Effect of a protective-ventilation strategy on mortality in the acute respiratory distress syndrome

BACKGROUND

In patients with the acute respiratory distress syndrome, massive alveolar collapse and cyclic lung reopening and overdistention during mechanical ventilation may perpetuate alveolar injury. We determined whether a ventilatory strategy designed to minimize such lung injuries could reduce not only pulmonary complications but also mortality at 28 days in patients with the acute respiratory distress syndrome.

METHODS

We randomly assigned 53 patients with early acute respiratory distress syndrome (including 28 described previously), all of whom were receiving identical hemodynamic and general support, to conventional or protective mechanical ventilation. Conventional ventilation was based on the strategy of maintaining the lowest positive end-expiratory pressure (PEEP) for acceptable oxygenation, with a tidal volume of 12 ml per kilogram of body weight and normal arterial carbon dioxide levels (35 to 38 mm Hg). Protective ventilation involved end-expiratory pressures above the lower inflection point on the static pressure-volume curve, a tidal volume of less than 6 ml per kilogram, driving pressures of less than 20 cm of water above the PEEP value, permissive hypercapnia, and preferential use of pressure-limited ventilatory modes.

RESULTS

After 28 days, 11 of 29 patients (38 percent) in the protective-ventilation group had died, as compared with 17 of 24 (71 percent) in the conventional-ventilation group (P<0.001). The rates of weaning from mechanical ventilation were 66 percent in the protective-ventilation group and 29 percent in the conventional-ventilation group (P=0.005): the rates of clinical barotrauma were 7 percent and 42 percent, respectively (P=0.02), despite the use of higher PEEP and mean airway pressures in the protective-ventilation group. The difference in survival to hospital discharge was not significant; 13 of 29 patients (45 percent) in the protective-ventilation group died in the hospital, as compared with 17 of 24 in the conventional-ventilation group (71 percent, P=0.37).

CONCLUSIONS

As compared with conventional ventilation, the protective strategy was associated with improved survival at 28 days, a higher rate of weaning from mechanical ventilation, and a lower rate of barotrauma in patients with the acute respiratory distress syndrome. Protective ventilation was not associated with a higher rate of survival to hospital discharge.

SARS-CoV-2-triggered neutrophil extracellular traps mediate COVID-19 pathology

Severe COVID-19 patients develop acute respiratory distress syndrome that may progress to cytokine storm syndrome, organ dysfunction, and death. Considering that neutrophil extracellular traps (NETs) have been described as important mediators of tissue damage in inflammatory diseases, we investigated whether NETs would be involved in COVID-19 pathophysiology. A cohort of 32 hospitalized patients with a confirmed diagnosis of COVID-19 and healthy controls were enrolled. The concentration of NETs was augmented in plasma, tracheal aspirate, and lung autopsies tissues from COVID-19 patients, and their neutrophils released higher levels of NETs. Notably, we found that viable SARS-CoV-2 can directly induce the release of NETs by healthy neutrophils. Mechanistically, NETs triggered by SARS-CoV-2 depend on angiotensin-converting enzyme 2, serine protease, virus replication, and PAD-4. Finally, NETs released by SARS-CoV-2–activated neutrophils promote lung epithelial cell death in vitro. These results unravel a possible detrimental role of NETs in the pathophysiology of COVID-19. Therefore, the inhibition of NETs represents a potential therapeutic target for COVID-19.

Silver colloidal nanoparticles: antifungal effect against adhered cells and biofilms of Candida albicans and Candida glabrata

The aim of this study was to evaluate the effect of silver nanoparticles (SN) against Candida albicans and Candida glabrata adhered cells and biofilms. SN (average diameter 5 nm) were synthesized by silver nitrate reduction with sodium citrate and stabilized with ammonia. Minimal inhibitory concentration (MIC) tests were performed for C. albicans (n = 2) and C. glabrata (n = 2) grown in suspension following the Clinical Laboratory Standards Institute microbroth dilution method. SN were applied to adhered cells (2 h) or biofilms (48 h) and after 24 h of contact their effect was assessed by enumeration of colony forming units (CFUs) and quantification of total biomass (by crystal violet staining). The MIC results showed that SN were fungicidal against all strains tested at very low concentrations (0.4-3.3 μg ml(-1)). Furthermore, SN were more effective in reducing biofilm biomass when applied to adhered cells (2 h) than to pre-formed biofilms (48 h), with the exception of C. glabrata ATCC, which in both cases showed a reduction ∼90%. Regarding cell viability, SN were highly effective on adhered C. glabrata and respective biofilms. On C. albicans the effect was not so evident but there was also a reduction in the number of viable biofilm cells. In summary, SN may have the potential to be an effective alternative to conventional antifungal agents for future therapies in Candida-associated denture stomatitis.

