Microsurgical and laser ablation analysis of interactions between the zones and layers of the tomato shoot apical meristern

Plants exhibit life-long organogenic and histogenic activity in a specialised organ, the shoot apical meristem. Leaves and flowers are formed within the ring-shaped peripheral zone, which surrounds the central zone, the site of the stem cells. We have undertaken a series of high-precision laser ablation and microsurgical tissue removal experiments to test the functions of different parts of the tomato meristem, and to reveal their interactions. Ablation of the central zone led to ectopic expression of the WUSCHEL gene at the periphery, followed by the establishment of a new meristem centre. After the ablation of the central zone, organ formation continued without a lag. Thus, the central zone does not participate in organogenesis, except as the ultimate source of founder cells. Microsurgical removal of the external L-1 layer induced periclinal cell divisions and terminal differentiation in the subtending layers. In addition, no organs were initiated in areas devoid of L-1, demonstrating an important role of the L-1 in organogenesis. L-1 ablation had only local effects, an observation that is difficult to reconcile with phyllotaxis theories that invoke physical tension operating within the meristem as a whole. Finally, regeneration of L-1 cells was never observed after ablation. This shows that while the zones of the meristem show a remarkable capacity to regenerate after interference, elimination of the L-1 layer is irreparable and causes terminal differentiation.

Characterization of granite matrix porosity and pore-space geometry by in situ and laboratory methods

Most available studies of interconnected matrix porosity of crystalline rocks are based on laboratory investigations; that is, work on samples that have undergone stress relaxation and were affected by drilling and sample preparation. The extrapolation of the results to in situ conditions is therefore associated with considerable uncertainty, and this was the motivation to conduct the ‘in situ Connected Porosity’ experiment at the Grimsel Test Site (Central Swiss Alps). An acrylic resin doped with fluorescent agents was used to impregnate the microporous granitic matrix in situ around an injection borehole, and samples were obtained by overcoring. The 3-D structure of the porespace, represented by microcracks, was studied by U-stage fluorescence microscopy. Petrophysical methods, including the determination of porosity, permeability and P -wave velocity, were also applied. Investigations were conducted both on samples that were impregnated in situ and on non-impregnated samples, so that natural features could be distinguished from artefacts. The investigated deformed granites display complex microcrack populations representing a polyphase deformation at varying conditions. The crack population is dominated by open cleavage cracks in mica and grain boundary cracks. The porosity of non-impregnated samples lies slightly above 1 per cent, which is 2–2.5 times higher than the in situ porosity obtained for impregnated samples. Measurements of seismic velocities (Vp ) on spherical rock samples as a function of confining pressure, spatial direction and water saturation for both non-impregnated and impregnated samples provide further constraints on the distinction between natural and induced crack types. The main conclusions are that (1) an interconnected network of microcracks exists in the whole granitic matrix, irrespective of the distance to ductile and brittle shear zones, and (2) conventional laboratory methods overestimate the matrix porosity. Calculations of contaminant transport through fractured media often rely on matrix diffusion as a retardation mechanism.

S100A1 and S100B expression patterns identify differentiation status of human articular chondrocytes.

Many studies in the field of cell-based cartilage repair have focused on identifying markers associated with the differentiation status of human articular chondrocytes (HAC) that could predict their chondrogenic potency. A previous study from our group showed a correlation between the expression of S100 protein in HAC and their chondrogenic potential. The aims of the current study were to clarify which S100 proteins are associated with HAC differentiation status and to provide an S100-based assay for measuring HAC chondrogenic potential. The expression patterns of S100A1 and S100B were investigated in cartilage and in HAC cultured under conditions promoting dedifferentiation (monolayer culture) or redifferentiation (pellet culture or BMP4 treatment in monolayer culture), using characterized antibodies specifically recognizing S100A1 and S100B, by immunohistochemistry, immunocytochemistry, Western blot, and gene expression analysis. S100A1 and S100B were expressed homogeneously in all cartilage zones, and decreased during dedifferentiation. S100A1, but not S100B, was re-expressed in pellets and co-localized with collagen II. Gene expression analysis revealed concomitant modulation of S100A1, S100B, collagen type II, and aggrecan: down-regulation during monolayer culture and up-regulation upon BMP4 treatment. These results strongly support an association of S100A1, and to a lesser extent S100B, with the HAC differentiated phenotype. To facilitate their potential application, we established an S100A1/B-based flow cytometry assay for accurate assessment of HAC differentiation status. We propose S100A1 and S100B expression as a marker to develop potency assays for cartilage regeneration cell therapies, and as a redifferentiation readout in monolayer cultures aiming to investigate stimuli for chondrogenic induction.

Computer planned, image-guided combined resection and ablation for bilobar colorectal liver metastases

For patients with extensive bilobar colorectal liver metastases (CRLM), initial surgery may not be feasible and a multimodal approach including microwave ablation (MWA) provides the only chance for prolonged survival. Intraoperative navigation systems may improve the accuracy of ablation and surgical resection of so-called "vanishing lesions", ultimately improving patient outcome. Clinical application of intraoperative navigated liver surgery is illustrated in a patient undergoing combined resection/MWA for multiple, synchronous, bilobar CRLM. Regular follow-up with computed tomography (CT) allowed for temporal development of the ablation zones. Of the ten lesions detected in a preoperative CT scan, the largest lesion was resected and the others were ablated using an intraoperative navigation system. Twelve months post-surgery a new lesion (Seg IVa) was detected and treated by trans-arterial embolization. Nineteen months post-surgery new liver and lung metastases were detected and a palliative chemotherapy started. The patient passed away four years after initial diagnosis. For patients with extensive CRLM not treatable by standard surgery, navigated MWA/resection may provide excellent tumor control, improving longer-term survival. Intraoperative navigation systems provide precise, real-time information to the surgeon, aiding the decision-making process and substantially improving the accuracy of both ablation and resection. Regular follow-ups including 3D modeling allow for early discrimination between ablation zones and recurrent tumor lesions.

