Neutral Fraction Research Articles

Lipid production by Rhodosporidium toruloides from biodiesel-derived glycerol in shake flasks and bioreactor: Impact of initial C/N molar ratio and added onion-peel extract

Rhodosporidium toruloides NRRL Y-27012 grown in glycerol, produced yeast biomass and secondary metabolites as lipids (L) and intra-cellular polysaccharides (IPS) in trials under nitrogen limitation (initial C/N molar ratios ≈ 50, ≈ 100, ≈ 160 and ≈ 240). The initial glycerol (Glol0) concentration for all experiments was ≈ 90 g/L. The yeast demonstrated significant dry cell weight (DCW) production irrespective of the C/N ratio employed, ranging between 19 and 29 g/L. The optimum C/N ratio medium was that of 100 moles/moles, where a DCWmax = 24.5 g/L containing c. 50% w/w of lipids was recorded. Endopolysaccharides presented indeed impressive values (≥ 50% w/w) even at the very early growth steps, while IPS/DCW values decreased as the fermentation proceeded, with simultaneous increase of L/DCW values. Experiments were also conducted in media with a hydroglycerolic extract of onion peels (at 40 mL/L), while a blank experiment (no extract) was also realized. The trial with the added extract was performed under both aseptic (previous sterilization) and non-aseptic (previous thermal treatment at T = 100 °C; 5 min) conditions. The aseptic experiment with the added extract resulted in a relative decrease in lipid production in relation to the control (L=8.6 g/L in the control vs L = 6.2 g/L with the extract). Under non-aseptic conditions, lipid production was slightly lower (L = 5.2 g/L). Finally, the optimum trial in shake flasks was scaled-up in a batch bioreactor, and higher glycerol assimilation rate, and biomass and lipid production occurred compared to the flask trial (final DCW and lipid values ≈27 g/L and 13.5 g/L respectively). Cellular lipids, rich in palmitic and oleic acid, were mainly composed of neutral fractions. Phospholipids were more saturated than the neutral lipids.

An alternative method for the separation and analysis of acidic biomarkers from crude oil samples

This study aimed to develop and/or optimize a method of separation and analysis of neutral and acidic constituents from oil samples from Brazilian sedimentary basins and make a broad characterization of these samples through the respective molecular fossils. Three oil samples (A, B and C) of different origins and biodegradation were analyzed in this work. The neutral fractions were subjected to classic separation processes using gradient elution and analyzed by gas chromatography–mass spectrometry (GC–MS). The acidic fraction was isolated using KOH modified silica as stationary, adapted in SPE, and analyzed by GC–MS as silylated derivatives. The molecular parameters for B oil suggest a marine evaporitic depositional environment, with less continental influence, low siliciclastic sediments input, low oxygenation, hypersaline, stratified water column, and persistent photic zone euxinic. For the A and C oils, the parameters indicate a significant similarity between the samples, differing essentially only in the absence of acyclic n-alkanes and isoprenoids because of different stages of biodegradation. The presence of TPP and β-carotane in samples A and C allows us to classify them as mixed origin, with characteristics of lacustrine freshwater and saline depositional environments. Biomarkers associated with dinoflagellates of marine origin in the saturated fraction (dinosteranes) and the aromatic fraction (triaromatic dinosteranes) were detected in all three samples and suggest dinoflagellates were important primary producers during deposition time. 25-Norhopanes were detected only at low concentrations, and biomarker-based geochemical parameters indicate the biodegradation did not change the distribution of steranes and hopanes. The 25-Norhopanoic acids detection also agree with the detection of 25-norhopanes in the A and C oils, supports the same order of biodegradation, C > A ≫ B. The low abundance of tricyclic terpanoic acids in oil B acidic fraction agrees with the low abundance of tricyclic terpanes into the corresponding neutral fraction. Unlike hopanes, hopanoic acids distribution shows the ββ-isomers, biologically and thermally less stable configuration. Especially in oil B, series of 3-carboxysteranes, 3-carboxymethylsteranes were observed. In summary, acidic fractions data from three samples indicate that acidic biomarkers provide parallel information and complementary to that obtained from the hydrocarbon biomarkers. The extraction methods, derivatization and analysis of carboxylic acids from oil samples proved to be efficient, leading to quantitative recoveries and good yields.

