Effects of acid-base imbalance on vascular reactivity

Acid-base homeostasis maintains systemic arterial pH within a narrow range. Whereas the normal range of pH for clinical laboratories is 7.35-7.45, in vivo pH is maintained within a much narrower range. In clinical and experimental settings, blood pH can vary in response to respiratory or renal impairment. This altered pH promotes changes in vascular smooth muscle tone with impact on circulation and blood pressure control. Changes in pH can be divided into those occurring in the extracellular space (pHo) and those occurring within the intracellular space (pHi), although, extracellular and intracellular compartments influence each other. Consistent with the multiple events involved in the changes in tone produced by altered pHo, including type of vascular bed, several factors and mechanisms, in addition to hydrogen ion concentration, have been suggested to be involved. The scientific literature has many reports concerning acid-base balance and endothelium function, but these concepts are not clear about acid-base disorders and their relations with the three known mechanisms of endothelium-dependent vascular reactivity: nitric oxide (NO/cGMP-dependent), prostacyclin (PGI2/cAMP-dependent) and hyperpolarization. During the last decades, many studies have been published and have given rise to confronting data on acid-base disorder and endothelial function. Therefore, the main proposal of this review is to provide a critical analysis of the state of art and incentivate researchers to develop more studies about these issues.

Maintenance of the corneal epithelium is carried out by germinative cells of its basal stratum and not by presumed stem cells of the limbus

The purpose of this investigation was to analyze the proliferative behavior of rabbit corneal epithelium and establish if any particular region was preferentially involved in epithelial maintenance. [3H]-thymidine was injected intravitreally into both normal eyes and eyes with partially scraped corneal epithelium. Semithin sections of the anterior segment were evaluated by quantitative autoradiography. Segments with active replication (on) and those with no cell division (off) were intermingled in all regions of the tissue, suggesting that the renewal of the epithelial surface of the cornea followed an on/off alternating pattern. In the limbus, heavy labeling of the outermost layers was observed, coupled with a few or no labeled nuclei in the basal stratum. This suggests that this region is a site of rapid cell differentiation and does not contain many slow-cycling cells. The conspicuous and protracted labeling of the basal layer of the corneal epithelium suggests that its cells undergo repeated cycles of replication before being sent to the suprabasal strata. This replication model is prone to generate label-retaining cells. Thus, if these are adult stem cells, one must conclude that they reside in the corneal basal layer and not the limbal basal layer. One may also infer that the basal cells of the cornea and not of the limbus are the ones with the main burden of renewing the corneal epithelium. No particular role in this process could be assigned to the cells of the basal layer of the limbal epithelium.

Modified atmosphere efficiency in the quality maintenance of Eva apples

Modified atmosphere is a method of food preservation that provides increased lifetime, decreases deterioration losses, and facilitates marketing. The objective of this study was to evaluate the efficiency of different plastic films in modifying the atmosphere around Eva apples to assure quality maintenance during postharvest storage. The fruits were cleaned and separated into three treatment groups: polypropylene, low density polyethylene, and high density polyethylene packing with a total of 5 fruits per package for each evaluation period. A group of control apples was not submitted to atmospheric modification. After the treatment, all fruits were stored at 0.5±0.5°C (cold storage) for up to 225 days. The analyses were performed at 45, 135, and 225 days after cold storage. Respiration, ethylene production, firmness, mass loss, total pectin, soluble pectin, soluble solids, total acidity, and epidermis background color of each treatment group were evaluated. The high density polyethylene film treatment did not show a decrease in ethylene production during storage and allowed the fruits to maintain a greater firmness and smaller percentage of mass loss during the study period. Moreover, the storage of the Eva apple cultivar under modified atmosphere allowed the preservation of quality for up to seven months.

