Long-range neuronal circuits underlying the interaction between sensory and motor cortex

In the rodent vibrissal system, active sensation and sensorimotor integration are mediated in part by connections between barrel cortex and vibrissal motor cortex. Little is known about how these structures interact at the level of neurons. We used Channelrhodopsin-2 (ChR2) expression, combined with anterograde and retrograde labeling, to map connections between barrel cortex and pyramidal neurons in mouse motor cortex. Barrel cortex axons preferentially targeted upper layer (L2/3, L5A) neurons in motor cortex; input to neurons projecting back to barrel cortex was particularly strong. Barrel cortex input to deeper layers (L5B, L6) of motor cortex, including neurons projecting to the brainstem, was weak, despite pronounced geometric overlap of dendrites with axons from barrel cortex. Neurons in different layers received barrel cortex input within stereotyped dendritic domains. The cortico-cortical neurons in superficial layers of motor cortex thus couple motor and sensory signals and might mediate sensorimotor integration and motor learning.     

Summer variability, winter dormancy: lichen activity over 3?years at Botany Bay, 77��S latitude, continental Antarctica

Lichens make up a major component of Antarctic vegetation; they are also poikilohydric and are metabolically active only when hydrated. Logistic constraints have meant that we have little idea of the length, timing or environmental conditions of activity periods of lichens. We present the results of a three-year monitoring of the activity of the lichen Umbilicaria aprina at Botany Bay (77°S latitude) in the Ross Sea region, continental Antarctica. Chlorophyll fluorescence parameters that allowed hydrated metabolic activity to be detected were recorded with a special fluorometer at 2- or 3-h intervals. Air and thallus temperatures and incident PPFD (photosynthetic photon flux density, μmol photon m⁻² s⁻¹) were also recorded at hourly intervals. Activity was extremely variable between months and years and, overall, lichen was active for 7% of the 28-month period. Spring snow cover often delayed the onset of activity. Whereas the period immediately after snow melt was often very productive, the later months, January to March, often showed low or no activity. Mean thallus temperature when active was just above zero degrees and much higher than the annual mean air temperature of −15 to −19°C. Because major snow melts occurred when incident radiation was high, the lichen was also subjected to very high PPFD when active, often more than 2,500 μmol photon m⁻² s⁻¹. The major environmental stress appeared to be high light rather than low temperatures, and the variability of early season snow fall means that prediction of activity will be very difficult.     

Extreme high lichen growth rates detected in recently deglaciated areas in Tierra del Fuego

The goals of this study were to accurately determine the annual growth rate of two key lichen species for lichenometric studies in Tierra del Fuego and to provide more information on recent glacial evolution in the southernmost mountain range of South America. The study site was located on recent moraines deposited in front of a terminus of Pia Glacier in the East Arm of Pia Bay, a fjord of the Beagle Channel. Lichenometric measurements were made of the maximum and minimum axes on the five largest thalli of Rhizocarpon geographicum and Placopsis perrugosa at selected localities in the recently deglaciated area. Average growth rates were estimated from dated surfaces to be 0.63 mm year⁻¹ for R. geographicum and of 9.0 mm year⁻¹ for P. perrugosa. However, maximum growth rate of individual thalli of P. perrugosa could be as high as about 20 mm year⁻¹ increase in diameter directly measured from comparison between pictures taken over a 2-year interval. Both species had an almost linear increase in diameter size with the age of the rock surfaces and the distance from the glacier. The rapid colonization and growth of the lichens is mirrored by the higher plants with ecesis for Nothofagus trees being estimated at 4 years and height growth elongation at 30 cm year⁻¹.     

Aldose reductase deficiency in mice protects from ragweed pollen extract (RWE)-induced allergic asthma

Background

Childhood hospitalization related to asthma remains at historically high levels, and its incidence is on the rise world-wide. Previously, we have demonstrated that aldose reductase (AR), a regulatory enzyme of polyol pathway, is a major mediator of allergen-induced asthma pathogenesis in mouse models. Here, using AR null (AR^-/-) mice we have investigated the effect of AR deficiency on the pathogenesis of ragweed pollen extract (RWE)-induced allergic asthma in mice and also examined the efficacy of enteral administration of highly specific AR inhibitor, fidarestat.