Jellyfish Polysaccharides for Wound Healing Applications.

Jellyfishes are considered a new potential resource in food, pharmaceutical and biomedical industries. In these latter cases, they are studied as source of active principles but are also exploited to produce marine collagen. In the present work, jellyfish skin polysaccharides (JSP) with glycosaminoglycan (GAG) features were extracted from Rhizostoma pulmo, a main blooming species of Mediterranean Sea, massively augmented by climate leaded “jellyfishication” of the sea. Two main fractions of R. pulmo JSP (RP-JSPs) were isolated and characterized, namely a neutral fraction (RP-JSP1) and a sulphate rich, negatively charged fraction (RP-JSP2). The two fractions have average molecular weights of 121 kDa and 590 kDa, respectively. Their sugar composition was evaluated through LC-MS analysis and the result confirmed the presence of typical GAG saccharides, such as glucose, galactose, glucosamine and galactosamine. Their use as promoters of wound healing was evaluated through in vitro scratch assay on murine fibroblast cell line (BALB/3T3 clone A31) and human keratinocytes (HaCaT). Both RP-JSPs demonstrated an effective confluency rate activity leading to 80% of scratch repair in two days, promoting both cell migration and proliferation. Additionally, RP-JSPs exerted a substantial protection from oxidative stress, resulting in improved viability of treated fibroblasts exposed to H2O2. The isolated GAG-like polysaccharides appear promising as functional component for biomedical skin treatments, as well as for future exploitation as pharmaceutical excipients.

PSVIII-19 Predict Indigestible Fiber Fraction of Barley Plant Silage by Using non-Destructive Mid-IR vs Near-IR Spectroscopic Techniques

Abstract The objective of this study was to reveal the potential of using Fourier transform mid-infrared (FTIR) and near infrared (NIR) spectroscopy as tools for the determination of indigestible neutral (NDF) fraction (iNDF) of barley plant silage. A total of 48 barley plant silage samples collected from different farms in Western Canada provinces were analyzed for iNDF. Reference values were matched with NIR and FTIR spectra. Spectral data processing (pretreatments) included first derivative (FD), standard normal variate (SNV), multiplicative scattering correction (MSC), second derivative (SD) and orthogonal signal correction (OSC). Prediction equations were obtained from each model using an external validation set. The determination coefficient of external validation (R2P) of iNDF was 0.62 for FTIR, while 0.41 for NIR and the corresponding ratio performance deviation (RPD) were 1.69 and 1.38 in FTIR and NIR, respectively. Results from this research showed the high potential of applying infrared molecular spectroscopy for the examination of forage plant fiber digestibility. More studies are needed to improve the accuracy and performance of FTIR and NIR spectroscopies in predicting the iNDF of barley plant silage samples.

Benefits of neutral polysaccharide from rhizomes of Polygonatum sibiricum to intestinal function of aged mice.

One purified neutral polysaccharide fraction was obtained from the rhizome of Polygonatum sibiricum by DEAE ion exchange and gel chromatography. Structure elucidation was performed by methanolysis, methylation, FT-IR, and NMR. The results indicated that PSP-NP was composed of 1,4-β-D-Gal,1, 4, 6-β-D-Gal, T-α-D-Man,1, 4-α-D-Glc, and T-α-D-Glc with a molecular weight of 43.0 kDa. We supplied this polysaccharide to aged mice and found it is of benefits to intestinal functions, as indicated by better tissue integrity and motility, improved oxidative stress and inflammation, reduced intestinal permeability and serum LPS level, as well as balanced gut microbial composition and short-chain fatty acids production. These results display a novel Polygonatum sibiricum polysaccharide to improve the intestinal function of aged mice, which provides pieces of evidence for its further development and utilization.