Interference in adhesion of bacteria and yeasts isolated from explanted voice prostheses to silicone rubber by rhamnolipid biosurfactants

AIMS

The effects and extent of adhesion of four different bacterial and two yeast strains isolated from explanted voice prostheses to silicone rubber with and without an adsorbed rhamnolipid biosurfactant layer obtained from Pseudomonasaeruginosa DS10-129 was studied.

METHODS AND RESULTS

The ability of rhamnolipid biosurfactant to inhibit adhesion of micro-organisms to silicone rubber was investigated in a parallel-plate flow chamber. The anti-adhesive activity of the biosurfactant at different concentrations was significant against all the strains and depended on the micro-organism tested. The results showed an effective reduction in the initial deposition rates, and the number of bacterial cells adhering after 4 h, for all micro-organisms tested at the 4 g l(-1) undiluted rhamnolipid solution. Maximum initial reduction of adhesion rate (an average of 66%) occurred for Streptococcus salivarius GB 24/9 and Candida tropicalis GB 9/9. The number of cells adhering after 4 h on silicone rubber conditioned with biosurfactant was reduced to 48% for Staphylococcus epidermidis GB 9/6, Strep. salivarius GB 24/9, Staphylococcus aureus GB 2/1 and C. tropicalis GB 9/9 in comparison to controls. Perfusing the flow chamber with biosurfactant containing solution followed by the passage of a liquid-air interface, to investigate detachment of micro-organisms adhering to silicone rubber, produced high detachment (96%) of adhered cells for all micro-organisms studied, except for Staph. aureus GB 2/1 (67%).

SIGNIFICANCE AND IMPACT OF THE STUDY

It is concluded that biosurfactant represent suitable compounds that should be considered in developing future strategies to prevent the microbial colonization of silicone rubber voice prostheses.

Mitochondrial function is differentially affected upon oxidative stress

The mechanisms that lead to mitochondrial damage under oxidative stress conditions were examined in synaptosomes treated with ascorbate/iron. A loss of membrane integrity, evaluated by electron microscopy and by LDH leakage, was observed in peroxidized synaptosomes and it was prevented by pre-incubation with vitamin E (150 microM) and idebenone (50 microM). ATP levels decreased, in synaptosomes exposed to ascorbate/iron, as compared to controls. NADH-ubiquinone oxidoreductase (Cx I) and cytochrome c oxidase (Cx IV) activities were unchanged after ascorbate/iron treatment, whereas succinate-ubiquinone oxidoreductase (Cx II), ubiquinol cytochrome c reductase (Cx III) and ATP-synthase (Cx V) activities were reduced by 55%, 40%, and 55%, respectively. The decrease of complex II and ATP-synthase activities was prevented by reduced glutathione (GSH), whereas the other antioxidants tested (vitamin E and idebenone) were ineffective. However, vitamin E, idebenone and GSH prevented the reduction of complex III activity observed in synaptosomes treated with ascorbate/iron. GSH protective effect suggests that the oxidation of protein SH-groups is involved in the inhibition of complexes II, III and V activity, whereas vitamin E and idebenone protection suggests that membrane lipid peroxidation is also involved in the reduction of complex III activity. These results may indicate that the inhibition of the mitochondrial respiratory chain enzymatic complexes, that are differentially affected by oxidative stress, can be recovered by specific antioxidants.

Susceptibility of Staphylococcus epidermidis planktonic cells and biofilms to the lytic action of staphylococcus bacteriophage K

AIMS

To evaluate differences in biofilm or planktonic bacteria susceptibility to be killed by the polyvalent antistaphylococcus bacteriophage K.

