Thermoregulatory behavior and oxygen consumption of Octopus mimus paralarvae: The effect of age

Octopus mimus is an important cephalopod species in the coastal zone of Peru and Chile that is exposed to temperature variations from time to time due to El Niño/Southern Oscillation (ENSO) episodes when surface temperatures can reach 24 °C, 6 °C above typical temperatures in their habitat. The relationships between temperature and food availability are important factors that determine the recruitment of juveniles into the O. mimus population. The present study was to evaluate the relationship between thermoregulatory behavior and the age of paralarvae (summer population) to determine whether changes in this behavior occur during internal yolk consumption, making larvae more vulnerable to environmental temperature change. Oxygen consumption of paralarvae when 1–4 d old was determined to establish if respiration could be used to monitor the physiological changes that occur during yolk consumption. Horizontal thermal selection (17–30 °C), critical thermal maxima (CTMax), minima (CTMin), and oxygen consumption experiments were conducted with fasting paralarvae 1–4 d old at 20 °C. Preferred temperatures were dependent on the age of O. mimus paralarvae. One day old paralarvae selected a temperature 1.1 °C (23·4 °C) higher than 2 – 4 d old paralarvae (22·3 °C). The CTMax of paralarvae increased with age with values of 31·9±1.1 °C in 1-d-olds and 33·4±0.3 to 4-d-olds. CTMin also changed with age with low values in 2-d-old paralarvae (9.1±1·3 °C) and 11·9±0·9 °C in 4-d-old animals. The temperature tolerance range of paralarvae was age-dependent (TTD=difference between CTMax and CTMin) with higher values in 2 and 3 d old paralarvae (25–26 °C) as compared to 1 d old (23·1 °C) and 4 d old animals (22.7 °C). Oxygen consumption was not affected by the age of paralarvae, suggesting that mechanisms exist that compensate their metabloism until at least 4 d of age. The temperature tolerance range of a planktonic paralarvae of octopus species is presented for the first time. This range was dependent on the age of paralarvae, and so rendered the paralarvae more vunerable to a combination of high temperature and food deprivation during first days of life. Results in the present study provide evidence that O. mimus could be under ecological pressure if a climate change causes increased or decreased temperatures into their distribution range.     

Histamine H1 and Endothelin ETB Receptors Mediate Phospholipase D Stimulation in Rat Brain Hippocampal Slices

Abstract: Different neurotransmitter receptor agonists [carbachol, serotonin, noradrenaline, histamine, endothelin-1, and trans -(1 S ,3 R )-aminocyclopentyl-1,3-dicarboxylic acid ( trans -ACPD)], known as stimuli of phospholipase C in brain tissue, were tested for phospholipase D stimulation in [³²P]P_i-prelabeled rat brain cortical and hippocampal slices. The accumulation of [³²P]phosphatidylethanol was measured as an index of phospholipase D-catalyzed transphosphatidylation in the presence of ethanol. Among the six neurotransmitter receptor agonists tested, only noradrenaline, histamine, endothelin-1, and trans -ACPD stimulated phospholipase D in hippocampus and cortex, an effect that was strictly dependent of the presence of millimolar extracellular calcium concentrations. The effect of histamine (EC₅₀ 18 µ M ) was inhibited by the H₁ receptor antagonist mepyramine with a K _i constant of 0.7 n M and was resistant to H₂ and H₃ receptor antagonists (ranitidine and tioperamide, respectively). Endothelin-1-stimulated phospholipase D (EC₅₀ 44 n M ) was not blocked by BQ-123, a specific antagonist of the ET_A receptor. Endothelin-3 and the specific ET_B receptor agonist safarotoxin 6c were also able to stimulate phospholipase D with efficacies similar to that of endothelin-1, and EC₅₀ values of 16 and 3 n M , respectively. These results show that histamine and endothelin-1 stimulate phospholipase D in rat brain through H₁ and ET_B receptors, respectively.     

Targeting of a T cell agonist peptide to lysosomes by DNA vaccination induces tolerance in the nonobese diabetic mouse

