Graphene oxide impairs the pollen performance of Nicotiana tabacum and Corylus avellana suggesting potential negative effects on the sexual reproduction of seed plants

The production of graphene based materials (GBMs) is steadily increasing but the effects of the possible release of GBMs in the environment are far from being understood. Graphene oxide (GO) is among the most active GBMs and it causes widely varying effects on the vegetative body of seed plants. However, nothing is known yet about its potential effects on the reproductive process. This study addresses the effects of GO on pollen germination and pollen tube elongation in the model species Nicotiana tabacum and in the non-model species Corylus avellana. In vitro germination experiments were conducted without or with GO (control and treated samples, respectively) at concentrations of 25, 50 and 100 μg mL−1. Pollen germination and tube elongation were affected at GO concentrations ≥50 μg mL−1, decreasing by 20% and 19% in N. tabacum and by 68% and 58% in C. avellana, respectively. GO did not affect the viability of N. tabacum pollen, but doubled the frequency of bent tubes. Microscopy observations of pollen tubes exposed to a cellpermeant, dual-excitation ratiometric pH indicator revealed that GO affected the intracellular pH homeostasis. Further germination experiments on C. avellana conducted by inverting the pH conditions of the control and treated (100 μg GO mL−1) samples demonstrated that the main factor influencing the pollen performance is the acidic properties of GO. This might affect the reproductive process of numerous seed plants thus being relevant from an environmental point of view

Bovine Models of Human Retinal Disease: Effect of Perivascular Cells on Retinal Endothelial Cell Permeability

Background: Diabetic vascular complications affect both the macro- and microvasculature. Microvascular pathology in diabetes may be mediated by biochemical factors that precipitate cellular changes at both the gene and protein levels. In the diabetic retina, vascular pathology is found mainly in microvessels, including the retinal precapillary arterioles, capillaries and venules. Macular oedema secondary to breakdown of the inner blood-retinal barrier is the most common cause of vision impairment in diabetic retinopathy. Müller cells play a critical role in the trophic support of retinal neurons and blood vessels. In chronic diabetes, Müller cells are increasingly unable to maintain their supportive functions and may themselves undergo changes that exacerbate the retinal pathology. The consequences of early diabetic changes in retinal cells are primarily considered in this thesis. Aims: This thesis aims to investigate the effect of perivascular cells (Müller cells, RPE, pericytes) on retinal endothelial cell permeability using an established in vitro model. Methods: Immunohistochemistry, cell morphology and cell growth patterns were used to characterise primary bovine retinal cells (Müller cells, RPE, pericytes and endothelial cells). An in vitro model of the blood-retinal barrier was refined by coculturing retinal endothelial cells with perivascular cells (Müller cells or pericytes) on opposite sides of a permeable Transwell filter. The integrity of the barrier formed by endothelial cells was assessed by transendothelial electrical resistance (TEER) measurements. Functional characteristics of endothelial cells were compared with ultrastructural morphology to determine if different cell types have barrier-enhancing effects on endothelial cell cultures. Once the co-culture model was established, retinal endothelial cells and Müller cells were exposed to different environmental conditions (20% oxygen, normoxia; 1% oxygen, hypoxia) to examine the effect of perivascular cells on endothelial cell permeability under reduced oxygen conditions. Barrier integrity was assessed by TEER measurements and permeability was measured by passive diffusion of radiolabelled tracers from the luminal to the abluminal side of the endothelial cell barrier. A further study investigated the mechanism of laser therapy on re-establishment of retinal endothelial cell barrier integrity. Müller cells and RPE, that comprise the scar formed after laser photocoagulation, and control cells (Müller cells and pericytes, RPE cells and ECV304, an epithelial cell line) were grown in long-term culture and treated with blue-green argon laser. Lasered cells were placed underneath confluent retinal endothelial cells growing on a permeable filter, providing conditioned medium to the basal surface of endothelial cells. The effect of conditioned medium on endothelial cell permeability was determined, as above. Results: Co-cultures of retinal endothelial cells and Müller cells on opposite sides of a permeable filter showed that Müller cells can enhance the integrity of the endothelial cell barrier, most likely through soluble factors. Low basal resistances generated by endothelial cells from different retinal isolations may be the result of erratic growth characteristics (determined by ultrastructural studies) or the selection of vessel fragments without true â barrier characteristicsâ in the isolation step. When Müller cells were co-cultured in close apposition to endothelial cells under normoxic conditions, the barrier integrity was enhanced and permeability was reduced. Under hypoxic conditions, Müller cells had a detrimental effect on the integrity of the endothelial cell barrier and permeability was increased in closely apposed cells. Conditioned medium from long-term cultured Müller cells and RPE that typically comprise the scar formed after lasering, enhanced TEER and reduced permeability of cultured endothelial cells. Conclusions: These studies confirm that bovine tissues can be used as a suitable model to investigate the role of perivascular cells on the permeability of retinal endothelial cells. The dual effect of Müller cells on the retinal endothelial cell barrier under different environmental conditions, underscores the critical role of Müller cells in regulating the blood-retinal barrier in health and disease. These studies also raise the possibility that soluble factor(s) secreted by Müller cells and RPE subsequent to laser treatment reduce the permeability of retinal vascular endothelium. Future studies to identify these factor(s) may have implications for the clinical treatment of macular oedema secondary to diseases including diabetic retinopathy