METHODS AND RESULTS

In this study, the ability of phage K to infect and kill several clinical isolates of Staphylococcus epidermidis was tested. Strains were grown in suspension or as biofilms to compare the susceptibility of both phenotypes to the phage lytic action. Most strains (10/11) were susceptible to phage K, and phage K was also effective in reducing biofilm biomass after 24 h of challenging. Biofilm cells were killed at a lower rate than the log-phase planktonic bacteria but at similar rate as stationary phase planktonic bacteria.

CONCLUSIONS

Staphylococcus epidermidis biofilms and stationary growth phase planktonic bacteria are more resistant to phage K lysis than the exponential phase planktonic bacteria. SIGNIFICANCE OF STUDY: This study shows the differences in Staph. epidermidis susceptibility to be killed by bacteriophage K, when grown in biofilm or planktonic phenotypes.

Do oral biofilms influence the wear and corrosion behavior of titanium?

The main aim of this work was to study the simultaneous wear-corrosion of titanium (Ti) in the presence of biofilms composed of Streptococcus mutans and Candida albicans. Both organisms were separately grown in specific growth media, and then mixed in a medium supplemented with a high sucrose concentration. Corrosion and tribocorrosion tests were performed after 48 h and 216 h of biofilm growth. Electrochemical corrosion tests indicated a decrease in the corrosion resistance of Ti in the presence of the biofilms although the TiO(2) film presented the characteristics of a compact oxide film. While the open circuit potential of Ti indicated a tendency to corrosion in the presence of the biofilms, tribocorrosion tests revealed a low friction on biofilm covered Ti. The properties of the biofilms were similar to those of the lubricant agents used to decrease the wear rate of materials. However, the pH-lowering promoted by microbial species, can lead to corrosion of Ti-based oral rehabilitation systems.

Insights into Candida tropicalis nosocomial infections and virulence factors

Candida tropicalis is considered the first or the second non-Candida albicans Candida (NCAC) species most frequently isolated from candidosis, mainly in patients admitted in intensive care units (ICUs), especially with cancer, requiring prolonged catheterization, or receiving broad-spectrum antibiotics. The proportion of candiduria and candidemia caused by C. tropicalis varies widely with geographical area and patient group. Actually, in certain countries, C. tropicalis is more prevalent, even compared with C. albicans or other NCAC species. Although prophylactic treatments with fluconazole cause a decrease in the frequency of candidosis caused by C. tropicalis, it is increasingly showing a moderate level of fluconazole resistance. The propensity of C. tropicalis for dissemination and the high mortality associated with its infections might be strongly related to the potential of virulence factors exhibited by this species, such as adhesion to different host surfaces, biofilm formation, infection and dissemination, and enzymes secretion. Therefore, the aim of this review is to outline the present knowledge on all the above-mentioned C. tropicalis virulence traits.

GUP1 and its close homologue GUP2, encoding multimembrane-spanning proteins involved in active glycerol uptake in Saccharomyces cerevisiae

Many yeast species can utilize glycerol, both as a sole carbon source and as an osmolyte. In Saccharomyces cerevisiae, physiological studies have previously shown the presence of an active uptake system driven by electrogenic proton symport. We have used transposon mutagenesis to isolate mutants affected in the transport of glycerol into the cell. Here we present the identification of YGL084c, encoding a multimembrane-spanning protein, as being essential for proton symport of glycerol into S. cerevisiae. The gene is named GUP1 (glycerol uptake) and, for growth on glycerol, is important as a carbon and energy source. In addition, in strains deficient in glycerol production it also provides osmotic protection by the addition of glycerol. Another open reading frame (ORF), YPL189w, presenting a high degree of homology to YGL084c, similarly appears to be involved in active glycerol uptake in salt-containing glucose-based media in strains deficient in glycerol production. Analogously, this gene is named GUP2. To our knowledge, this is the first report on a gene product involved in active transport of glycerol in yeasts. Mutations with the same phenotypes occurred in two other ORFs of previously unknown function, YDL074c and YPL180w.

Silver nanoparticles: influence of stabilizing agent and diameter on antifungal activity against Candida albicans and Candida glabrata biofilms

AIM

  The purpose of this work was to evaluate the size-dependent antifungal activity of different silver nanoparticles (SN) colloidal suspensions against Candida albicans and Candida glabrata mature biofilms.