Efficient method for the determination of the neutral lipid content of oil-producing microalgae strains required for biodiesel

The continued use of petroleum-derived fuels is unsustainable, as these fuels contribute to the environmental accumulation of carbon dioxide. Renewable fuels are necessary for environmental and economic sustainability. Microalgae appear to be the source of renewable biofuel that can meet the global demand for transport fuels. Like plants, microalgae use sunlight to produce oils but they do so more efficiently than crop plants. Oil productivity of many microalgae greatly exceeds the oil productivity of the best producing oil crops. Using microalgae to produce biofuel does not occupy agricultural land will not compromise production of food and other products derived from crops.During the growth of microalgae, the quantitative and qualitative values of produced lipids are constantly changing. Therefore, a laboratory lipid determination method had to be developed. Among the various industrial lipid extraction and purification methods, we only dealt with methods that can also be used in the laboratory. Because only neutral lipid fraction can be used to produce biofuels, an optimized method had to be developed to separate and determine the amount of neutral lipids. Each step was optimized in terms of time, volume, amount of chemical, simplicity and accuracy, these were the main aspects so that the method could be used for a wide range of lipid content and composition. The developed microextraction method enables the examination of a small amount of sample (100 mg) in a small volume (5 mL), in that way many samples can be processed simultaneously. This method saves time, money and chemicals in the laboratory while improving the accuracy of the lipid content determination.

Enhancement of Lipid and Biomass Production in Microalgae Scenedesmus abundans by Microwave Irradiation

Due to the rising depletion of fossil fuels and increased energy demands, human society is looking for clean sustainable energy. Commercially produced algal biodiesel is limited by the expense and difficulty of oil extraction and subsequent biodiesel conversion technologies. Microalgae with high oil content are only alternatives for decreasing fossil fuel supplies, but more work remains to be done to improve the lipid content of microalgae strains. In this study, strain improvement is done using microwave radiation in Scenedesmus abundans to increase the production of triacylglycerol, which is the main source of biodiesel. Microalgal cultures were exposed to varied microwave irradiation over different time periods. Under microwave irradiation, 20-25 mins reaction time seems suitable for the complete in situ transesterification reaction. Microwave heating transesterification has been shown to be more effective for adequate biodiesel yield compared to the conventional transesterification process. Maximum increase of 2.22-fold in biomass, and 2.5-fold in triacylglycerol was observed for microwave irradiation of 25 mins and 20 mins intervals respectively. The percentage of some monounsaturated fatty acids increased in gas chromatographic examination of neutral lipid fractions from total lipids of microwave irradiated samples, is considered as one of the preferable properties of biodiesel. According to our study findings, Scenedesmus abundans qualifies as the most efficient feedstock for biodiesel production, and microwave-assisted in situ transesterification reduces the requirement for a large amount of solvents, longer reaction times, and high reaction temperatures and pressures.

Enzymatic bioconversion of beechwood xylan into the antioxidant 2′-O-α-(4-O-methyl-D-glucuronosyl)-xylobiose

Acidic xylooligosaccharides (XOS), also called aldouronics, are hetero-oligomers of xylose randomly branched with 4-O-methyl-D-glucuronic acid residues linked by α(1 → 2) bonds, which display bioactive properties. We have developed a simple and integrated method for the production of acidic XOS by enzymatic hydrolysis of a glucurono-xylan from beechwood. Among the enzymes screened, Depol 670L (a cellulolytic preparation from Trichoderma reesei) displayed the highest activity (70.3 U/mL, expressed in reducing xylose equivalents). High-performance anion-exchange chromatography coupled with pulsed amperometric detection (HPAEC-PAD) analysis revealed the formation of a neutral fraction (corresponding to linear XOS, mainly xylose and xylobiose) and a group of more retained products (acidic XOS), which were separated using strong anion-exchange cartridges. The acidic fraction contained a major product, characterized by matrix-assisted laser desorption/ionization-time of flight (MALDI-TOF) mass spectrometry and mono- and two-dimensional nuclear magnetic resonance spectroscopy (NMR) as 2′-O-α-(4-O-methyl-α-D-glucuronosyl)-xylobiose (X2_MeGlcA). Starting from 2 g of beechwood xylan, 1.5 g of total XOS were obtained, from which 225 mg (11% yield) corresponded to the aldouronic X2_MeGlcA. The acidic XOS exhibited higher antioxidant activity (measured by the ABTS·+ discoloration assay) than xylan, whilst neutral XOS displayed no antioxidant activity. This work demonstrates that it is possible to obtain a safe and natural antioxidant by enzymatic biotransformation of hardwood hemicellulose.

