Les enfants nés prématurés présentent souvent un retard de croissance extra-utérin (RCEU) qui affecte les capacités cognitives de l’enfant et augmente le risque de maladies métaboliques à terme. La ...mise en place d’une nutrition optimale pour éviter un RCEU chez le prématuré est donc une priorité des néonatologistes. Par ailleurs, l’apport du lait maternel a été montré comme bénéfique chez les prématurés mais résulte souvent en un gain de poids sous-optimal qui peut s’expliquer par de grandes variations nutritionnelles dans la composition du lait maternel en particulier des fractions protéique et lipidique durant la période de lactation. Ainsi, des informations précises sur les contenus énergétiques des laits maternels sont essentielles pour nourrir de façon adéquate les enfants prématurés. Dans ce contexte, nous avons analysé la composante lipidomique du lait maternel et l’avons comparé à la croissance des enfants prématurés durant leurs premières semaines de vie.
Dans le cadre de l’étude LACTACOL (Clinical Trial-NCT01493063), nous avons inclus une sous-cohorte de 18 nouveau-nés ayant un âge gestationnel inférieur à 34 semaines d’aménorrhée et présentant une croissance considérée comme optimale (n=9) ou sous-optimale (n=9) sur la base de la différence de Z-score de poids entre la sortie d’hospitalisation et la naissance selon les courbes d’Olsen. Un prélèvement représentatif de 24heures de lait maternel a été réalisé de façon hebdomadaire chez les mères durant toute la durée d’hospitalisation des enfants. La fraction lipidomique du lait maternel a été analysée par une approche métabolomique par chromatographie liquide haute résolution couplée à la spectrométrie de masse. Les profils lipidomiques des laits maternels ont été mis en relation avec la trajectoire pondérale des enfants nés prématurés à l’aide d’outils statistiques multivariés.
Un modèle d’analyse non supervisée en composante principale construit à partir des 3280 variables des profils lipidomiques des laits maternels montre deux phénotypes de lait associés chacun à un des groupes de croissance optimale ou sous-optimale des nouveau-nés prématurés. L’analyse supervisée de ces profils lipidomiques nous a permis de mettre en évidence 141 métabolites qui discriminent très nettement les deux phénotypes de laits maternels sur les deux premières composantes (62 % de la variabilité Y-croissance des enfants) avec un taux d’erreur de classement de seulement 7 %. Une régression PLS construite à partir de ces 141 biomarqueurs montre, après validation croisée, une prédiction très satisfaisante du Z-score pondéral hebdomadaire des 18 nouveau-nés prématurés entre leur deuxième et sixième semaine d’âge postnatal. Actuellement, 26 de ces biomarqueurs ont pu être annotés et correspondent majoritairement à des phosphatidylcholines ou des triglycérides.
Cette étude montre l’intérêt de la métabolomique en tant qu’outil pour améliorer les connaissances sur la composition du lait maternel et à plus long terme, d’orienter les pratiques nutritionnelles des enfants nés prématurés.
Resistance to organophosphorus insecticides (OP) in Culex pipiens mosquitoes represents a convenient model for investigating the fitness cost of resistance genes and its origin, since both the ...environmental changes in nature and the adaptive genes are clearly identified. Two loci are involved in this resistance – the super-locus Ester and the locus Ace.1 – each displaying several resistance alleles. Population surveys have shown differences in fitness cost between these resistance genes and even between resistance alleles of the same locus. In order to better understand this fitness cost and its variability, the effects of these resistance genes on several fitness-related traits are being studied. Here, through competition experiments between two males for the access to one female, we analysed the effect on paternity success associated with three resistance alleles – Ester4, Ester1 and Ace.1R – relative to susceptible males and relative to one another. The eventual effect of female genotype on male mating success was also studied by using susceptible and resistant females. The strains used in this experiment had the same genetic background. Susceptible males had a mating advantage when competing with any of the resistant males, suggesting a substantial cost of resistance genes to this trait. When competing against susceptible males, the paternity success did not vary among resistant males, whatever the genotype of the female. When competing against other resistant males, no difference in paternity success was apparent, except when the female was Ester1.