METHODS AND RESULTS

  The research presented herein used SN of three different average sizes (5, 10 and 60 nm), which were synthesized by the reduction of silver nitrate through sodium citrate and which were stabilized with ammonia or polyvinylpyrrolidone. Minimal inhibitory concentration (MIC) assays were performed using the microdilution methodology. The antibiofilm activity of SN was determined by total biomass quantification (by crystal violet staining) and colony forming units enumeration. MIC results showed that all SN colloidal suspensions were fungicidal against the tested strains at very low concentrations (0·4-3·3 μg ml(-1) ). With regard to biomass quantification, SN colloidal suspensions were very effective only against C. glabrata biofilms, achieving biomass reductions around 90% at a silver concentration of 108 μg ml(-1) . In general, all SN suspensions promoted significant log(10) reduction of the mean number of cultivable biofilm cells after exposure to silver concentrations at or higher than 108 μg ml(-1) . Moreover, the results showed that the particle size and the type of stabilizing agent used did not interfere in the antifungal activity of SN against Candida biofilms.

CONCLUSIONS

  This study suggests that SN have antifungal therapeutic potential, but further studies are still required namely regarding formulation and delivery means.

SIGNIFICANCE AND IMPACT OF THE STUDY

  SN may contribute to the development of new strategies for the improvement of oral health and quality of life particularly of the complete denture wearers.

Mini-review: Staphylococcus epidermidis as the most frequent cause of nosocomial infections: old and new fighting strategies

Staphylococcus epidermidis is nowadays regarded as the most frequent cause of nosocomial infections and indwelling medical device-associated infections. One of the features that contributes to the success of this microorganism and which is elemental to the onset of pathogenesis is its ability to form biofilms. Cells in this mode of growth are inherently more resistant to antimicrobials. Seeking to treat staphylococcal-related infections and to prevent their side effects, such as the significant morbidity and health care costs, many efforts are being made to develop of new and effective antistaphylococcal drugs. Indeed, due to its frequency and extreme resistance to treatment, staphylococcal-associated infections represent a serious burden for the public health system. This review will provide an overview of some conventional and emerging anti-biofilm approaches in the management of medical device-associated infections related to this important nosocomial pathogen.

Silver colloidal nanoparticles: effect on matrix composition and structure of Candida albicans and Candida glabrata biofilms

AIM

The aim of this study was to assess the effect of different silver nanoparticles (SN) concentrations on the matrix composition and structure of Candida albicans and Candida glabrata biofilms.

METHODS AND RESULTS

Candida biofilms were developed in 6-well microtiter plates during 48 h. After, these biofilms were exposed to 13.5 or 54 μg SN ml(-1) for 24 h. Then, extracellular matrices were extracted from biofilms and analysed chemically in terms of proteins, carbohydrates and DNA. To investigate the biofilm structure, scanning electron microscopy (SEM) and epifluorescence microscopy were used. SN interfered with the matrix composition of Candida biofilms tested in terms of protein, carbohydrate and DNA, except for the protein content of C. albicans biofilm. By SEM, Candida biofilms treated with SN revealed structural differences, when compared with the control groups. Further, SN showed a trend of agglomeration within the biofilms. Epifluorescence microscopy images suggest that SN induced damage on cell walls of the Candida isolates tested.

CONCLUSIONS

In general, irrespective of concentration, SN affected the matrix composition and structure of Candida biofilms and these findings may be related to the mechanisms of biocide action of SN.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study reveals new insights about the behaviour of SN when in contact with Candida biofilms. SN may contribute to the development of therapies to prevent or control Candida infections.

Effects of ivermectin on Danio rerio: a multiple endpoint approach: behaviour, weight and subcellular markers