Aloe vera extract as a promising treatment for the quality maintenance of minimally-processed table grapes

The effect of an edible film obtained from a commercial Aloe vera extract, on the quality maintenance of minimally processed grapes belonging to three different cultivars (Sugar One, Victoria and Black Magic) was evaluated by enzymatic (PPO, PME, β-GAL), physicochemical (pH, acidity, °Brix), and sensorial methods. All the analyzed parameters were measured in extracts obtained from minimally processed grapes packaged in ordinary atmosphere and stored at 4 °C for 15 days. Samples dipped into Aloe vera showed significant differences (p≤0.05) compared to untreated ones. The determination of such parameters and the evaluation of consumer acceptability were helpful to determine the effectiveness of the post-harvest treatment with Aloe vera for a storage period of 15 days.

Evolutionary Origin and Maintenance of Sociality in the Small Carpenter Bees

Many arthropods exhibit behaviours precursory to social life, including adult longevity, parental care, nest loyalty and mutual tolerance, yet there are few examples of social behaviour in this phylum. The small carpenter bees, genus Ceratina, provide important insights into the early stages of sociality. I described the biology and social behaviour of five facultatively social species which exhibit all of the preadaptations for successful group living, yet present ecological and behavioural characteristics that seemingly disfavour frequent colony formation. These species are socially polymorphic with both / solitary and social nests collected in sympatry. Social colonies consist of two adult females, one contributing both foraging and reproductive effort and the second which remains at the nest as a passive guard. Cooperative nesting provides no overt reproductive benefits over solitary nesting, although brood survival tends to be greater in social colonies. Three main theories explain cooperation among conspecifics: mutual benefit, kin selection and manipulation. Lifetime reproductive success calculations revealed that mutual benefit does not explain social behaviour in this group as social colonies have lower per capita life time reproductive success than solitary nests. Genetic pedigrees constructed from allozyme data indicate that kin selection might contribute to the maintenance of social nesting -, as social colonies consist of full sisters and thus some indirect fitness benefits are inherently bestowed on subordinate females as a result of remaining to help their dominant sister. These data suggest that the origin of sociality in ceratinines has principal costs and the great ecological success of highly eusociallineages occurred well after social origins. Ecological constraints such as resource limitation, unfavourable weather conditions and parasite pressure have long been considered some of the most important selective pressures for the evolution of sociality. I assessed the fitness consequences of these three ecological factors for reproductive success of solitary and social colonies and found that nest sites were not limiting, and the frequency of social nesting was consistent across brood rearing seasons. Local weather varied between seasons but was not correlated with reproductive success. Severe parasitism resulted in low reproductive success and total nest failure in solitary nests. Social colonies had higher reproductive success and were never extirpated by parasites. I suggest that social nesting represents a form of bet-hedging. The high frequency of solitary nests suggests that this is the optimal strategy when parasite pressure is low. However, social colonies have a selective advantage over solitary nesting females during periods of extreme parasite pressure. Finally, the small carpenter bees are recorded from all continents except Antarctica. I constructed the first molecular phylogeny of ceratinine bees based on four gene regions of selected species covering representatives from all continents and ecological regions. Maximum parsimony and Bayesian Inference tree topology and fossil dating support an African origin followed by an Old World invasion and New World radiation. All known Old World ceratinines form social colonies while New World species are largely solitary; thus geography and phylogenetic inertia are likely predictors of social evolution in this genus. This integrative approach not only describes the behaviour of several previously unknown or little-known Ceratina species, bu~ highlights the fact that this is an important, though previously unrecognized, model for studying evolutionary transitions from solitary to social behaviour.

A study of the polycomb group complexes in the maintenance of heterochromatic genome stability and Alzheimer's disease.

