Ablating Adult Neurogenesis in the Rat Has No Effect on Spatial Processing: Evidence from a Novel Pharmacogenetic Model

The function of adult neurogenesis in the rodent brain remains unclear. Ablation of adult born neurons has yielded conflicting results about emotional and cognitive impairments. One hypothesis is that adult neurogenesis in the hippocampus enables spatial pattern separation, allowing animals to distinguish between similar stimuli. We investigated whether spatial pattern separation and other putative hippocampal functions of adult neurogenesis were altered in a novel genetic model of neurogenesis ablation in the rat. In rats engineered to express thymidine kinase (TK) from a promoter of the rat glial fibrillary acidic protein (GFAP), ganciclovir treatment reduced new neurons by 98%. GFAP-TK rats showed no significant difference from controls in spatial pattern separation on the radial maze, spatial learning in the water maze, contextual or cued fear conditioning. Meta-analysis of all published studies found no significant effects for ablation of adult neurogenesis on spatial memory, cue conditioning or ethological measures of anxiety. An effect on contextual freezing was significant at a threshold of 5% (P = 0.04), but not at a threshold corrected for multiple testing. The meta-analysis revealed remarkably high levels of heterogeneity among studies of hippocampal function. The source of this heterogeneity remains unclear and poses a challenge for studies of the function of adult neurogenesis.     

Biofouling leads to reduced shell growth and flesh weight in the cultured mussel Mytilus galloprovincialis

Competitive interactions between cultured mussels and fouling organisms may result in growth and weight reductions in mussels, and compromised aquaculture productivity. Mussel ropes were inoculated with Ciona intestinalis, Ectopleura crocea or Styela clava, and growth parameters of fouled and unfouled Mytilus galloprovincialis were compared after two?months. Small mussels (≈50?mm) fouled by C. intestinalis and E. crocea were 4.0 and 3.2% shorter in shell length and had 21 and 13% reduced flesh weight, respectively, compared to the controls. Large mussels (≈68?mm) fouled by S. clava, C. intestinalis and E. crocea were 4.4, 3.9 and 2.1% shorter than control mussels, respectively, but flesh weights were not significantly reduced. A series of competitive feeding experiments indicated that S. clava and C. intestinalis did not reduce mussels’ food consumption, but that E. crocea, through interference competition, did. Fouling by these species at the densities used here reduced mussel growth and flesh weight, likely resulting in economic losses for the industry, and requires consideration when developing biofouling mitigation strategies.     

Field screening of barley cultivars to soil salinity using a sprinkler and a drip irrigation system

The establishment of proper agronomical practices and plant breeding programs for saline environments is limited by the lack of adequate field screening methods. We assessed the relationships between leaf ion concentration and grain yield in a set of barley cultivars and compared their ranking for salinity tolerance established with a triple-line-source (TLS) sprinkler system, where the absorption of salts is through the leaves and the roots, with that obtained with a drip-irrigation (DI) system, where the absorption of salts is only through the roots. The saline solution in both systems was made up of sodium and hydrated calcium chloride (1:1 w/w). Except for the highest saline treatments, direct leaf absorption of toxic Na⁺ and Cl^- was minor or negligible, but it was substantial for Ca²+. Irrespective of barley cultivar and leaf age, the accumulation of Cl^- in the TLS was 1.5–2.5 times greater than Na⁺. There was no significant correlation between grain yield and leaf sap ion concentration among eighteen barley cultivars. Thus, leaf ion concentrations should not be used as screening tools in breeding programs for increasing salinity tolerance in barley. The highest-yielding cultivars under non-saline conditions were also most productive under moderately saline conditions, though not under high-saline conditions. Although grain yields of the eighteen barley cultivars in the TLS were substantially lower than in the DI, the salinity tolerances estimated in both systems were significantly correlated (P < 0.05), indicating that the simple and inexpensive TLS irrigation system could be successfully used in screening for salinity tolerance in barley.     

Size-fractionated mesozooplankton biomass, metabolism and grazing along a 50{degrees}N-30{degrees}S transect of the Atlantic Ocean

Size-fractionated mesozooplankton grazing and metabolism wereinvestigated along the wide latitudinal range (50°N–30°S)covered during the Atlantic Meridional Transect (AMT) 11 cruise.Five different oceanic provinces were traversed in this cruise:North Atlantic Drift (NADR), North Atlantic Subtropical Gyral(NAST), Canary Coastal (CNRY), Eastern Tropical Atlantic (ETRA),and South Atlantic Gyral (SATL). CNRY and ETRA were affectedby the upwelling Mauritanian and equatorial respectively andprimary production in these provinces was higher than in theoligotrophic subtropical gyres (NAST and SATL). Both mesozooplanktonand phytoplankton biomass were highest around the equator. Theamount of chlorophyll a ingested daily by copepods was noticeablyhigher in mesotrophic than in oligotrophic provinces as shownby the spatial distribution of gut content values and the highabundances of copepods recorded at the equator. Grazing impactalong the transect ranged from 0.2 to 5.6% of the phytoplanktonstanding stock and from 1.6 to 14.5% of primary production.If only phytoplankton >2 µm are considered, the rangesare 1.0–19.4% (stock) and 3.4–44.7% (primary production).Grazing impact upon both phytoplankton biomass and primary productionfollowed a spatial distribution similar to that of chlorophylla ingestion, with higher values in upwelling zones than in thegyres. Weight-specific rates of respiration and NH₄⁺ and PO₄^3–excretion showed large variability both along the transect andwithin provinces, but did not differ between provinces. Therefore,zooplankton assemblages inhabiting the different provinces visitedin the AMT 11 seem to be adapted to the prevailing thermal conditions.Given the substantial proportion of nitrogen and phosphorusthat are supplied to primary producers through the excretoryactivity of mesozooplankton (the percentage of nitrogen andphosphorus requirements of phytoplankton accounted for by mesozooplanktonexcretion was >30% in all the provinces) it follows thatthey may play a crucial role as nutrient regenerators, especiallyin the oligotrophic gyres where regenerated production dominates.     