Ivermectin (IVM) is a broad acting antihelmintic used in various veterinary pharmaceuticals. It has been shown that IVM enters the aquatic compartment and adversely affects organisms including fish. This study is based on the hypothesis that long term exposure to IVM affects fish and thus, the main objective was to assess the chronic effects of 0.25 and 25 µg IVM/L to zebrafish using multiple endpoints representative of several levels of biological organization: weight, behaviour (swimming and feeding) and subcellular markers including biomarkers for oestrogenicity (vitellogenin-VTG), oxidative stress (catalase-CAT and glutathione-S-transferase-GST) and neurotransmission (cholinesterase-ChE). Concentrations as low as 0.25 µg IVM/L disrupted the swimming behaviour, causing fish to spend more time at the bottom of aquaria. Such reduction of the swimming performance affected the feeding ability which is likely responsible for the weight loss. The effects on weight were gender differentiated, being more pronounced in males (0.25 µg IVM/L) than in females (25 µg IVM/L). Fish exposed to 25 µg/L exhibited darker coloration and mild curvature of the spine. No effects on VTG and AChE were observed, but a reduction on CAT and GST levels was observed in fish exposed to 25 µg IVM/L, although these alterations probably only reflect the general condition of the fish which was significantly compromised at this concentration. Despite that predicted environmental concentrations of IVM are below 0.25 µg/L, the behavioural effects may be translated into important ecological impacts, e.g. at predator-prey interactions where fish competitive advantage can be decreased. Future work should address the link between behaviour disruption and population fitness. The current study was based on a one experiment and multiple endpoint (anchored) approach, allowing the results to be integrated and linked towards a mechanistic understanding.

Influence of composition on the biomethanation potential of restaurant waste at mesophilic temperatures

A synthetic waste was used to study the effect of waste composition on anaerobic degradation of restaurant waste. It was made by blending melted pork lard, white cabbage, chicken breast, and potato flakes, to simulate lipids, cellulose, protein, and carbohydrates, respectively. Four blends of the four constituents with an excess of each component were assayed and compared with a fifth blend containing an equal amount of chemical oxygen demand (COD) of each of the four components. The methane production and the time course of soluble COD and volatile fatty acids were assessed in batch assays. A high reduction of volatile solids (between 94% and 99.6%) was obtained in all the assays. The methane yield was between 0.40 m(3) CH(4)/kg VS(initial) (excess of carbohydrates) and 0.49 m(3) CH(4)/kg VS(initial) (excess of lipids). The degradation of the lipid-rich assays differed from the others. Fifty percent of the biochemical methane potential was obtained after 3-6 days for all of the assays, except for the one with excess of lipids which achieved 50% methanation only after 14.7 days of incubation. In the assay with excess of lipids, a considerable fraction of COD remained in the liquid phase, suggesting an inhibition of the methanogenic process that was likely due to the accumulation of long chain fatty acids. The hydrolysis rate constants, assuming first order kinetics, over the first 6 days were between 0.12d(-1) (excess of lipids) and 0.32 d(-1) (excess of carbohydrates). The results indicate that anaerobic digestion facilities with large variations in lipid input could have significant changes in process performance that merit further examination.

Effect of increasing amounts of supplemental progesterone in a timed artificial insemination protocol on fertility of lactating dairy cows

The objectives were to evaluate the effect of supplemental progesterone during a timed artificial insemination (TAI) protocol on pregnancy per insemination and pregnancy loss. Lactating dairy cows from 2 dairy herds were presynchronized with 2 injections of PGF(2alpha) 14 d apart, and cows observed in estrus following the second PGF(2alpha) injection were inseminated (n = 1,301). Cows not inseminated by 11 d after the end of the presynchronization were submitted to the TAI protocol (d 0 GnRH, d 7 PGF(2alpha), d 8 estradiol cypionate, and d 10 TAI). On the day of the GnRH of the TAI protocol (study d 0), cows were assigned randomly to receive no exogenous progesterone (control = 432), one controlled internal drug-release (CIDR) insert (CIDR1 = 440), or 2 CIDR inserts (CIDR2 = 440) containing 1.38 g of progesterone each from study d 0 to 7. Blood was sampled on study d 0 before insertion of CIDR for determination of progesterone concentration in plasma, and cows with concentration <1.0 ng/mL were classified as low progesterone (LP) and those with concentration > or =1.0 ng/mL were classified as high progesterone (HP). From a subgroup of 240 cows, blood was sampled on study d 3, 7, 17 and 24 and ovaries were examined by ultrasonography on study d 0 and 7. Pregnancy was diagnosed at 38 +/- 3 and 66 +/- 3 d after AI. Data were analyzed including only cows randomly assigned to treatments and excluding cows that were inseminated after the second PGF(2alpha) injection. The proportion of cows classified as HP at the beginning of the TAI protocol was similar among treatments, but differed between herds. Concentrations of progesterone in plasma during the TAI protocol increased linearly with number of CIDR used, and the increment was 0.9 ng/mL per CIDR. The proportion of cows with plasma progesterone > or =1.0 ng/mL on study d 17 was not affected by treatment, but a greater proportion of control than CIDR-treated cows had asynchronous estrous cycles following the TAI protocol. Treatment with CIDR inserts, however, did not affect pregnancy at 38 +/- 3 and 66 +/- 3 d after AI or pregnancy loss.