The short ionizing photon mean free path at z = 6 in Cosmic Dawn III, a new fully coupled radiation-hydrodynamical simulation of the Epoch of Reionization

ABSTRACT Recent determinations of the mean free path of ionizing photons (mfp) in the intergalactic medium (IGM) at z = 6 are lower than many theoretical predictions. In order to gain insight, we investigate the evolution of the mfp in our new massive fully coupled radiation-hydrodynamics cosmological simulation of reionization: Cosmic Dawn III (CoDa III). CoDa III’s scale ($\rm 94^3 \, cMpc^3$) and resolution ($\rm 8192^3$ grid) make it particularly suitable to study the IGM during reionization. The simulation was performed with ramses-cudaton on Summit, and used 13 1072 processors coupled to 24 576 GPUs, making it the largest reionization simulation, and largest ever ramses simulation. A superior agreement with global constraints on reionization is obtained in CoDa III over Cosmic Dawn II (CoDa II), especially for the evolution of the neutral hydrogen fraction and the cosmic photoionization rate, thanks to an improved calibration, later end of reionization (z = 5.6), and higher spatial resolution. Analysing the mfp, we find that CoDa III reproduces the most recent observations very well, from z = 6 to z = 4.6. We show that the distribution of the mfp in CoDa III is bimodal, with short (neutral) and long (ionized) mfp modes, due to the patchiness of reionization and the coexistence of neutral versus ionized regions during reionization. The neutral mode peaks at sub-kpc to kpc scales of mfp, while the ionized mode peak evolves from 0.1 Mpc h−1 at z = 7 to ∼10 Mpc h−1 at z = 5.2. Computing the mfp as the average of the ionized mode provides the best match to the recent observational determinations. The distribution reduces to a single neutral (ionized) mode at z > 13 (z < 5).

Local effects during ion scattering on adsorbate-covered surfaces

This study addresses the importance of adsorbate-induced local effects during collisions between projectiles and adsorbate-covered surfaces. Various systems are investigated: H− on Na/Ag(111); H− on Na/Cu(111); and Li+ on K/Al(100), by using wave packet propagation methods. From the projectile's perspective, the adsorbate's presence on the surface can be felt from up to a few tens of atomic units away when the projectile is close to the surface, and up to 100 a.u or more when the projectile is on top of adsorbate. This is a well-defined bell-shape region around the adsorbate. However, the scattered ion/neutral fractions are not significantly affected unless the projectile impacts the surface in the close 10–15 a.u. vicinity of the adsorbate. Scattering from adsorbate sites compared to scattering from substrate sites produces very different ion/neutral fractions, that vary not only with the surface coverage, but especially with the distance from the projectile's point of impact on the surface to the adsorbate. Our calculated Li neutral fractions obtained after scattering Li+ from K/Al(100) are in satisfactory agreement with the experimental results.

