Comparative study of heparin- and toluidine blue positive mast cells in porcine lumbar spinal ganglia

In the present study, toluidine blue for metachromasia and berberine sulfate for heparin fluorescence were used to determine the localisation and distribution of mast cells as well as the percent of hepa-rin-positive cells (MCH) in normal lumbar spinal ganglia (dorsal root ganglia) of domestic swine. Mast cells density was established after estimating the number of these cells per ganglion. Mast cells with metachromasia (MCTB) were observed predominantly in the ganglion capsule near the blood vessels. The number of mast cells inside the ganglia (2.10±1.45 in males and 2.20±1.03 in females) was significantly lower than in the capsule (13.30±1.95 in males and 13.60±2.42 in females) in both genders (P<0.001). Sexual dimorphism of the studied parameters was not established except for the slightly higher number of mast cells localised inside the left spinal ganglia of females than in males (P<0.05). The localisation of heparin-positive mast cells and the ratio between them and mast cells stained with toluidine blue (almost 2:1) was also determined. The percentage of heparin-positive mast cells in the ganglion capsule was 4 %, whereas inside the ganglion – 40%

Le bénévolat des jeunes

What makes young people want to learn, commit and become involved in an activity? This issue is of particular interest to teachers, but also to employers. In order to provide some answers, the authors of this book are interested in a specific population: young people aged 16 to 25 who have freely chosen to get involved in associations as varied as sport, politics, the environment, humanitarian work or events. Based on interviews, this study traces the volunteer careers of some forty young women and men from all social categories. They proudly recall the responsibilities that were entrusted to them very early on in a structured, flexible and benevolent associative world. Their testimonies help to highlight the many learning and skills that the volunteer experience has enabled them to develop

Phosphorus imbalance in the global ocean?

The phosphorus budget of the pre-human modern ocean is constrained applying the most recent estimates of the natural riverine, eolian, and ice-rafted input fluxes, the phosphorus burial in marine sediments, and the hydrothermal removal of dissolved phosphate from the deep ocean. This review of current flux estimates indicates that the phosphorus budget of the ocean is unbalanced since the accumulation of phosphorus in marine sediments and altered oceanic crust exceeds the continental input of particulate and dissolved phosphorus. The phosphorus mass balance is further tested considering the dissolved phosphate distribution in the deep water column, the marine export production of particulate organic matter, rain rates of phosphorus to the seafloor, benthic dissolved phosphate fluxes, and the organic carbon to phosphorus ratios in marine particles. These independent data confirm that the phosphate and phosphorus budgets were not at steadystate in the pre-human global ocean. The ocean is losing dissolved phosphate at a rate of ≥ 11.6 x 1010 mol yr-1 corresponding to a decline in the phosphate inventory of ≥ 4.5 % kyr-1. Benthic data show that phosphate is preferentially retained in pelagic deep-sea sediments where extended oxygen exposure times favor the degradation of particulate organic matter and the up-take of phosphate in manganese and iron oxides and hydroxides. Enhanced C : P regeneration ratios observed in the deep water column (>400 m water depth) probably reflect the preferential burial of phosphorus in pelagic sediments. Excess phosphate is released from continental margin sediments deposited in low-oxygen environments. The dissolved oxygen threshold value for the enhanced release of dissolved phosphate is ~20 μM. Benthic phosphate fluxes increase drastically when oxygen concentrations fall below this value

Ocean circulation in the Toarcian (Early Jurassic), a key control on deoxygenation and carbon burial on the European Shelf

The Toarcian Oceanic Anoxic Event (T-OAE, ∼183 My) was a long-lasting episode of ocean deoxygenation during the Early Jurassic. The event is related to a period of global warming and characterized by major perturbations to the hydrological and carbon cycles with high rates of organic matter burial in shelf seas. Ocean circulation during the Toarcian and its influence on marine biogeochemical cycles are still not fully understood. Here,we assess the spatial extent of anoxia in the NW Tethys Ocean during the T-OAE, the relationship with ocean circulation and the impact on organic carbon burial, using new and existing sedimentary records from the European Epicontinental Shelf (EES) in combination with general circulation model results. We demonstrate that bottom waters on the southwestern part of the shelf were mainly oxic during the T-OAE, while those in the northeastern basins were mostly anoxic or even sulfidic. Results for two ocean-atmosphere models (FOAM and MITgcm) suggest the presence of a strong clockwise gyre over the EES, which brought oxygenated equatorial waters from the Tethys Ocean to the southern shelf. The northward limb of the gyre was significantly weakened due to the rough bathymetry of the northern shelf, making this relative small region highly sensitive to local ocean stratification. These sluggish ocean dynamics promoted bottom water anoxia and enhanced burial of organic carbon in the northeastern basins, which accounted for 3–5% of the total carbon extracted from the ocean-atmosphere system as recorded by the positive carbon isotope shift

Arterial vascularisation of pig’s auditory tube with respect to a. palatina ascendens – a corrosion cast and morphometric study

The aim of this study was to determine species-specific features of arterial vascularisation of the audi-tory tube of domestic pigs as a segment connecting the nasopharynx and the middle ear with regard to the increasing role of pigs as most appropriate model of human biomedical research. The arterial branches involved in the vascularisation of the auditory tube were described on corrosion casts. It was found out that in the direction of the middle ear, the tube received blood from branches of a. palatina ascendens, a. meningea media, a. temporalis profunda caudalis and rete mirabile epidurale rostrale, out of which the first of enumerated arteries was the most involved. In the majority of cases (87.5%) it gave off two branches that ramified in the lateral and medial walls of the tube. For the first time, it was demonstrated that a. palatina ascendens was separated from the facial artery and not from a. lingualis. The measurements on casts showed that the diameter of left a. palatina ascendens was sta-tistically significantly larger than right one in both sexes, and that average diameters of either right or left arteries were larger in males. The results allowed concluding that a. palatina ascendens was pre-dominantly involved in the arterial blood supply of porcine auditory tube