Toward a genome-wide approach for detecting hybrids: informative SNPs to detect introgression between domestic cats and European wildcats (Felis silvestris)

Endemic gene pools have been severely endangered by human-mediated hybridization, which is posing new challenges in the conservation of several vertebrate species. The endangered European wildcat is an example of this problem, as several natural populations are suffering introgression of genes from the domestic cat. The implementation of molecular methods for detecting hybridization is crucial for supporting appropriate conservation programs on the wildcat. In this study, genetic variation at 158 single-nucleotide polymorphisms (SNPs) was analyzed in 139 domestic cats, 130 putative European wildcats and 5 captive-bred hybrids (N=274). These SNPs were variable both in wild (HE=0.107) and domestic cats (HE=0.340). Although we did not find any SNP that was private in any population, 22 SNPs were monomorphic in wildcats and pairwise FCT values revealed marked differences between domestic and wildcats, with the most divergent 35 loci providing an average FCT>0.74. The power of all the loci to accurately identify admixture events and discriminate the different hybrid categories was evaluated. Results from simulated and real genotypes show that the 158 SNPs provide successful estimates of admixture, with 100% hybrid individuals (two to three generations in the past) being correctly identified in STRUCTURE and over 92% using the NEWHYBRIDS' algorithm. None of the unclassified cats were wrongly allocated to another hybrid class. Thirty-five SNPs, showing the highest FCT values, provided the most parsimonious panel for robust inferences of parental and first generations of admixed ancestries. This approach may be used to further reconstruct the evolution of wildcat populations and, hopefully, to develop sound conservation guidelines for its legal protection in Europe.

The role of secreted aspartyl proteinases in Candida tropicalis invasion and damage of oral mucosa

Candida virulence attributes include the ability to colonize and invade host tissues, and the secretion of hydrolytic enzymes. Although Candida albicans is regarded as the principal fungi causing infections in humans, other species, particularly Candida tropicalis, are increasingly being recognized as human pathogens. Relatively little is known, however, about the virulence attributes associated with C. tropicalis. The present study aimed to investigate epithelial infection by C. tropicalis using a reconstituted human oral epithelium (RHOE) together with confocal laser scanning microscopy and real-time PCR. A comparison of clinical strains was made in terms of tissue colonization, invasion and C. tropicalis secreted aspartyl proteinase (SAPT) gene expression. All C. tropicalis strains were able to colonize RHOE in a strain-dependent manner. After 12 h of infection, C. tropicalis was found to be highly invasive, with extensive tissue damage occurring after 24 h. Real-time PCR of C. tropicalis SAPT1-4 genes showed that expression was strain-dependent, with SAPT2-4 transcripts being frequently detected and SAPT1 rarely detected. Tissue invasion and damage was not inhibited by the presence of pepstatin A. Accordingly, and given that an increase in infection time was not accompanied with an increase in SAPT gene expression, it can be suggested that the proteinases are not involved in invasion and damage of RHOE by C. tropicalis. In summary, C. tropicalis can be considered as highly invasive with the ability to induce significant tissue damage. These features, however, do not appear to be related to specific SAPT gene expression.

Benefits and risks associated with consumption of raw, cooked, and canned tuna (Thunnus spp.) based on the bioaccessibility of selenium and methylmercury

The Se, Hg, and methylmercury (MeHg) levels in raw, cooked (boiled and grilled), and canned tuna (Thunnus spp.) were determined before and after an in vitro digestion, thereby enabling the calculation of the respective bioaccessibility percentages. A risk-benefit evaluation of raw and canned tuna on the basis of the Se and MeHg data was performed. Selenium bioaccessibility was high in tuna, though slightly lower in canned than in raw products. Mercury levels were high in raw and cooked tuna. Hg bioaccessibility percentages were low (39-48%) in the cooked tuna and even lower (<20%) in canned tuna. For the bioaccessible fraction, all molar Se:MeHg ratios were higher than one (between 10 and 74). A probabilistic assessment of MeHg risk vs Se benefit showed that while a weekly meal of canned tuna presents very low risk, raw, boiled, and grilled tuna consumption should not exceed a monthly meal, at least, for pregnant and nursing women.