Genetic control of single lumen formation in the zebrafish gut

Most organs consist of networks of interconnected tubes that serve as conduits to transport fluid and cells and act as physiological barriers between compartments. Biological tubes are assembled through very diverse developmental processes that generate structures of different shapes and sizes. Nevertheless, all biological tubes invariably possess one single lumen. The mechanisms responsible for single lumen specification are not known. Here we show that zebrafish mutants for the MODY5 and familial GCKD gene tcf2 (also known as vhnf1) fail to specify a single lumen in their gut tube and instead develop multiple lumens. We show that Tcf2 controls single lumen formation by regulating claudin15 and Na+/K+-ATPase expression. Our in vivo and in vitro results indicate that Claudin15 functions in paracellular ion transport to specify single lumen formation. This work shows that single lumen formation is genetically controlled and appears to be driven by the accumulation of fluid.     

Fine‐scale coexistence between Mediterranean mesocarnivores is mediated by spatial,temporal, and trophic resource partitioning

1. The partition of the ecological niche can enhance the coexistence of predators due to differences in how they exploit three main resources: food, space, and time, the latter being an axis that often remains unexplored.
2. We studied niche segregation in a Mediterranean mesocarnivore community composed by Vulpes vulpes, Genetta genetta, Meles meles, and Herpestes ichneumon, addressing simultaneously different niche axes: the temporal, trophic, and spatial axes.
3. We assessed temporal segregation between mesopredators and prey and between potential competitors, using camera trap data between 2018 and 2020 in a Mediterranean landscape in Southern Spain. We deployed camera traps in 35 stations in three sites with varying vegetation cover within Doñana National Park. We further examined the spatial overlap in activity centers and trophic preferences between potential competitors using diet information from studies performed in the study area.
4. We found an overall temporal segregation between trophic generalist species, with species showing higher temporal overlap differing in their trophic preferences and/or showing limited spatial overlap. Furthermore, we observed an overall high overlap between the activity patterns of predators and their major prey in the area (the common genet vs. small mammals and the red fox vs. European rabbit).
5. Our study suggests that coexistence of the different species that compose the mesocarnivore assemblage in Mediterranean landscapes can be facilitated by subtle differences along the three main niche axes, with temporal segregation being a most pronounced mechanism. Our findings reinforce the idea that the coexistence mechanisms underlying community structure are multidimensional.

     

<Emphasis Type="Italic">Candida haemulonii</Emphasis> sensu lato: Update of the Determination of Susceptibility Profile in Argentina and Literature Review

Purpose of review

This review summarizes the information available of Candida haemulonii sensu lato, and updates the in vitro susceptibility profile of the isolates of these species from Argentina. C. haemulonii sensu lato causes fungemia in low frequency in adults and children; however, the knowledge about this emerging yeast is relevant since it is considered as a multi-resistant pathogen.

Recent findings

The discovery of new antifungal molecules, the determination of epidemiological cutoff value and clinical breakpoints for some yeasts of clinical impact, and the update of techniques to determine the in vitro susceptibility profile to yeast have generated some available information, although, for C. haemulonii sensu lato, this information is not always useful for clinical application.

Summary

We determined the susceptibility profile of C. haemulonii sensu lato strains isolated in Argentina, as a first step to establish the epidemiological cutoff values in our region. We also review the current situation in other countries.

     

Spectral and lifetime fluorescence imaging microscopies: new modalities of multiphoton microscopy applied to tissue or cell engineering

Spectral and multiphoton imaging is the preferred approach for non-invasive study allowing deeper penetration to image molecular processes in living cells. But currently available fluorescence microscopic techniques based on fluorescence intensity, such as confocal or multiphoton excitation, cannot provide detailed quantitative information about the dynamic of complex cellular structure (molecular interaction). Due to the variation of the probe concentration, photostability, cross-talking, its effects cannot be distinguished in simple intensity images. Therefore, Time Resolved fluorescence image is required to investigate molecular interactions in biological systems. Fluorescence lifetimes are generally absolute, sensitive to environment, independent of the concentration of the probe and allow the use of probes with overlapping spectra but that not have the same fluorescence lifetime. In this work, we present the possibilities that are opened up by Fluorescence Lifetime Imaging Microscopy, firstly to collect images based on fluorescence lifetime contrast of GFP variants used as a reporter of gene expression in chondrocytes and secondly, to measure molecular proximity in erythrocyte (glycophorin/membrane) by Fluorescence Resonance Energy Transfer (FLIM-FRET).