La démence d'Alzheimer est une maladie neurodégénérative caractérisée par une perte progressive et irreversible des fonctions cognitives et des compétences intellectuelles. La maladie d’Alzheimer se présente sous deux formes: la forme familiale ou précoce (EOAD) qui représente 5% des cas et elle est liée à des mutations génétiques affectant le métabolisme des peptides amyloïde; et la forme tardive ou sporadique (LOAD) qui représente 95% des cas mais son étiologie est encore mal définie. Cependant, le vieillissement reste le principal facteur de risque pour développer LOAD. Les changements épigénétiques impliquant des modifications des histones jouent un rôle crucial dans les maladies neurodégénératives et le vieillissement lié à l'âge. Des données récentes ont décrit LOAD comme un désordre de l'épigénome et ont associé ce trouble à l'instabilité génomique. Les protéines Polycomb sont des modificateurs épigénétiques qui induisent le remodelage de la chromatine et la répression des gènes à l'hétérochromatine facultative. Nous rapportons que les souris hétérozygotes pour une protéine Polycomb développent avec l'âge un trouble neurologique ressemblant à LOAD caractérisé par l’altération des fonctions cognitives, la phosphorylation de la protéine tau, l'accumulation des peptides amyloïde, et le dysfonctionnement synaptique. Ce phénotype pathologique est précédé par la décondensation de l’hétérochromatine neuronale et l'activation de la réponse aux dommages à l'ADN. Parallèlement, une réduction d’expression de polycomb, malformations de l'hétérochromatine neuronale, et l'accumulation de dommages à l'ADN étaient également présents dans les cerveaux de patients LOAD. Remarquablement, les dommages de l'ADN ne sont pas distribués de façon aléatoire sur le génome mais sont enrichis au niveau des séquences répétitives. Les conclusions présentées dans cette thèse ont identifié des modifications épigénétiques spécifiques qui conduisent à une instabilité génomique aberrante menant à la formation de LOAD. Ces résultats vont aider au développement de nouveaux traitements qui peuvent potentiellement ralentir la neurodégénérescence.

Facial artery musculomucosal flap for reconstruction of skull base defects

Facial Artery Musculomucosal Flap in Skull Base Reconstruction Xie L. MD, Lavigne F. MD, Rahal A. MD, Moubayed SP MD, Ayad T. MD Introduction: Failure in skull base defects reconstruction can have serious consequences such as meningitis and pneumocephalus. The nasoseptal flap is usually the first choice but alternatives are necessary when this flap is not available. The facial artery musculomucosal (FAMM) flap has proven to be successful in head and neck reconstruction but it has never been reported in skull base reconstruction. Objective: To show that the FAMM flap can reach some key areas of the skull base and be considered as a new alternative in skull base defects reconstruction. Methods: We conducted a cadaveric study with harvest of modified FAMM flaps, endoscopic skull base dissection and maxillectomies in 13 specimens. Measures were taken for each harvested FAMM flap. Results: The approximate mean area for reconstruction from the combination of the distal FAMM and the extension flaps is 15.90 cm2. The flaps successfully covered the simulated defects of the frontal sinus, the ethmoid areas, the planum sphenoidale, and the sella turcica. Conclusion: The FAMM flap can be considered as a new alternative in the reconstruction of skull base defects. Modifications add extra length to the traditional FAMM flap and can contribute to a tighter seal of the defect as opposed to the FAMM flap alone.

Ruthenium complexes of Schiff base ligands as efficient catalysts for catechol–hydrogen peroxide reaction

Zeolite Y-encapsulated ruthenium(III) complexes of Schiff bases derived from 3-hydroxyquinoxaline-2-carboxaldehyde and 1,2- phenylenediamine, 2-aminophenol, or 2-aminobenzimidazole (RuYqpd, RuYqap and RuYqab, respectively) and the Schiff bases derived from salicylaldehyde and 1,2-phenylenediamine, 2-aminophenol, or 2-aminobenzimidazole (RuYsalpd, RuYsalap and RuYsalab, respectively) have been prepared and characterized. These complexes, except RuYqpd, catalyze catechol oxidation by H2O2 selectively to 1,2,4-trihydroxybenzene. RuYqpd is inactive. A comparative study of the initial rates and percentage conversion of the reaction was done in all cases. Turn over frequency of the catalysts was also calculated. The catalytic activity of the complexes is in the order RuYqap > RuYqab for quinoxaline-based complexes and RuYsalap > RuYsalpd > RuYsalab for salicylidene-based complexes. The reaction is believed to proceed through the formation of a Ru(V) species.