Evaluation of prediction of indigestible fiber fraction (iNDF) of whole-crop barley silage by using non-destructive spectroscopic techniques as a fast-screening method: comparison between FTIR vs. NIR

The objective of this study was to reveal the potential of using Fourier transform mid-infrared (FTIR) and near infrared (NIR) spectroscopy as tools for the determination of indigestible neutral (NDF) fraction (iNDF) of whole-crop barley silage. A total of 48 whole-crop barley silage samples collected from 48 different farms in Western Canada were analyzed for iNDF. Reference values were matched with NIR and FTIR spectra. Spectral data processing (pretreatments) included first derivative, standard normal variate, multiplicative scattering correction, second derivative, and orthogonal signal correction. Prediction equations were obtained from each model using an external validation set. The coefficient of determination for the external validation of iNDF was 0.62 for FTIR and 0.41 for NIR, while the corresponding ratio performance deviation was 1.69 and 1.38 for FTIR and NIR, respectively. Results from this research showed the high potential of applying infrared molecular spectroscopy for the examination of forage plant fiber digestibility. More studies are needed to improve the accuracy and performance of FTIR and NIR spectroscopies in predicting the iNDF of whole-crop barley silage samples.

Enhancement of Lipid and Biomass Production in Microalgae Scenedesmus abundans by Microwave Irradiation

Due to the rising depletion of fossil fuels and increased energy demands, human society is looking for clean sustainable energy. Commercially produced algal biodiesel is limited by the expense and difficulty of oil extraction and subsequent biodiesel conversion technologies. Microalgae with high oil content are only alternatives for decreasing fossil fuel supplies, but more work remains to be done to improve the lipid content of microalgae strains. In this study, strain improvement is done using microwave radiation in Scenedesmus abundans to increase the production of triacylglycerol, which is the main source of biodiesel. Microalgal cultures were exposed to varied microwave irradiation over different time periods. Under microwave irradiation, 20-25 mins reaction time seems suitable for the complete in situ transesterification reaction. Microwave heating transesterification has been shown to be more effective for adequate biodiesel yield compared to the conventional transesterification process. Maximum increase of 2.22-fold in biomass, and 2.5-fold in triacylglycerol was observed for microwave irradiation of 25 mins and 20 mins intervals respectively. The percentage of some monounsaturated fatty acids increased in gas chromatographic examination of neutral lipid fractions from total lipids of microwave irradiated samples, is considered as one of the preferable properties of biodiesel. According to our study findings, Scenedesmus abundans qualifies as the most efficient feedstock for biodiesel production, and microwave-assisted in situ transesterification reduces the requirement for a large amount of solvents, longer reaction times, and high reaction temperatures and pressures.

Ancestral Lineages in Mutation Selection Equilibria with Moving Optimum.

Many populations can somehow adapt to rapid environmental changes. To understand this fast evolution, we investigate the genealogy of individuals inside those populations. More precisely, we use a deterministic model to describe the phenotypic density of a population under selection when the fitness optimum moves at constant speed. We study the inside dynamics of this population using the neutral fractions approach. We then define a Markov process characterizing the distribution of ancestral phenotypic lineages inside the equilibrium. This construction yields qualitative as well as quantitative properties on the phenotype of typical ancestors. In particular, we show that in asexual populations typical ancestors of present individuals carried traits much closer to the fitness optimum than most individuals alive at the same time. We also investigate more deeply the asymptotic regime of small mutation effects. In this regime, we obtain an explicit formula for the typical ancestral lineage using the description of the solutions of the Hamilton Jacobi equation as a minimizer of an optimization problem. In addition, we compare our deterministic results on lineages with the lineages of stochastic models.

Production of antihypertensive and antidiabetic peptide fractions from quinoa (Chenopodium quinoa Willd.) by electrodialysis with ultrafiltration membranes

Processing bioactive peptides from natural sources using electrodialysis with ultrafiltration membranes (EDUF) have gained attention since it can fractionate in terms of their charge and molecular weight. Quinoa is a pseudo-cereal highlighted by its high protein content, amino acid profile and adapting growing conditions. The present work aimed at the production of quinoa peptides through fractionation using EDUF and to test the fractions according to antihypertensive and antidiabetic activity. Experimental data showed the production of peptides ranging between 0.4 and 1.5 kDa. Cationic (CQPF) (3.01 %), anionic (AQPF) (1.18 %) and the electrically neutral fraction quinoa protein hydrolysate (QPH)-EDUF (∼95 %) were obtained. In-vitro studies showed the highest glucose uptake modulation in L6 cell skeletal myoblasts in presence of QPH-EDUF and AQPF (17 % and 11 %) indicating potential antidiabetic activity. The antihypertensive effect studied in-vivo in spontaneously hypertensive rats (SHR), showed a decrease in systolic blood pressure in presence of the fractionated peptides, being 100 mg/kg a dose comparable to Captopril (positive control). These results contribute to the current knowledge of bioactive peptides from quinoa by reporting the relevance of EDUF as tool to produce selected peptide fractions. Nevertheless, further characterization is needed towards peptide sequencing, their respective role in the metabolism and scaling-up production using EDUF.