Methods

The wild type (WT) and AR^-/- mice were sensitized and challenged with RWE to induce allergic asthma. AR inhibitor, fidarestat was administered orally. Airway hyper-responsiveness was measured in unrestrained animals using whole body plethysmography. Mucin levels and Th2 cytokine in broncho-alveolar lavage (BAL) were determined using mouse anti-Muc5A/C ELISA kit and multiplex cytokine array, respectively. Eosinophils infiltration and goblet cells were assessed by H&E and periodic acid Schiff (PAS)-staining of formalin-fixed, paraffin-embedded lung sections. T regulatory cells were assessed in spleen derived CD4⁺CD25⁺ T cells population.

Results

Deficiency of AR in mice led to significantly decreased PENH, a marker of airway hyper-responsiveness, metaplasia of airway epithelial cells and mucus hyper-secretion following RWE-challenge. This was accompanied by a dramatic decrease in infiltration of eosinophils into sub-epithelium of lung as well as in BAL and release of Th2 cytokines in response to RWE-challenge of AR^-/- mice. Further, enteral administration of fidarestat significantly prevented eosinophils infiltration, airway hyper-responsiveness and also markedly increased population of T regulatory (CD4⁺CD25⁺FoxP3⁺) cells as compared to RWE-sensitized and challenged mice not treated with fidarestat.

Conclusion

Our results using AR^-/- mice strongly suggest the role of AR in allergic asthma pathogenesis and effectiveness of oral administration of AR inhibitor in RWE-induced asthma in mice supports the use of AR inhibitors in the treatment of allergic asthma.     

Giardia intestinalis escapes oxidative stress by colonizing the small intestine: A molecular hypothesis

Giardia intestinalis is the microaerophilic protozoon causing giardiasis, a common infectious intestinal disease. Giardia possesses an O(2) -scavenging activity likely essential for survival in the host. We report that Giardia trophozoites express the O(2) -detoxifying flavodiiron protein (FDP), detected by immunoblotting, and are able to reduce O(2) to H(2) O rapidly (～3 μM O(2) × min × 10(6) cells at 37 °C) and with high affinity (C(50) = 3.4 ± 0.7 μM O(2)). Following a short-term (minutes) exposure to H(2) O(2) ≥ 100 μM, the O(2) consumption by the parasites is irreversibly impaired, and the FDP undergoes a degradation, prevented by the proteasome-inhibitor MG132. Instead, H(2) O(2) does not cause degradation or inactivation of the isolated FDP. On the basis of the elevated susceptibility of Giardia to oxidative stress, we hypothesize that the parasite preferentially colonizes the small intestine since, compared with colon, it is characterized by a greater capacity for redox buffering and a lower propensity to oxidative stress.     

Laminar analysis of excitatory local circuits in vibrissal motor and sensory cortical areas

Rodents move their whiskers to locate and identify objects. Cortical areas involved in vibrissal somatosensation and sensorimotor integration include the vibrissal area of the primary motor cortex (vM1), primary somatosensory cortex (vS1; barrel cortex), and secondary somatosensory cortex (S2). We mapped local excitatory pathways in each area across all cortical layers using glutamate uncaging and laser scanning photostimulation. We analyzed these maps to derive laminar connectivity matrices describing the average strengths of pathways between individual neurons in different layers and between entire cortical layers. In vM1, the strongest projection was L2/3→L5. In vS1, strong projections were L2/3→L5 and L4→L3. L6 input and output were weak in both areas. In S2, L2/3→L5 exceeded the strength of the ascending L4→L3 projection, and local input to L6 was prominent. The most conserved pathways were L2/3→L5, and the most variable were L4→L2/3 and pathways involving L6. Local excitatory circuits in different cortical areas are organized around a prominent descending pathway from L2/3→L5, suggesting that sensory cortices are elaborations on a basic motor cortex-like plan.     

<Emphasis Type="Italic">Trichophyton rubrum</Emphasis> manipulates the innate immune functions of human keratinocytes