Cardiorespiratory responses of the facultative air-breathing fish jeju, Hoplerythrinus unitaeniatus (Teleostei, Erythrinidae), exposed to graded ambient hypoxia

The jeju, Hoplerythrinus unitaeniatus, is equipped with a modified part of the swim bladder that allows aerial respiration. On this background, we have evaluated its respiratory and cardiovascular responses to aquatic hypoxia. Its aquatic O2 uptake (V(O2)) was maintained constant down to a critical P(O2) (P(cO2)) of 40 mm Hg, below which V(O2) declined linearly with further reductions of P(iO2). Just below P(cO2), the ventilatory tidal volume (V(T)) increased significantly along with gill ventilation (V(G)), while respiratory frequency changed little. Consequently, water convection requirement (V(G)/V(O2)) increased steeply. The same threshold applied to cardiovascular responses that included reflex bradycardia and elevated arterial blood pressure (P(a)). Aerial respiration was initiated at water P(O2) of 44 mm Hg and breathing episodes and time at the surface increased linearly with more severe hypoxia. At the lowest water P(O2) (20 mm Hg), the time spent at the surface accounted for 50% of total time. This response has a character of a temporary emergency behavior that may allow the animal to escape hypoxia.

Co-digestion of cow manure, food waste and intermittent input of fat

Pulses of oil were added to completely mixed reactors fed with dairy cow manure and food waste, after achieving a stable performance at an organic loading rate of 4.6+/-0.1gCOD/(l(reactor) day), an oily waste effluent from a canned fish processing industry was fed in the form of pulses. The oil concentration rose up to 9, 12, 15 and 18gCOD(oil)/l(reactor,) after the pulse feeding in the reactor. The highest fat concentration of 18gCOD(oil)/l(reactor) promoted a persistent inhibition in the process of the continuous reactor, although in batch assays, the reactor content evidenced a capacity to degrade more oil and to degrade the accumulated organic matter. All the other pulses had a positive effect in the methane production. From a practical point of view, this work demonstrates that controlled intermittent inputs of oil can enhance the methane production in a co-digestion of cow manure and food waste.

Candida albicans and Candida dubliniensis: comparison of biofilm formation in terms of biomass and activity

Candida albicans and C. dubliniensis are two species responsible for oral candidiasis, especially in immunocompromised patients. Microbial infection is preceded by adherence and biofilm formation. Biofilm formation represents the most common form of C. albicans in the oral cavity and is considered to be one of the most important virulence factors. In this study, the biofilm formation ability of C. dubliniensis was compared with that of C. albicans in terms of biomass (quantified using crystal violet) and activity (assessed by formazan salts formation). Both species formed heterogeneous biofilms; however, species and strain variations were seen in the quantification of biomass and activity. There was no correlation between pseudohyphae formation and biofilm formation capability.

Free radical-mediated pre-hemolytic injury in human red blood cells subjected to lead acetate as evaluated by chemiluminescence

The mechanisms by which Pb(2+) induces hemolysis are not completely understood. For this reason, the involvement of oxidative stress in the mechanism of Pb(2+)-induced pre-hemolytic lesion was investigated by exposing RBC to Pb(2+) in vitro and then separating the intact non-hemolysed RBC. Oxidative stress was investigated on human RBCs by tert-butyl hydroperoxide-initiated chemiluminescence method (CL). Our results revealed that lead-induced time and concentration-dependent hemolysis and CL time curves showed a very narrow correlation each other. GSH oxidation to GSSG and the stress index also increased significantly. Treatment of lead-exposed RBC with desferrioxamine, an iron-chelating agent or the chain-breaking antioxidant, Trolox, quenched light emission and inhibited hemolysis dramatically. Mannitol and sodium formate, (*)OH scavengers, on the contrary, did not inhibit CL or hemolysis, significantly. These data indicate that lead-induced lipid peroxide formation is mediated by a metal-driven Fenton reaction but do not support the direct involvement of hydroxyl radicals in this process. By contrast, our results revealed a decrease in light emission and decreased hemolysis in the presence of histidine, a singlet oxygen scavenger. Our results suggest that membrane damage and hemolysis of RBC are mediated by Pb(2+) through free radical reactions and that singlet oxygen plays a significant role in this process.