Bovine Models of Human Retinal Disease: Effect of Perivascular Cells on Retinal Endothelial Cell Permeability

Background: Diabetic vascular complications affect both the macro- and microvasculature. Microvascular pathology in diabetes may be mediated by biochemical factors that precipitate cellular changes at both the gene and protein levels. In the diabetic retina, vascular pathology is found mainly in microvessels, including the retinal precapillary arterioles, capillaries and venules. Macular oedema secondary to breakdown of the inner blood-retinal barrier is the most common cause of vision impairment in diabetic retinopathy. Müller cells play a critical role in the trophic support of retinal neurons and blood vessels. In chronic diabetes, Müller cells are increasingly unable to maintain their supportive functions and may themselves undergo changes that exacerbate the retinal pathology. The consequences of early diabetic changes in retinal cells are primarily considered in this thesis. Aims: This thesis aims to investigate the effect of perivascular cells (Müller cells, RPE, pericytes) on retinal endothelial cell permeability using an established in vitro model. Methods: Immunohistochemistry, cell morphology and cell growth patterns were used to characterise primary bovine retinal cells (Müller cells, RPE, pericytes and endothelial cells). An in vitro model of the blood-retinal barrier was refined by coculturing retinal endothelial cells with perivascular cells (Müller cells or pericytes) on opposite sides of a permeable Transwell filter. The integrity of the barrier formed by endothelial cells was assessed by transendothelial electrical resistance (TEER) measurements. Functional characteristics of endothelial cells were compared with ultrastructural morphology to determine if different cell types have barrier-enhancing effects on endothelial cell cultures. Once the co-culture model was established, retinal endothelial cells and Müller cells were exposed to different environmental conditions (20% oxygen, normoxia; 1% oxygen, hypoxia) to examine the effect of perivascular cells on endothelial cell permeability under reduced oxygen conditions. Barrier integrity was assessed by TEER measurements and permeability was measured by passive diffusion of radiolabelled tracers from the luminal to the abluminal side of the endothelial cell barrier. A further study investigated the mechanism of laser therapy on re-establishment of retinal endothelial cell barrier integrity. Müller cells and RPE, that comprise the scar formed after laser photocoagulation, and control cells (Müller cells and pericytes, RPE cells and ECV304, an epithelial cell line) were grown in long-term culture and treated with blue-green argon laser. Lasered cells were placed underneath confluent retinal endothelial cells growing on a permeable filter, providing conditioned medium to the basal surface of endothelial cells. The effect of conditioned medium on endothelial cell permeability was determined, as above. Results: Co-cultures of retinal endothelial cells and Müller cells on opposite sides of a permeable filter showed that Müller cells can enhance the integrity of the endothelial cell barrier, most likely through soluble factors. Low basal resistances generated by endothelial cells from different retinal isolations may be the result of erratic growth characteristics (determined by ultrastructural studies) or the selection of vessel fragments without true â barrier characteristicsâ in the isolation step. When Müller cells were co-cultured in close apposition to endothelial cells under normoxic conditions, the barrier integrity was enhanced and permeability was reduced. Under hypoxic conditions, Müller cells had a detrimental effect on the integrity of the endothelial cell barrier and permeability was increased in closely apposed cells. Conditioned medium from long-term cultured Müller cells and RPE that typically comprise the scar formed after lasering, enhanced TEER and reduced permeability of cultured endothelial cells. Conclusions: These studies confirm that bovine tissues can be used as a suitable model to investigate the role of perivascular cells on the permeability of retinal endothelial cells. The dual effect of Müller cells on the retinal endothelial cell barrier under different environmental conditions, underscores the critical role of Müller cells in regulating the blood-retinal barrier in health and disease. These studies also raise the possibility that soluble factor(s) secreted by Müller cells and RPE subsequent to laser treatment reduce the permeability of retinal vascular endothelium. Future studies to identify these factor(s) may have implications for the clinical treatment of macular oedema secondary to diseases including diabetic retinopathy

Biofouling of crypts of historical and architectural interest at la Plata Cemetery (Argentina)

Cemeteries are part of the cultural heritage of urban communities, containing funerary crypts and monuments of historical and architectural interest. Efforts aimed at the conservation of these structures must target not only the abiotic stresses that cause their destruction, such as light and humidity, but also biofouling by biotic agents. The purpose of this study was to assess the development of biofouling of several historically and architecturally valuable crypts at La Plata Cemetery (Argentina). Samples obtained from the biofilms, lichens, and fungal colonies that had developed on the marble surfaces and cement mortar of these crypts were analyzed by conventional microbiological techniques and by scanning electron microscopy. The lichens were identified as Caloplaca austrocitrina, Lecanora albescens, Xanthoparmelia farinosa and Xanthoria candelaria, the fungi as Aspergillus sp., Penicillium sp., Fusarium sp., Candida sp. and Rhodotorula sp., and the bacteria as Bacillus sp. and Pseudomonas sp. The mechanisms by which these microorganisms cause the aesthetic and biochemical deterioration of the crypts are discussed