CD4 T cells are crucial effectors in the pathology of type 1 diabetes (T1D). Successful therapeutic interventions for prevention and cure of T1D in humans are still elusive. Recent research efforts have focused on the manipulation of T cells by treatment with DNA. In this paper, we studied the effects of a DNA treatment strategy designed to target antigenic peptides to the lysosomal compartment on a monospecific T cell population termed 2.5mi(+) T cells that shares reactivity with the diabetogenic T cell clone BDC-2.5 in the NOD mouse. MHC class II tetramer analysis showed that repeated administrations were necessary to expand 2.5mi(+) T cells in vivo. This expansion was independent of Ag presentation by B cells. A single peptide epitope was sufficient to induce protection against T1D, which was not due to Ag-specific T cell anergy. Typical Th2 cytokines such as IL-10 or IL-4 were undetectable in 2.5mi(+) T cells, arguing against a mechanism of immune deviation. Instead, the expanded 2.5mi(+) T cell population produced IFN-γ similar to 2.5mi(+) T cells from naive mice. Protection against T1D by DNA treatment was completely lost in NOD.CD28(-/-) mice which are largely deficient of natural regulatory T cells (Treg). Although Ag-specific Foxp3(+) Treg did not expand in response to DNA treatment, diabetes onset was delayed in Treg-reconstituted and DNA-treated NOD.SCID mice. These observations provide evidence for a Treg-mediated protective mechanism that is independent of the expansion or de novo generation of Ag-specific Treg.     

Metabolism of Plant Polysaccharides by Leucoagaricus gongylophorus, the Symbiotic Fungus of the Leaf-Cutting Ant Atta sexdens L.

Atta sexdens L. ants feed on the fungus they cultivate on cut leaves inside their nests. The fungus, Leucoagaricus gongylophorus, metabolizes plant polysaccharides, such as xylan, starch, pectin, and cellulose, mediating assimilation of these compounds by the ants. This metabolic integration may be an important part of the ant-fungus symbiosis, and it involves primarily xylan and starch, both of which support rapid fungal growth. Cellulose seems to be less important for symbiont nutrition, since it is poorly degraded and assimilated by the fungus. Pectin is rapidly degraded but slowly assimilated by L. gongylophorus, and its degradation may occur so that the fungus can more easily access other polysaccharides in the leaves.     

Microhabitat amelioration and reduced competition among understorey plants as drivers of facilitation across environmental gradients: Towards a unifying framework

Studies of facilitative interactions as drivers of plant richness along environmental gradients often assume the existence of an overarching stress gradient that equally affects the performance of all the species in a given community. However, co-existing species differ in their ecophysiological adaptations, and do not experience the same stress level under particular environmental conditions. Moreover, these studies assume a unimodal relationship between richness and biomass, which is not as general as previously thought. We ignored these assumptions to assess changes in plant–plant interactions and their effect on local species richness across environmental gradients in semi-arid areas of Spain and Australia. We aimed to understand the relative importance of direct (microhabitat amelioration) and indirect (changes in the competitive relationships among the understorey species: niche segregation, competitive exclusion or intransitivity) mechanisms that might underlie the effects of nurse plants on local species richness. By jointly studying these direct and indirect mechanisms using a unifying framework, we found that nurse plants (trees, shrubs and tussock grasses) increased local richness not only by expanding the niche of neighbouring species but also by increasing niche segregation among them, though the latter was not important in all cases. The outcome of the competition-facilitation continuum varied depending on the study area, likely because the different types of stress gradient considered. When driven by both rainfall and temperature, or rainfall alone, the community-wide importance of nurse plants remained constant (Spanish sites), or showed a unimodal relationship along the gradient (Australian sites). This study expands our understanding of the relative roles of plant–plant interactions and environmental conditions as drivers of local species richness in semi-arid environments. The results can also be used to refine predictions about the response of plant communities to environmental change, and to clarify the relative importance of biotic interactions as drivers of such responses.     

Helicobacter pylori antimicrobial resistance in a pediatric population

Background

The increasing prevalence of Helicobacter pylori (H. pylori) antimicrobial resistance, primarily for clarithromycin decreases the success of treatment. The aim of this study is to determine the local pattern of first‐line antimicrobials resistance and the eradication rate.

Material and Methods

Prospective cohort study of H. pylori infected patients (positive histological or cultural exams) treated at Centro Materno‐Infantil do Norte from January of 2013 to October of 2017. Susceptibility to 4 antibiotics: amoxicilin, metronidazole, clarithromycin, and levofloxacin were analyzed by E‐test (phenotypic resistance). The E‐test was chosen because it is simple and cost‐effective for routine susceptibility testing. Point mutations that confer clarithromycin resistance were surveyed (genotypic resistance). Eradication of H. pylori infection was defined by a negative urea breath test or fecal antigen 6‐8 weeks after the end of treatment.