Modelling and optimization of a recombinant BHK-21 cultivation process using hybrid grey-box systems

In this work a model-based optimization study of fed-batch BHK-21 cultures expressing the human fusion glycoprotein IgG1-IL2 was performed. It was concluded that due to the complexity of the BHK metabolism it is rather difficult to develop a kinetic model with sufficient accuracy for optimization studies. Many kinetic expressions and a large number of parameters are involved resulting in a complex identification problem. For this reason, an alternative more cost-effective methodology based on hybrid grey-box models was adopted. Several model structures combining the a priori reliable first principles knowledge with black-box models were investigated using data from batch and fed-batch experiments. It has been reported in previous studies that the BHK metabolism exhibits modulation particularities when compared to other mammalian cell lines. It was concluded that these mechanisms were effectively captured by the hybrid model, this being of crucial importance for the successful optimization of the process operation. A method was proposed to monitor the risk of hybrid model unreliability and to constraint the optimization results to acceptable risk levels. From the optimization study it was concluded that the process productivity may be considerably increased if the glutamine and glucose concentrations are maintained at low levels during the growth phase and then glutamine feeding is increased.

Modeling rotavirus-like particles production in a baculovirus expression vector system: Infection kinetics, baculovirus DNA replication, mRNA synthesis and protein production

Rotavirus is the most common cause of severe diarrhoea in children worldwide, responsible for more than half a million deaths in children per year. Rotavirus-like particles (Rota VLPs) are excellent vaccine candidates against rotavirus infection, since they are non-infectious, highly immunogenic, amenable to large-scale production and safer to produce than those based on attenuated viruses. This work focuses on the analysis and modeling of the major events taking place inside Spodoptera frugiperda (Sf-9) cells infected by recombinant baculovirus that may be critical for the expression of rotavirus viral proteins (VPs). For model validation, experiments were performed adopting either a co-infection strategy, using three monocistronic recombinant baculovirus each one coding for viral proteins VP(2), VP(6) and VP(7), or single-infection strategies using a multigene baculovirus coding for the three proteins of interest. A characteristic viral DNA (vDNA) replication rate of 0.19+/-0.01 h(-1) was obtained irrespective of the monocistronic or multigene vector employed, and synthesis of progeny virus was found to be negligible in comparison to intracellular vDNA concentrations. The timeframe for vDNA, mRNA and VP synthesis tends to decrease with increasing multiplicity of infection (MOI) due to the metabolic burden effect. The protein synthesis rates could be ranked according to the gene size in the multigene experiments but not in the co-infection experiments. The model exhibits acceptable prediction power of the dynamics of intracellular vDNA replication, mRNA synthesis and VP production for the three proteins involved. This model is intended to be the basis for future Rota VLPs process optimisation and also a means to evaluating different baculovirus constructs for Rota VLPs production.

Correlation of in vitro infiltration with glioma histological type in organotypic brain slices

Diffuse invasion of the brain, an intrinsic property of gliomas, renders these tumours incurable, and is a principal determinant of their spatial and temporal growth. Knowledge of the invasive potential of gliomas is highly desired in order to understand their behaviour in vivo. Comprehensive ex vivo invasion studies including tumours of different histological types and grades are however lacking, mostly because reliable physiological invasion assays have been difficult to establish. Using an organotypic rodent brain slice assay, we evaluated the invasiveness of 42 grade II–IV glioma biopsy specimens, and correlated it with the histological phenotype, the absence or presence of deletions on chromosomes 1p and 19q assessed by fluorescent in situ hybridisation, and proliferation and apoptosis indices assessed by immunocytochemistry. Oligodendroglial tumours with 1p/19q loss were less invasive than astrocytic tumours of similar tumour grade. Correlation analysis of invasiveness cell proliferation and apoptosis further suggested that grade II–III oligodendroglial tumours with 1p/19q loss grow in situ as relatively circumscribed compact masses in contrast to the more infiltrative and more diffuse astrocytomas. Lower invasiveness may be an important characteristic of oligodendroglial tumours, adding to our understanding of their more indolent clinical evolution and responsiveness to therapy.