Desiccation tolerance and lichenization: a case study with the aeroterrestrial microalga Trebouxia sp. (Chlorophyta)

Coccoid algae in the Trebouxia genus are the most common photobionts of chlorolichens but are only sporadically found in soil or bark outside of a lichen. They all appear to be desiccation tolerant, i.e. they can survive drying to water contents of below 10 %. However, little is known about their longevity in the dry state and to which extent lichenization can influence it. Here, we studied the longevity in the dry state of the lichenized alga (LT) Trebouxia sp. in the lichen Parmotrema perlatum, in comparison with axenically grown cultures (CT) isolated from the same lichen. We report on chlorophyll fluorescence emission and reactive oxygen species (ROS) production before desiccation, after 15\u201345 days in the dry state under different combinations of light and air humidity and after recovery for 1 or 3 days in fully hydrated conditions. Both the CT and the LT were able to withstand desiccation under high light (120 lmol photons m-2 s-1 for 14 h per day), but upon recovery after 45 days in the dry state the performance of the CT was better than that of the LT. By contrast, the quenching of excess light energy was more efficient in the LT, at high relative humidities especially. ROS production in the LT was influenced mostly by light exposure, whereas the CT showed an oxidative burst independent of the light conditions. Although lichenization provides benefits that are essential for the survival of the photobiont in high-light habitats, Trebouxia sp. can withstand protracted periods of photo-oxidative stress even outside of a lichen thallus

Notulae to the Italian flora of algae, bryophytes, fungi and lichens: 5

In this contribution, new data concerning bryophytes, fungi, and lichens of the Italian flora are presented. It includes new records and confirmations for the bryophyte genera Diplophyllum and Ptychostomum, the fungal genera Arrhenia, Gymnosporangium, and Sporidesmium and the lichen genera Arthonia, Coenogonium, Flavoplaca, Gyalolechia, Parmotrema, Peltigera, Pterygiopsis, Squamarina, Tornabea, and Waynea

Drought-induced xylem cavitation and hydraulic deterioration: Risk factors for urban trees under climate change?

5noUrban trees help towns to cope with climate warming by cooling both air and surfaces. The challenges imposed by the urban environment, with special reference to low water availability due to the presence of extensive pavements, result in high rates of mortality of street trees, that can be increased by climatic extremes. We investigated the water relations and xylem hydraulic safety/efficiency of Quercus ilex trees growing at urban sites with different percentages of surrounding impervious pavements. Seasonal changes of plant water potential and gas exchange, vulnerability to cavitation and embolism level, and morpho-anatomical traits were measured. We found patterns of increasing water stress and vulnerability to drought at increasing percentages of impervious pavement cover, with a consequent reduction in gas exchange rates, decreased safety margins toward embolism development, and increased vulnerability to cavitation, suggesting the occurrence of stress-induced hydraulic deterioration. The amount of impermeable surface and chronic exposure to water stress influence the site-specific risk of drought-induced dieback of urban trees under extreme drought. Besides providing directions for management of green spaces in towns, our data suggest that xylem hydraulics is key to a full understanding of the responses of urban trees to global change.partially_openopenSavi, Tadeja; Bertuzzi, Stefano; Branca, Salvatore; Tretiach, Mauro; Nardini, AndreaSavi, Tadeja; Bertuzzi, Stefano; Branca, Salvatore; Tretiach, Mauro; Nardini, Andre

Seasonal variations of PAHs content and distribution patterns in a mixed land use area: A case study in NE Italy with the transplanted lichen Pseudevernia furfuracea

The seasonal differences of the polycyclic aromatic hydrocarbons (PAHs) content in lichen transplants were investigated in an area of ca. 40 square kilometers in NE Italy characterized by different land use. Two sets of samples of the epiphytic lichen Pseudevernia furfuracea were collected in a pristine area of the Carnic Alps and transplanted to 40 exposure sites for a period of two months, respectively in late winter and in summer. Results revealed a pronounced difference between the two seasons in terms of PAH content and distribution patterns. After the summer exposure the PAH concentrations in the transplants were more than one order of magnitude lower than after the winter exposure (ranging from 48.22 to 272.73 ng g 121 dw and from 289.73 to 1575.85 ng g 121 dw in the summer and winter samples respectively). Also the main emission sources changed, mostly due to the drastic reduction in the emissions by wood burning for domestic heating and to the different meteorological conditions. In summer PAHs degradation was enhanced by intense UV radiation, high temperatures, and presence of ozone. The implications of these findings for the biomonitoring of PAHs pollution are addressed