Evaluation of maturation promoting factor in polychaete ( Marphysa sp.) on Indian White Prawn , Penaeus indicus female broodstock

Polychaete is considered the best maturation diet for penaeids; however, fluctuating supply and quality warrant detailed studies to understand the specific maturation-promoting factors present in polychaete. Indian white prawn, Penaeus indicus, was fed diets supplemented with different fractions of Marphysa sp. extracts. Fractions, such as the total soluble fraction (TSF), neutral lipid fraction (NLF), and polar lipid fraction (PLF), were incorporated in the maturation diet at 0.25, 0.50, and 1.00% following a 3 × 3 factorial design. One group was fed with basal diet (BD), and another was fed with fresh squid, mussel, and polychaete, serving as the control. After a 30-day feeding trial, results showed that the inclusion of polychaete extracts in the diet significantly improved P. indicus maturation compared to groups fed BD and control with 40% maturation rates (MR) (p = 3.4 × 10−4). MR was optimum in groups receiving diets supplemented with ≥0.5% TSF (70.00% ± 0.00) and NLF (60.00% ± 5.77). Similar improved MR was achieved in treatments receiving ≥0.25% PLF supplementation (60% ± 0.00). Accordingly, relative expression of ovarian vitellogenin mRNA of broodstock fed under 0.25 and 0.50% PLF group was 4.44 and 3.96 folds higher than BD, respectively (p = 0.003). No significant differences were detected in the broodstock survival, latency period, hepatosomatic, and gonadosomatic indices. Biochemical content analyses showed no significant differences among the nine treatments except for broodstock's higher ovary protein content in the TSF group (p = 0.037). This study highlights PLF as the most potent component of the polychaete extract in promoting gonad maturation in P. indicus maturation supplemented at a 0.25% optimum inclusion level.

Geochemical features of altered carbonaceous mudstones from Troyanovo-3 mine borehole (Maritsa Iztok lignite field, Bulgaria)

We sampled and studied a borehole located in the southern part of Maritsa Iztok lignite field (Bulgaria) which comprises Late Miocene-Pliocene sediments of Maritsa Formation. The current report of Troyanovo-3 Mine sequence is the first to our knowledge. It represents a lignite-mudstone succession with variations in organic matter (OM) maturity. Thirty eight coal and mudstone core samples showed predictable ash and sulfur content. The XRD study showed illite/muscovite, illite/smectite, kaolinite, chlorite and quartz as main constituents that argue for a detrital origin. Additionally, we identified pyrite and gypsum and some peaks of marcasite and elemental sulfur. A set of eight mudstone samples rich in OM was selected for further geochemical analyses. The OM was classified as type III and II/III kerogen based on Rock-Eval pyrolysis data. The low amounts of extractable organic matter (0.01–2.25%) we found are consistent with the samples' low maturity and kerogen type. The yields of two samples were too low for further fractionation. Asphaltene amount (26.1–79.7%) predominates in the extracts. Diterpenoids (neutral fraction) and their polar analogues (slightly polar fraction) are highly abundant. In slightly polar fractions we registered ketotriterpenoids (mainly lupenones) in addition to the linear n-alkan-2-ones.OM elevated maturity of the deepest sample (59.60 m depth) was evidenced mainly by hopane distributions, i.e. Ts/(Tm + Ts), homohopane H31αβ index, hopane ratios (H29αβ/H30αβ) and H27β/H27α. The organic geochemistry results do not fit the ordinary regional maturity trend. OM maturity variation, superimposed over natural low coalification degree, could be ascribed to an interaction with ascending hot reductive fluids. The sulfide mineralization found in the fractures also gives indications about the fluid circulation. Another thermal alteration affecting the middle part samples (24.0–28.3 m) was suggested due to elevated Tmax values and HI and OI relation for a charcoal piece and carbonaceous mudstone. Smoldering processes affecting these samples were presumed.Low-temperature alteration processes were identified by n-alkanes, n-alkan-2-ones, and n-alcohols expulsion and downwards migration (from 18.0 m to 30.0 m) accompanied by a clear terpenoids depletion. The 17,21-seco-hopane-17,21-dione found for the first time for Maritsa Iztok Basin (MIB) samples further suggested processes of water seepage and wash-out. Microbial degradation activities usually accompanying water-washing possibly led to a specific n-alkan-2-one distribution. All the features we report point to either an even-numbered n-alkanoic acid decarboxylation or to a selective microbial degradation of odd-numbered n-alkanes to n-alkan-2-ones. In all, the history of the coal-mudstone sequence is complex, overprinted by variable alteration processes, first ever reported for MIB samples.

