Apoptotic DNA fragmentation can be revealed in situ: An ultrastructural approach

A common pattern of apoptotic death is DNA cleavage, initially producing large fragments (50 kbp), followed by the production of nucleosomic/oligonucleosomic fragments. Nevertheless, apoptosis without DNA fragmentation, at least of the nucleosomic type, has been reported. To investigate the spatial relationship between DNA cleavage and chromatin condensation, we applied the TUNEL technique to the ultrastructural analysis of apoptotic cells. A modified method, utilizing a gold‐conjugated antidigoxigenin antibody, was carried out on U937 versus Molt‐4 cells, both exposed to UVB radiation or staurosporine treatment. Gold particle density in the different domains of apoptotic cells was evaluated by a four‐way ANOVA test. Gold labelling was more strongly localised in condensed chromatin than in the diffuse chromatin. U937 cells, which evidenced in vitro oligonucleosomic fragmentation after both UVB and staurosporine treatments, revealed a significantly higher gold particle density, when compared with Molt‐4, which did not show, on the other hand, oligonucleosomic cleavage even in the presence of ≤50 kbp cleavage. Thus, a correlation between DNA fragment sizes and gold particle density appears. TUNEL applied to electron microscopy is an effective approach to study the relationship between apoptotic chromatin condensation and DNA cleavage. Both these events indeed appear in the apoptotic nucleus, but their reciprocal correlation is still greatly unknown. Microsc. Res. Tech. 2009. © 2009 Wiley‐Liss, Inc.     

PCSK9 Affects Astrocyte Cholesterol Metabolism and Reduces Neuron Cholesterol Supplying In Vitro: Potential Implications in Alzheimer’s Disease

The Proprotein Convertase Subtilisin/Kexin Type 9 (PCSK9) involvement in Alzheimer’s disease (AD) is poorly investigated. We evaluated the in vitro PCSK9 modulation of astrocyte cholesterol metabolism and neuronal cholesterol supplying, which is fundamental for neuronal functions. Moreover, we investigated PCSK9 neurotoxic effects. In human astrocytoma cells, PCSK9 reduced cholesterol content (−20%; p < 0.05), with a greater effect in presence of beta amyloid peptide (Aβ) (−37%; p < 0.01). PCSK9 increased cholesterol synthesis and reduced the uptake of apoE-HDL-derived cholesterol (−36%; p < 0.0001), as well as the LDL receptor (LDLR) and the apoE receptor 2 (ApoER2) expression (−66% and −31%, respectively; p < 0.01). PCSK9 did not modulate ABCA1- and ABCG1-cholesterol efflux, ABCA1 levels, or membrane cholesterol. Conversely, ABCA1 expression and activity, as well as membrane cholesterol, were reduced by Aβ (p < 0.05). In human neuronal cells, PCSK9 reduced apoE-HDL-derived cholesterol uptake (−41%; p < 0.001) and LDLR/apoER2 expression (p < 0.05). Reduced cholesterol internalization occurred also in PCSK9-overexpressing neurons exposed to an astrocyte-conditioned medium (−39%; p < 0.001). PCSK9 reduced neuronal cholesterol content overall (−29%; p < 0.05) and increased the Aβ-induced neurotoxicity (p < 0.0001). Our data revealed an interfering effect of PCSK9, in cooperation with Aβ, on brain cholesterol metabolism leading to neuronal cholesterol reduction, a potentially deleterious effect. PCSK9 also exerted a neurotoxic effect, and thus represents a potential pharmacological target in AD.     

Evaluation of microalgae-based biorefinery alternatives

Microalgae-based biorefineries for the production of renewable biofuels like biodiesel, upgraded bio-oil, biochar, biogas and other high-value chemicals have received great attention in recent decades as potential major sources of energy for the future. Microalgae are a suitable species to produce biodiesel and other high energy density by-products; however, it is questionable whether a net energy gain can be realized or not considering the whole processing chain. In the present study, the energy balances of different algae-based biofuel and bioenergy production technologies are investigated in detail and compared to each other corresponding to a cradle-to-grave overall energetic analysis. The study includes cultivation, harvesting, cell pretreatments (cell disruption, drying, grinding), lipid extraction, transesterification, gasification and hydrothermal liquefaction with bio-oil stabilization and hydroprocessing. The energy consumption and energy gain are estimated for each operational step to determine the net energy ratio (NER, energy output over energy input) for the overall technologies studied. Our detailed investigation enables to detect the most energy consuming unit operation, that is, the bottleneck point(s) of the microalgae-based technologies which should be still improved in the future for the sake of more efficient algae-based biorefineries. The investigation makes also possible to evaluate and compare the different large scale alternatives for biomass transformation. Positive energy balances with a NER value of 1.109 and 1.137 are found in two already existing processes: open raceway ponds and closed photobioreactors, respectively. Our work gives also a detailed algorithm that can be followed at the evaluation of other microalgae-based biorefineries.     

Calculated angular responses of an RPL dosemeter to photon and beta radiation

The calculated dose equivalent response as a function of the angle has been examined for the radiophotoluminescent (RPL) glass dosemeter that was exposed to narrow series X-ray, N-60, N-80, N-100, N-150, N-200, N-250, N-300, photon sources ((60)Co and (137)Cs) and beta-ray emitter ((90)Sr/(90)Y) while mounted on an ISO water slab phantom. The angular dose equivalent responses H(p)(10) and H(p)(0.07) were calculated using the Monte Carlo MCNPX code. The RPL dosemeter and the phantom were rotated in the horizontal and vertical planes from a variety of angles of interest. The results were compared with the experimental data. Good agreement was found between the measured and calculated values of the relative dose equivalent angular responses of the RPL dosemeter.     

A single current conveyor-based low voltage low power bootstrap circuit for ElectroCardioGraphy and ElectroEncephaloGraphy acquisition systems

In this letter we propose a novel low voltage and low power single-CCII bootstrap circuit specifically designed to be implemented as input stage in ElectroCardioGraphy (ECG) or ElectroEncephaloGraphy (EEG) acquisition systems. The proposed circuit implements only a second generation current conveyor that has been designed to obtain, at X and Z nodes, reduced parasitic impedances, so improving CCII performance. Moreover, simulation results are also presented for a two electrodes ECG system. The circuit, designed in a standard 0.35 μm CMOS technology, shows low voltage (1.5 V) low power (28 μW) characteristics, so it is particularly suitable for portable applications.     

Selective hydrogenation of styrene. II. Poisoning of Pd/Al2O3 by thiophene and pyridine

The poisoning of a commercial Pd/Al₂O₃ catalyst by pyridine and thiophene during the selective hydrogenation of styrene to ethylbenzene was studied. It was found that the Pd electronic state is the main factor controlling the interaction between the metal and the poisons. Pyridine added to the non-poisoned feed in a pulse produces a modification in the Pd electronic state and a decrease in conversion, but, within certain limits, inhibits the adsorption of more pyridine or thiophene molecules.     

Intraoperative exchange of the endotracheal tube using the Cook C-CAE airway exchange catheter

The Cook airway exchange catheter is mainly used in ICU patients to exchange endotracheal tubes. We report three cases where this device was used during anaesthesia in patients with damaged tubes in critical circumstances (oropharyngeal bleeding, head and neck surgery). It allowed a fast and atraumatic exchange of the tubes.