Evasion or subversion of host immune responses have been shown for a variety of microorganisms, and this might be the case for Trichophyton rubrum, the most common pathogenic fungus causing chronic dermatophytosis in humans. Keratinocytes, the main epidermal cells, have important roles as a first defense against microbial challenges in local immune reactions. Epidermal keratinocytes express several Toll-like receptors and produce host defense peptides, cytokines and chemokines in response to various stimuli. We analyzed the expression of Toll-Like receptor TLR2, TLR4, TLR6, and Human Beta Defensin (HBD)-1, HBD-2, Interleukin IL-1b and IL-8 production, when exposing primary keratinocyte cultures to T. rubrum. We observed changes in size and granularity of keratinocytes stimulated with either whole conidia or conidial homogenates compared to other treatments. Intact conidia decreased keratinocytes’ TLR2 and TLR6 expression without affecting that of TLR4, while conidial homogenates increased the expression of these three receptors. Interestingly, whole conidia decreased HBD-1 and HBD-2 production, whereas conidial homogenate increased it. No changes were observed in IL-1b and IL-8 production after stimulation with conidia or conidial homogenate. CONCLUSIONS. Our results suggest that: 1) Keratinocytes can recognize and respond to cell wall components of T. rubrum; 2) Viable intact conidia inhibit TLR-2 and TLR6 expression and decrease HBD-1 and HBD-2 production; 3) Conidial homogenate from T. rubrum increases the expression of TLR2, TLR4 and TLR6 and induces HBD-1 and HBD-2 production; 4) Therefore, innate immune functions of keratinocytes as the first level of local skin immunity are apparently manipulated by T. rubrum, likely to ensure its establishment, persistence and survival.     

Recording lifetime behavior and movement in an invertebrate model

Characterization of lifetime behavioral changes is essential for understanding aging and aging-related diseases. However, such studies are scarce partly due to the lack of efficient tools. Here we describe and provide proof of concept for a stereo vision system that classifies and sequentially records at an extremely fine scale six different behaviors (resting, micro-movement, walking, flying, feeding and drinking) and the within-cage (3D) location of individual tephritid fruit flies by time-of-day throughout their lives. Using flies fed on two different diets, full sugar-yeast and sugar-only diets, we report for the first time their behavioral changes throughout their lives at a high resolution. We have found that the daily activity peaks at the age of 15-20 days and then gradually declines with age for flies on both diets. However, the overall daily activity is higher for flies on sugar-only diet than those on the full diet. Flies on sugar-only diet show a stronger diurnal localization pattern with higher preference to staying on the top of the cage during the period of light-off when compared to flies on the full diet. Clustering analyses of age-specific behavior patterns reveal three distinct young, middle-aged and old clusters for flies on each of the two diets. The middle-aged groups for flies on sugar-only diet consist of much younger age groups when compared to flies on full diet. This technology provides research opportunities for using a behavioral informatics approach for understanding different ways in which behavior, movement, and aging in model organisms are mutually affecting.     

Are MYO1C and MYO1F associated with hearing loss?

The role of myosins in the pathogenesis of hearing loss is well established: five genes encoding unconventional myosins and two genes encoding nonmuscle conventional myosins have so far been described to be essential for normal auditory function and mutations in these genes associated with hearing impairment. To better understand the role of this gene family we performed a mutational screening on two candidate genes, MYO1C and MYO1F, analyzing hundreds of patients, affected by bilateral sensorineural hearing loss and coming from different European countries. This research activity led to the identification of 6 heterozygous missense mutations in MYO1C and additional 5 heterozygous missense mutations in MYO1F. Homology modelling suggests that some of these mutations could have a potential influence on the structure of the ATP binding site and could probably affect the ATPase activity or the actin binding process of both myosins. This study suggests a role of the above mentioned myosin genes in the pathogenesis of hearing loss.     

Ferritin heavy chain is the host factor responsible for HCV-induced inhibition of apoB-100 production and is required for efficient viral infection

Hepatic fat export occurs by apolipoprotein B-100-containing lipoprotein production, whereas impaired production leads to liver steatosis. Hepatitis C virus (HCV) infection is associated to dysregulation of apoB-100 secretion and steatosis; however, the molecular mechanism by which HCV affects the apoB-100 secretion is not understood. Here, combining quantitative proteomics and computational biology, we propose ferritin heavy chain (Fth) as being the cellular determinant of apoB-100 production inhibition. By means of molecular analyses, we found that HCV nonstructural proteins and NS5A appear to be sufficient for inducing Fth up-regulation. Fth in turn was found to inhibit apoB-100 secretion leading to increased intracellular degradation via proteasome. Notably, intracellular Fth down-regulation by siRNA restores apoB-100 secretion. The inverse correlation between ferritin and plasma apoB-100 concentrations was also found in JFH-1 HCV cell culture systems (HCVcc) and HCV-infected patients. Finally, Fth expression was found to be required for robust HCV infection. These observations provide a further molecular explanation for the onset of liver steatosis and allow for hypothesizing on new therapeutic and antiviral strategies.