Intravital Subcellular Microscopy of the Mammary Gland.

The mammary gland constitutes a model par excellence for investigating epithelial functions, including tissue remodeling, cell polarity, and secretory mechanisms. During pregnancy, the gland expands from a primitive ductal tree embedded in a fat pad to a highly branched alveolar network primed for the formation and secretion of colostrum and milk. Post-partum, the gland supplies all the nutrients required for neonatal survival, including membrane-coated lipid droplets (LDs), proteins, carbohydrates, ions, and water. Various milk components, including lactose, casein micelles, and skim-milk proteins, are synthesized within the alveolar cells and secreted from vesicles by exocytosis at the apical surface. LDs are transported from sites of synthesis in the rough endoplasmic reticulum to the cell apex, coated with cellular membranes, and secreted by a unique apocrine mechanism. Other preformed constituents, including antibodies and hormones, are transported from the serosal side of the epithelium into milk by transcytosis. These processes are amenable to intravital microscopy because the mammary gland is a skin gland and, therefore, directly accessible to experimental manipulation. In this paper, a facile procedure is described to investigate the kinetics of LD secretion in situ, in real-time, in live anesthetized mice. Boron-dipyrromethene (BODIPY)665/676or monodansylpentane are used to label the neutral lipid fraction of transgenic mice, which either express soluble EGFP (enhanced green fluorescent protein) in the cytoplasm, or a membrane-targeted peptide fused to either EGFP or tdTomato. The membrane-tagged fusion proteins serve as markers of cell surfaces, and the lipid dyes resolve LDs ≥ 0.7 µm. Time-lapse images can be recorded by standard laser scanning confocal microscopy down to a depth of 15-25 µm or by multiphoton microscopy for imaging deeper in the tissue. The mammary gland may be bathed with pharmacological agents or fluorescent dyes throughout the surgery, providing a platform for acute experimental manipulations as required.

Chemical abundances in Seyfert galaxies – IX. Helium abundance estimates

ABSTRACT For the first time, the helium abundance relative to hydrogen (He/H), which relied on direct measurements of the electron temperature, has been derived in the narrow line regions (NLRs) from a local sample of Seyfert 2 nuclei. In view of this, optical emission line intensities [3000 < λ(Å) < 7000] of 65 local Seyfert 2 nuclei (z < 0.2), taken from Sloan Digital Sky Survey Data Release 15 and additional compilation from the literature, were considered. We used photoionization model grid to derive an Ionization Correction Factor (ICF) for the neutral helium. The application of this ICF indicates that the NLRs of Seyfert 2 present a neutral helium fraction of ∼50 per cent in relation to the total helium abundance. We find that Seyfert 2 nuclei present helium abundance ranging from 0.60 to 2.50 times the solar value, while ∼85 per cent of the sample present oversolar abundance values. The derived (He/H)–(O/H) abundance relation from the Seyfert 2 is stepper than that of star-forming regions (SFs) and this difference could be due to excess of helium injected into the interstellar medium by the winds of Wolf–Rayet stars. From a regression to zero metallicity, by using Seyfert 2 estimates combined with SFs estimates, we obtained a primordial helium mass fraction Yp = 0.2441 ± 0.0037, a value in good agreement with the one inferred from the temperature fluctuations of the cosmic microwave background by the Planck Collaboration, i.e. $Y_{\rm p}^{\rm Planck}=0.2471\pm 0.0003$.