Ellis-van Creveld Syndrome in Grey Alpine Cattle: Morphologic, Immunophenotypic, and Molecular Characterization

Ellis-van Creveld (EvC) syndrome is a human autosomal recessive disorder caused by a mutation in either the EVC or EVC2 gene, and presents with short limbs, polydactyly, and ectodermal and heart defects. The aim of this study was to understand the pathologic basis by which deletions in the EVC2 gene lead to chondrodysplastic dwarfism and to describe the morphologic, immunohistochemical, and molecular hallmarks of EvC syndrome in cattle. Five Grey Alpine calves, with a known mutation in the EVC2 gene, were autopsied. Immunohistochemistry was performed on bone using antibodies to collagen II, collagen X, sonic hedgehog, fibroblast growth factor 2, and Ki67. Reverse transcription polymerase chain reaction was performed to analyze EVC1 and EVC2 gene expression. Autopsy revealed long bones that were severely reduced in length, as well as genital and heart defects. Collagen II was detected in control calves in the resting, proliferative, and hypertrophic zones and in the primary and secondary spongiosa, with a loss of labeling in the resting zone of 2 dwarfs. Collagen X was expressed in hypertrophic zone in the controls but was absent in the EvC cases. In affected calves and controls, sonic hedgehog labeled hypertrophic chondrocytes and primary and secondary spongiosa similarly. FGF2 was expressed in chondrocytes of all growth plate zones in the control calves but was lost in most EvC cases. The Ki67 index was lower in cases compared with controls. EVC and EVC2 transcripts were detected. Our data suggest that EvC syndrome of Grey Alpine cattle is a disorder of chondrocyte differentiation, with accelerated differentiation and premature hypertrophy of chondrocytes, and could be a spontaneous model for the equivalent human disease.

Osteoclast-like cells on deproteinized bovine bone mineral and biphasic calcium phosphate: light and transmission electron microscopical observations.

OBJECTIVES The occurrence of multinucleated giant cells (MNGCs) on bone substitute materials has been recognized for a long time. However, there have been no studies linking material characteristics with morphology of the MNGCs. The aim was to analyze the qualitative differences of MNGCs on two commercially available calcium phosphate bone substitute materials retrieved from bone defects. MATERIAL AND METHODS Six defects were prepared bilaterally in the mandibular body of three mini pigs. The defects were randomly grafted with either deproteinized bovine bone mineral (DBBM) or biphasic calcium phosphate (BCP). After a healing period of four weeks, bone blocks were embedded in LR White resin. Three consecutive sections per defect were analyzed as follows: two with light microscopy using toluidine blue and tartrate-resistant acid phosphatase (TRAP) staining and one with transmission electron microscopy. RESULTS Multinucleated giant cells appeared on both biomaterials. On BCP, MNGCs had a flat morphology and were not observed in resorption lacunae. On DBBM, the MNGCs appeared more round and were often found in shallow concavities. MNGCs on both biomaterials demonstrated a varying degree of TRAP staining, with a tendency toward higher staining intensity of MNGCs on BCP. At the ultrastructural level, signs of superficial dissolution of BCP together with phagocytosis of minor fragments were observed. MNGCs on the surface of DBBM demonstrated sealing zones and ruffled borders, both features of mature osteoclasts. CONCLUSION MNGCs demonstrated distinctly different histological features depending on the bone substitute material used. Further research is warranted to understand the clinical implications of these morphological observations.

The 1987 debris flows in Switzerland: documentation and analysis

A great number of debris flows occurred during the flood catastrophes of the summer of 1987 in the Swiss Alps. Aerial photography, field investigations and eyewitness accounts documented and analysed the events. As an example of the reconstructed major events, the large debris flow in the Varuna valley involved an estimated peak discharge between 400 and 800 m3/s and an event magnitude of 200,000 m3. Several single pulses were observed; the duration of each of them appeared to be not more than a few minutes. Apart from incision into weak bedrock, the maximum erosion depth seemed to depend on the channel gradient. Based on approximately 600 events, typical starting zones and rainfall conditions are discussed with regard to the triggering conditions. Existing and new empirical formulae are proposed to estimate the most important flow parameters. These values are compared to debris flow data from Canada and Japan.

WOCAT - World Overview of Conservation Approaches and Technologies - Preliminary results from Eastern and Southern Africa

The World Overview of Conservation Approaches and Technologies (WOCAT) is a program of the World Association of Soil and Water Conservation (WASWC), organized as a consortium of several international institutions. The overall goal of WOCAT is to contribute to sustainable utilization of soil and water. WOCAT collects and analyzes information on soil and water conservation (SWC) technologies and approaches world-wide, and presents the collected information in computer databases and decision support systems, and in the form of handbooks, reports and maps readily accessible to SWC specialists and policy-makers world-wide. WOCAT has prepared a framework for the evaluation of soil and water conservation and has started data collection. The paper presents preliminary results with promising SWC technologies and approaches used in Eastern and Southern Africa. The first finding is that hardly any promising SWC activities could be found on common grazing lands. Analysis of the cropland shows some of the bio-physical and socioeconomic conditions under which certain SWC technologies and approaches are used, including land use types, climatic zones and land tenure, and looks at issues such as participation and costs. Furthermore, classification criteria for SWC technologies and approaches are discussed.