutoDent<sup>Ÿ </sup>(TD), Resodont<sup>Ÿ </sup>(RD) and BioGide<sup>Ÿ </sup>(BG)] as well as three nonresorbable polytetrafluoroethylene (PTFE) membranes [ACE (AC), Cytoplast<sup>Ÿ </sup>(CT) and TefGen-FD<sup>Ÿ </sup>(TG)] were tested. Cells plated on culture dishes (CD) served as positive controls. The effect of the barrier membranes on HGF, PDLF as well as HOB cells was assessed by the Alamar Blue fluorometric proliferation assay after 1, 2.5, 4, 24 and 48 h time periods. The structural and morphological properties of the membranes were evaluated by scanning electron microscopy (SEM).</p> <p>Results</p> <p>The results showed that of the six barriers tested, TD and RD demonstrated the highest rate of HGF proliferation at both earlier (1 h) and later (48 h) time periods (<it>P </it>< 0.001) compared to all other tested barriers and CD. Similarly, TD, RD and BG had significantly higher numbers of cells at all time periods when compared with the positive control in PDLF culture (<it>P </it>†0.001). In HOB cell culture, the highest rate of cell proliferation was also calculated for TD at all time periods (<it>P </it>< 0.001). SEM observations demonstrated a microporous structure of all collagen membranes, with a compact top surface and a porous bottom surface, whereas the nonresorbable PTFE membranes demonstrated a homogenous structure with a symmetric dense skin layer.</p> <p>Conclusion</p> <p>Results from the present study suggested that GTR membrane materials, per se, may influence cell proliferation in the process of periodontal tissue/bone regeneration. Among the six membranes examined, the bioabsorbable membranes demonstrated to be more suitable to stimulate cellular proliferation compared to nonresorbable PTFE membranes.</p
Current concepts in periodontal bioengineering
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/73112/1/j.1601-6343.2005.00352.x.pd
The effect of experimental diabetes and glycaemic control on guided bone regeneration:histology and gene expression analyses
OBJECTIVES: To investigate the effect of experimental diabetes and metabolic control on intramembranous bone healing following guided bone regeneration (GBR). MATERIAL AND METHODS: Ninety-three Wistar rats were allocated to three experimental groups, healthy (H), uncontrolled diabetes (D) and controlled diabetes (CD). Twenty one days following diabetes induction, a standardised 5-mm defect was created at the mid-portion of each parietal bone. In 75 animals (25H, 25D, 25CD), one defect was treated with an intracranial and extracranial membrane according to the GBR principle, and one defect was left empty (control); five animals per group were then randomly sacrificed at 3, 7, 15, 30 and 60 days and processed for decalcified histology. In 18 animals (6H, 6D, 6CD), both defects were treated according to the GBR principle; three animals from each group were then randomly sacrificed at 7 and 15 days of healing and employed for gene expression analysis. RESULTS: Application of the GBR therapeutic principle led to significant bone regeneration even in the D group. However, at 15 and 30 days, the osteogenesis process was impaired by uncontrolled diabetes, as shown by the significant reduction in terms of defect closure (38-42%) and newly formed bone (54-61%) compared to the healthy group. The comparison of the D vs. H group at 15 days of healing yielded the largest number of genes with significantly differential expression, among which various genes associated with the ossification process (bmp4, ltbp4, thra and cd276) were identified. CONCLUSIONS: Uncontrolled diabetes seems to affect early phases of the bone regeneration following GBR. A misregulation of genes and pathways related to cell division, energy production, inflammation and osteogenesis may account for the impaired regeneration process in D rats. Further studies are warranted to optimise the GBR process in this medically compromised patient population
Isolation and characterisation of human gingival margin-derived STRO-1/MACS+ and MACSâ cell populations
Recently, gingival margin-derived stem/progenitor cells isolated via
STRO-1/magnetic activated cell sorting (MACS) showed remarkable periodontal
regenerative potential in vivo. As a second-stage investigation, the present
study's aim was to perform in vitro characterisation and comparison of the
stem/progenitor cell characteristics of sorted STRO-1-positive (MACS+) and
STRO-1-negative (MACSâ) cell populations from the human free gingival margin.
Cells were isolated from the free gingiva using a minimally invasive technique
and were magnetically sorted using anti-STRO-1 antibodies. Subsequently, the
MACS+ and MACSâ cell fractions were characterized by flow cytometry for
expression of CD14, CD34, CD45, CD73, CD90, CD105, CD146/MUC18 and STRO-1.
Colony-forming unit (CFU) and multilineage differentiation potential were
assayed for both cell fractions. Mineralisation marker expression was examined
using real-time polymerase chain reaction (PCR). MACS+ and MACSâ cell
fractions showed plastic adherence. MACS+ cells, in contrast to MACSâ cells,
showed all of the predefined mesenchymal stem/progenitor cell characteristics
and a significantly higher number of CFUs (P<0.01). More than 95% of MACS+
cells expressed CD105, CD90 and CD73; lacked the haematopoietic markers CD45,
CD34 and CD14, and expressed STRO-1 and CD146/MUC18. MACSâ cells showed a
different surface marker expression profile, with almost no expression of CD14
or STRO-1, and more than 95% of these cells expressed CD73, CD90 and
CD146/MUC18, as well as the haematopoietic markers CD34 and CD45 and CD105.
MACS+ cells could be differentiated along osteoblastic, adipocytic and
chondroblastic lineages. In contrast, MACSâ cells demonstrated slight
osteogenic potential. Unstimulated MACS+ cells showed significantly higher
expression of collagen I (P<0.05) and collagen III (P<0.01), whereas MACSâ
cells demonstrated higher expression of osteonectin (P<0.05; MannâWhitney).
The present study is the first to compare gingival MACS+ and MACSâ cell
populations demonstrating that MACS+ cells, in contrast to MACSâ cells,
harbour stem/progenitor cell characteristics. This study also validates the
effectiveness of the STRO-1/MACS+ technique for the isolation of gingival
stem/progenitor cells. Human free gingival margin-derived STRO-1/MACS+ cells
are a unique renewable source of multipotent stem/progenitor cells
- âŠ