Hydrogen reionization ends by z = 5.3: Lyman-α optical depth measured by the XQR-30 sample

ABSTRACT The presence of excess scatter in the Ly-α forest at z ∼ 5.5, together with the existence of sporadic extended opaque Gunn-Peterson troughs, has started to provide robust evidence for a late end of hydrogen reionization. However, low data quality and systematic uncertainties complicate the use of Ly-α transmission as a precision probe of reionization’s end stages. In this paper, we assemble a sample of 67 quasar sightlines at z > 5.5 with high signal-to-noise ratios of >10 per ≤15 km s−1 spectral pixel, relying largely on the new XQR-30 quasar sample. XQR-30 is a large program on VLT/X-Shooter which obtained deep (SNR > 20 per pixel) spectra of 30 quasars at z > 5.7. We carefully account for systematics in continuum reconstruction, instrumentation, and contamination by damped Ly-α systems. We present improved measurements of the mean Ly-α transmission over 4.9 < z < 6.1. Using all known systematics in a forward modelling analysis, we find excellent agreement between the observed Ly-α transmission distributions and the homogeneous-UVB simulations Sherwood and Nyx up to z ≤ 5.2 (<1σ), and mild tension (∼2.5σ) at z = 5.3. Homogeneous UVB models are ruled out by excess Ly-α transmission scatter at z ≥ 5.4 with high confidence (>3.5σ). Our results indicate that reionization-related fluctuations, whether in the UVB, residual neutral hydrogen fraction, and/or IGM temperature, persist in the intergalactic medium until at least z = 5.3 (t = 1.1 Gyr after the big bang). This is further evidence for a late end to reionization.

Evaluation of heavy metal availability in soils near former zinc smelters by chemical extractions and geochemical modelling

Multi-surface modelling (MSM) is an important tool to predict heavy metal partitioning and speciation in soils. However, calcareous clay soils contaminated by smelting activities and mine waste have so far received little attention in MSM studies. In this work, 6 paired soil samples taken nearby former Zn smelters and at further distance were used for quantifying the essential input parameters for MSM including the size of the geochemically reactive pool of heavy metals and the reactivity of soil organic matter (SOM) for metal binding. The reactive heavy metal pool (Cd, Cu, Ni, Pb, and Zn) in these samples was determined by extracting soil with 0.43 M HNO3 and 0.005 M DTPA. For both extraction methods, the contribution of all heavy metals to their total contents was larger in most of the soil samples taken nearby former Zn smelters than in the paired samples from further distance. Furthermore, the amounts of heavy metals extracted with 0.43 M HNO3 were consistently larger than those extracted with 0.005 M DTPA. The sum of the humic acid (HA), fulvic acid (FA) + hydrophobic organic neutral (HON) fraction varied between 6.2 and 43% of total SOM with an average of 24%, which is at the lower end of what is commonly reported in literature. The lower SOM reactivity might be attributed to a lower humification rate of fresh soil organic matter due to heavy metal contamination. The accuracy of the MSM-predicted predictions of solubility of the heavy metals, especially for Ni and Zn, was higher when the results of the DTPA extraction method were used as model input, than when using the results of the HNO3 extraction method, especially when the soil carbonate content was > 4%. Hence, the measurement of the geochemical reactivity of heavy metals by the 0.005 M DTPA extraction method and the reactivity of SOM enable adequate MSM predictions of the solubility of heavy metals in smelter slag-contaminated calcareous clay soils.