The global marine phosphorus cycle: Response to climate change and feedbacks on ocean biogeochemistry. Geologica Ultraiectina (329)

This thesis focuses on the marine phosphorus (P) cycle and its response to changing environmental conditions, particularly those associated with glacial-interglacial cycles of the late Pleistocene and Ocean Anoxic Events in the Cretaceous. From a box model of the ocean phosphorus, organic carbon and oxygen cycles, climate change scenarios are applied representing these events. The effects of continental supply of reactive P, oceanic mixing, and sea level on the marine P cycle are examined on glacial-interglacial timescales. Results show that mixing is a dominant forcing during early glaciation and leads to an initial lowering of oceanic primary production, while sea level fall is the dominant forcing during late glaciation, enhancing nutrient supply to the open ocean. Post glacial periods are times of peak productivity, and primary production is generally lower during glaciations relative to post glacial periods, arguing against the biological pump hypothesis for CO2 drawdown. When shelf erosion during sea level low stands and particulate matter re-routing to the open ocean via submarine river canyons are implemented as part of the glacial-interglacial transition scenario, the results indicate that deep sea oxygen levels may lower significantly, mainly due to the supply of new material from the shelves and particulate organic matter bypassing the coastal zone. Deep-sea oxygen demand is decoupled from primary productivity in the open ocean and the phosphorus burial does not reflect ocean fertilization. When the box model is adapted to Cretaceous ocean conditions, Oceanic Anoxic Events (OAEs) can be triggered by enhanced P supply from land, for an ocean with wide continental shelves, slow circulation and high sea surface temperatures. The system is most sensitive to oceanic mixing. Model results imply OAEs can be sustained by P recycling from sediments due to low oxygen in the water column. These results are corroborated by P burial data from the geological record for OAE2. A sensitivity analysis demonstrates that low mixing of ocean waters (poor ventilation) and enhanced sedimentary P recycling are necessary to achieve ocean anoxia. Phosphorus burial in deep sea sediments is investigated as a function of bottom water oxygen and organic matter flux to the sediment water interface, using a mechanistic reactive transport model for sediment diagenesis. Hypoxic, oligotrophic conditions are thus identified as optimum for P recycling from the sediment. The mechanistically derived redox P burial is implemented in the box model of the marine P, oxygen and organic carbon cycles. Results show that, although deep-sea burial of reactive P phases changes, the biogeochemical cycling in the ocean is not impacted

Numerical study of the factors affecting the cycling of iron, sulfur and phosphorus in lake sediments

In recent years, reaction transport models have gained importance in the study of diagenesis, which describes the chemical, biological and physical processes that take place in sediments. This project reports on factors influencing chemical profiles in lake sediments through an exploration of a generic reaction transport model which includes representations of the major reactions involved in the cycling of iron, sulfur and phosphorus. We have performed a global sensitivity analysis examining the steady state effects of physical, kinetic and thermodynamic factors on the magnitude, shape and burial concentrations of chemical profiles of iron, sulfur and phosphorus-bearing species. The environmental conditions were varied within a broad range typical of lake sediments. The exploration demonstrates the importance of the nature of boundary conditions (i.e. characteristics of the water column) and their coupling to the water column dynamics. The study additionally points to some chemical mechanisms such as precipitation of vivianite and scavenging of vivianite by sulfide having a dominant influence on the depth profiles of chemical species. Investigation also shows the importance of physical transport processes such as bioturbation near the sediment water interface and sedimentation velocity. Additionally, the distribution of reaction rates with depth and their role in shaping the profiles of chemical concentrations under typical environmental conditions were investigated

Nitrogen dynamics during the Cenomanian-Turonian oceanic Anoxic Event 2: A model study for the proto-North Atlantic

Evidence from sediment core records and model studies suggest that increased nutrient supply played a key role in the initiation of the Cenomanian-Turonian oceanic anoxic event 2 (OAE2; ~94 Ma). However, the relative roles of nitrogen (N) and phosphorus (P) availability in controlling primary productivity during the event are not fully understood. Here, we expand an existing multi-box model of the coupled cycles of P, carbon and oxygen in the proto-North Atlantic ocean with the marine N cycle. With the updated version of the model, we test the hypothesis that enhanced availability of P can fuel N2-fixation, increase primary productivity and drive large parts of the proto-North Atlantic to anoxia during OAE2. In a sensitivity analysis, we demonstrate that N dynamics in the proto-North Atlantic respond strongly to variations in oxygen and P supply from the Pacific Ocean and to changes in circulation. The implemented N cycle weakly modifies the carbon cycle, implying that P was the major nutrient controlling primary productivity during OAE2. Our model suggests that both N2-fixation and upwelling of recycled ammonium (NH4+) were enhanced during OAE2 and that N2-fixation was the major source of N in the proto-North Atlantic. Denitrification was more important in the water column than in sediments, with high rates in the open ocean and in the Western Interior. High P inputs in the proto-North Atlantic led to widespread N2-fixation, which more than compensated for the loss of N through denitrification. As a consequence, rates of primary productivity and organic carbon burial were high