The independent effects of herbivores and neighbors on plants are generally negative, and therefore the combined effects of these interactions are generally assumed to have additive or multiplicative ...negative effects on plant growth. However, because herbivores can stimulate the growth of plants (compensation) and neighbors can facilitate each other, the combined effects of herbivory and plant-plant interactions can be highly variable and poorly predicted by current competition and plant-herbivore theory. In some cases in North America, Festuca species appear to facilitate invasive Centaurea species and enhance their compensatory responses in controlled greenhouse conditions. We explored the interactions between herbivory and neighbor effects in the French Alps by testing the effect of the neighbor, Festuca paniculata L., on the compensatory growth response of defoliated Centaurea uniflora L. over two growing seasons. Seventy percent of aboveground C. uniflora biomass was clipped at each of seven times throughout two growing seasons in the presence or absence of F. paniculata. Centaurea uniflora compensated for severe damage in the first year, but was negatively affected by defoliation in the second year. Defoliating C. uniflora reduced final aboveground biomass by 44% and flower number by 64%, but did not affect survival. Unlike observations for other Centaurea and Festuca species, F. paniculata had significant competitive effects on C. uniflora. Festuca paniculata neither enhanced compensatory responses of C. uniflora nor increased the negative effects of defoliation. Our results show that compensatory responses can weaken over time, but that neighboring plants do not necessarily increase the negative effects of defoliation.
Two strains of mesophilic lactic acid bacteria, Streptococcus cremoris AM2 and Leuconostoc lactis CNRZ 1091, were grown in pure and mixed cultures in the presence or absence of citrate (15 mM) and at ...controlled (pH 6.5) or uncontrolled pH. Microbial cell densities at the end of growth, maximum growth rates, the pH decrease of the medium resulting from growth, and the corresponding acidification rates were determined to establish comparisons. The control of pH in pure cultures had no effect on L. lactis CNRZ 1091 populations. The final populations of S. cremoris AM2, however, were at least five times higher than when the pH was not controlled (4 X 10(8) vs. 2 X 10(9) CFU . ml-1). The pH had no effect on the growth rate of either strain. That of S. cremoris AM2 (0.8 h-1) was about twice that of L. lactis CNRZ 1091. When the pH fell below 5,the growth of both strains decreased or stopped altogether. Citrate had no effect on S. cremoris AM2, while final populations of L. lactis CNRZ 1091 were two to three times higher (3 X 10(8) CFU . ml-1); it had no effect on the maximum growth rates of the two strains. Citrate attenuated the pH decrease of the medium and reduced the maximum acidification rate of the culture by 50%, due to the growth of S. cremoris AM2. Acidification due to L. lactis CNRZ 1091, however, was very slight. Regardless of the conditions of pH and citrate, the total bacterial population in mixed culture was lower (by 39%) than that of the sum of each pure culture. Mixed culture improved the maximum growth rate of L. lactis CNRZ 1091 (0.6 h-1) by 50%, while that of S. cremoris AM2 was unaffected. The acidification rate of the growth medium in mixed culture, affected by the presence of citrate, resulted from the development and activity of S. cremoris AM2
A&A 654, A128 (2021) We characterize the ionized gas outflows in 15 low-redshift star-forming
galaxies, a Valpara\'iso ALMA Line Emission Survey (VALES) subsample, using
MUSE integral field ...spectroscopy and GAMA photometric broadband data. We
measure the emission-line spectra by fitting a double-component profile, with
the second and broader component being related to the outflowing gas. This
interpretation is in agreement with the correlation between the observed
star-formation rate surface density ($\Sigma_{\mathrm{SFR}}$) and the
second-component velocity dispersion ($\sigma_{\mathrm{2nd}}$), expected when
tracing the feedback component. By modelling the broadband spectra with spectra
energy distribution (SED) fitting and obtaining the star-formation histories of
the sample, we observe a small decrease in SFR between 100 and 10 Myr in
galaxies when the outflow H$\alpha$ luminosity contribution is increased,
indicating that the feedback somewhat inhibits the star formation within these
timescales. The observed emission-line ratios are best reproduced by
photoionization models when compared to shock-ionization, indicating that
radiation from young stellar population is dominant, and seems to be a
consequence of a continuous star-formation activity instead of a bursty event.