On-the-Fly Maintenance of Series-Parallel Relationships in Fork-Join Multithreaded Programs

A key capability of data-race detectors is to determine whether one thread executes logically in parallel with another or whether the threads must operate in series. This paper provides two algorithms, one serial and one parallel, to maintain series-parallel (SP) relationships "on the fly" for fork-join multithreaded programs. The serial SP-order algorithm runs in O(1) amortized time per operation. In contrast, the previously best algorithm requires a time per operation that is proportional to Tarjan’s functional inverse of Ackermann’s function. SP-order employs an order-maintenance data structure that allows us to implement a more efficient "English-Hebrew" labeling scheme than was used in earlier race detectors, which immediately yields an improved determinacy-race detector. In particular, any fork-join program running in T₁ time on a single processor can be checked on the fly for determinacy races in O(T₁) time. Corresponding improved bounds can also be obtained for more sophisticated data-race detectors, for example, those that use locks. By combining SP-order with Feng and Leiserson’s serial SP-bags algorithm, we obtain a parallel SP-maintenance algorithm, called SP-hybrid. Suppose that a fork-join program has n threads, T₁ work, and a critical-path length of T[subscript ∞]. When executed on P processors, we prove that SP-hybrid runs in O((T₁/P + PT[subscript ∞]) lg n) expected time. To understand this bound, consider that the original program obtains linear speed-up over a 1-processor execution when P = O(T₁/T[subscript ∞]). In contrast, SP-hybrid obtains linear speed-up when P = O(√T₁/T[subscript ∞]), but the work is increased by a factor of O(lg n).

Probabilistic models to assist maintenance of multiple instruments

The paper discusses maintenance challenges of organisations with a huge number of devices and proposes the use of probabilistic models to assist monitoring and maintenance planning. The proposal assumes connectivity of instruments to report relevant features for monitoring. Also, the existence of enough historical registers with diagnosed breakdowns is required to make probabilistic models reliable and useful for predictive maintenance strategies based on them. Regular Markov models based on estimated failure and repair rates are proposed to calculate the availability of the instruments and Dynamic Bayesian Networks are proposed to model cause-effect relationships to trigger predictive maintenance services based on the influence between observed features and previously documented diagnostics

Self-deception as a mechanism for the maintenance of drug addiction

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Narration for instructional video: operation and maintenance of the Nucleus 22 Channel Cochlear Implant

This paper presents the narration for an educational video on cochlear implants and the implantation process aimed at parents and teachers of hearing-impaired children.

Reduced capacity to sustain positive emotion in major depression reflects diminished maintenance of fronto-striatal brain activation

Anhedonia, the loss of pleasure or interest in previously rewarding stimuli, is a core feature of major depression. While theorists have argued that anhedonia reflects a reduced capacity to experience pleasure, evidence is mixed as to whether anhedonia is caused by a reduction in hedonic capacity. An alternative explanation is that anhedonia is due to the inability to sustain positive affect across time. Using positive images, we used an emotion regulation task to test whether individuals with depression are unable to sustain activation in neural circuits underlying positive affect and reward. While up-regulating positive affect, depressed individuals failed to sustain nucleus accumbens activity over time compared with controls. This decreased capacity was related to individual differences in self-reported positive affect. Connectivity analyses further implicated the fronto-striatal network in anhedonia. These findings support the hypothesis that anhedonia in depressed patients reflects the inability to sustain engagement of structures involved in positive affect and reward.

Assembly and maintenance of the sarcomere night and day

The assembly of sarcomeric proteins into the highly organized structure of the sarcomere is an ordered and complex process involving an array of structural and associated proteins. The sarcomere has shown itself to be considerably more complex than ever envisaged and may be considered one of the most complex macromolecular assemblies in biology. Studies over the last decade have helped to put a new face on the sarcomere, and, as such, the sarcomere is being redefined as a dynamic network of proteins capable of generating force and signalling with other cellular compartments and metabolic enzymes capable of controlling many facets of striated myocyte biology.