The outflow properties such as mass outflow rate ($\sim 0.1\,$M$_\odot$
yr$^{-1}$), outflow kinetic power ($\sim 5.2 \times 10^{-4}\%
L_{\mathrm{bol}}$) and mass loading factor ($\sim 0.12$) point towards a
scenario where the measured feedback is not strong and has a low impact on the
evolution of galaxies in general.
Over the past few years ALMA has detected dust-rich galaxies whose cold dust emission is spatially disconnected from the UV rest-frame emission. This represents a challenge for modeling their ...spectral energy distributions with codes based on an energy budget between the stellar and dust components. We want to verify the validity of energy balance modeling on a sample of galaxies observed from the UV to the sub-millimeter rest frame with ALMA and decipher what information can be reliably retrieved from the analysis of the full SED and from subsets of wavelengths. We select 17 sources at z~2 in the Hubble Ultra-Deep Field and in the GOODS- South field detected with ALMA and Herschel and for which UV to NIR. rest-frame ancillary data are available. We fit the data with CIGALE exploring different configurations for dust attenuation and star formation histories, considering either the full dataset or one that is reduced to the stellar and dust emission. We compare estimates of the dust luminosities, star formation rates, and stellar masses. The fit of the stellar continuum alone with the starburst attenuation law can only reproduce up to 50% of the total dust luminosity observed by Herschel and ALMA. This deficit is found to be consistent with similar quantities estimated in the COSMOS field and is found to increase with the specific star formation rate. The combined stellar and dust SEDs are well fitted when different attenuation laws are introduced. Shallow attenuation curves are needed for the galaxies whose cold dust distribution is very compact compared to starlight. The stellar mass estimates are affected by the choice of the attenuation law. The star formation rates are robustly estimated as long as dust luminosities are available. The large majority of the galaxies are above the average main sequence of star forming galaxies and one source is a strong starburst.
Recent studies have revealed a strong relation between sample-averaged black-hole (BH) accretion rate (BHAR) and star formation rate (SFR) among bulge-dominated galaxies, i.e., "lockstep" BH-bulge ...growth, in the distant universe. This relation might be closely related to the BH-bulge mass correlation observed in the local universe. To understand further BH-bulge coevolution, we present ALMA CO(2-1) or CO(3-2) observations of 7 star-forming bulge-dominated galaxies at z=0.5-2.5. Using the ALMA data, we detect significant (\(>3\sigma\)) CO emission from 4 objects. For our sample of 7 galaxies, we measure (or constrain with upper limits) their CO line fluxes and estimate molecular gas masses (\(M_{gas}\)). We also estimate their stellar masses (\(M_{star}\)) and SFRs by modelling their spectral energy distributions (SEDs). Using these physical properties, we derive the gas-depletion timescales (\(t_{dep} = M_{gas}/SFR\)) and compare them with the bulge/BH growth timescales (\(t_{grow} = M_{star}/SFR \sim M_{BH}/BHAR\)). Our sample generally has \(t_{dep}\) shorter than \(t_{grow}\) by a median factor of \(\gtrsim 4\), indicating that the cold gas will be depleted before significant bulge/BH growth takes place. This result suggests that the BH-bulge lockstep growth is mainly responsible for maintaining their mass relation, not creating it. We note that our sample is small and limited to \(z<2.5\); JWST and ALMA will be able to probe to higher redshifts in the near future.
Dust attenuation shapes the spectral energy distributions of galaxies and any modelling and fitting procedure of their spectral energy distributions must account for this process. We present results ...of two recent works dedicated at measuring the dust attenuation curves in star forming galaxies at redshift from 0.5 to 3, by fitting continuum (photometric) and line (spectroscopic) measurements simultaneously with CIGALE using variable attenuation laws based on flexible recipes. Both studies conclude to a large variety of effective attenuation laws with an attenuation law flattening when the obscuration increases. An extra attenuation is found for nebular lines. The comparison with radiative transfer models implies a flattening of the attenuation law up to near infrared wavelengths, which is well reproduced with a power-laws recipe inspired by the Charlot and Fall recipe. Here we propose a global modification of the Calzetti attenuation law to better reproduce the results of radiative transfer models.
Galaxy morphology is shaped by stellar activity, feedback, gas and dust
properties, and interactions with surroundings, and can therefore provide
insight into these processes. In this paper, we study ...the spatial offsets
between stellar and interstellar medium emission in a sample of 54
main-sequence star-forming galaxies at $z\sim4-6$ observed with the Atacama
Large Millimeter/submillimeter Array (ALMA) and drawn from the ALMA Large
Program to INvestigate C$^+$ at Early times (ALPINE). We find no significant
spatial offset for the majority ($\sim$ 70 percent) of galaxies in the sample
among any combination of C II, far-infrared continuum, optical, and
ultraviolet emission. However, a fraction of the sample ($\sim$ 30 percent)
shows offsets larger than the median by more than 3$\sigma$ significance
(compared to the uncertainty on the offsets), especially between C II and
ultraviolet emission. We find that these significant offsets are of the order
of $\sim$0.5-0.7 arcsec, corresponding to $\sim$3.5-4.5 kiloparsecs. The
offsets could be caused by a complex dust geometry, strong feedback from stars
and active galactic nuclei, large-scale gas inflow and outflow, or a
combination of these phenomena. However, our current analysis does not
definitively constrain the origin. Future, higher resolution ALMA and JWST
observations may help resolve the ambiguity. Regardless, since there exist at
least some galaxies that display such large offsets, galaxy models and spectral
energy distribution fitting codes cannot assume co-spatial emission in all
main-sequence galaxies, and must take into account that the observed emission
across wavelengths may be spatially segregated.
Tidal dwarf galaxies (TDGs) are low-mass objects that form within tidal and/or collisional debris ejected from more massive interacting galaxies. We use CO(\(1-0\)) observations from ALMA and ...integral-field spectroscopy from MUSE to study molecular and ionized gas in three TDGs: two around the collisional galaxy NGC 5291 and one in the late-stage merger NGC 7252. The CO and H\(\alpha\) emission is more compact than the HI emission and displaced from the HI dynamical center, so these gas phases cannot be used to study the internal dynamics of TDGs. We use CO, HI, and H\(\alpha\) data to measure the surface densities of molecular gas (\(\Sigma_{\rm mol}\)), atomic gas (\(\Sigma_{\rm atom}\)) and star-formation rate (\(\Sigma_{\rm SFR}\)), respectively. We confirm that TDGs follow the same spatially integrated \(\Sigma_{\rm SFR}-\Sigma_{\rm gas}\) relation of regular galaxies, where \(\Sigma_{\rm gas} = \Sigma_{\rm mol} + \Sigma_{\rm atom}\), even though they are HI dominated. We find a more complex behaviour in terms of the spatially resolved \(\Sigma_{\rm SFR}-\Sigma_{\rm mol}\) relation on sub-kpc scales. The majority (\(\sim\)60\(\%\)) of SF regions in TDGs lie on the same \(\Sigma_{\rm SFR}-\Sigma_{\rm mol}\) relation of normal spiral galaxies but show a higher dispersion around the mean. The remaining fraction of SF regions (\(\sim\)40\(\%\)) lie in the starburst region and are associated with the formation of massive super star clusters, as shown by Hubble Space Telescope images. We conclude that the local SF activity in TDGs proceeds in a hybrid fashion, with some regions comparable to normal spiral galaxies and others to extreme starbursts.
PDF