Results

Of a total of 74 H. pylori infected patients, 16 were excluded because they had previous H. pylori treatment or severe systemic disease. Median age of infection cases was 15 years (3‐17 years). Eradication regimen used in all patients combined the use of 3 antibiotics (amoxicillin and metronidazole or clarithromycin) and proton pump inibhitor for 14 days and was tailored according antimicrobial susceptibility. 79.5% of the patients completed the treatment. The resistance rate for metronidazole and clarithromycin was 3.3% and 23.3%, respectively. There was no resistance for amoxicilin and levofloxacin. The rate of genotypic resistance to clarithromycin was 37.2%. The eradication rate was 97.8%.

Conclusions

The authors found a high resistance rate of H. pylori for clarithromycin in this northern portuguese pediatric center. This factor should determine a change in local current treatment, contraindicating the use of clarithromycin as a first‐line treatment for H. pylori infection in children. The high eradication rate maybe explained for the eradication treatment tailored according antimicrobial susceptibility.     

Modulation of Higher-Order Olfaction Components on Executive Functions in Humans

The prefrontal (PFC) and orbitofrontal cortex (OFC) appear to be associated with both executive functions and olfaction. However, there is little data relating olfactory processing and executive functions in humans. The present study aimed at exploring the role of olfaction on executive functioning, making a distinction between primary and more cognitive aspects of olfaction. Three executive tasks of similar difficulty were used. One was used to assess hot executive functions (Iowa Gambling Task-IGT), and two as a measure of cold executive functioning (Stroop Colour and Word Test-SCWT and Wisconsin Card Sorting Test-WCST). Sixty two healthy participants were included: 31 with normosmia and 31 with hyposmia. Olfactory abilities were assessed using the ‘‘Sniffin’ Sticks’’ test and the olfactory threshold, odour discrimination and odour identification measures were obtained. All participants were female, aged between 18 and 60. Results showed that participants with hyposmia displayed worse performance in decision making (IGT; Cohen’s-d = 0.91) and cognitive flexibility (WCST; Cohen’s-d between 0.54 and 0.68) compared to those with normosmia. Multiple regression adjusted by the covariates participants’ age and education level showed a positive association between odour identification and the cognitive inhibition response (SCWT-interference; Beta = 0.29; p = .034). The odour discrimination capacity was not a predictor of the cognitive executive performance. Our results suggest that both hot and cold executive functions seem to be associated with higher-order olfactory functioning in humans. These results robustly support the hypothesis that olfaction and executive measures have a common neural substrate in PFC and OFC, and suggest that olfaction might be a reliable cognitive marker in psychiatric and neurologic disorders.     

Unfolding of trp repressor studied using fluorescence spectroscopic techniques.

The unfolding properties of the trp repressor of Escherichia coli have been studied using a number of different time-resolved and steady-state fluorescence approaches. Denaturation by urea was monitored by the average fluorescence emission energy of the intrinsic tryptophan residues of the repressor. These data were consistent with a two-state transition from dimer to unfolded monomer with a free energy of unfolding of 19.2 kcal/mol. The frequency response profiles of the fluorescence emission brought to light subtle urea-induced modifications of the intrinsic tryptophan decay parameters both preceding and following the main unfolding transition. The increase of lifetime induced by urea required higher concentrations of urea than the increase in the total intensity described by Gittelman and Matthews [(1990) Biochemistry 29, 7011]. This indicates that the intensity increase has both dynamic and static origins. To assess the effect of tryptophan binding upon repressor stability, and to determine whether repressor oligomerization would be detectable in an unfolding experiment, we examined denaturation profiles of repressor labeled with the long-lived fluorescence probe 5-(dimethylamino)naphthalene-1-sulfonyl (DNS), by monitoring the average rotational correlation time of the probe. These experiments revealed a protein concentration dependent transition at low urea concentrations. This transition was promoted by tryptophan binding. We ascribe this transition to urea-induced dissociation of repressor tetramers. The main unfolding transition of the dimer to unfolded monomer was also observable using this technique, and the free energies associated with this transition were 18.3 kcal/mol in the absence of tryptophan and 24.1 kcal/mol in its presence, demonstrating that co-repressor binding stabilizes the repressor dimer against denaturation.(ABSTRACT TRUNCATED AT 250 WORDS)     

Hyperbolic Modeling of Starburst Dendrimers

Starburst dendrimers are highly branched oligomers. A rigid dendritic hydrocarbon, C₁₁₃₄H₁₁₄₆, has recently been synthesized. It consists of 94 phenylacetylene units displayed in a self-similar two-dimensional skeleton isomorphous to the three-coordinated Bethe lattice. The three-dimensional representation of phenylacetylene dendrimer shows a globular architecture with large voids and niches in its interior, characteristic of hyperbolic surfaces. This work investigates the geometrical scaling behavior of this starburst dendrimer using the symmetry properties of a Bethe lattice embedded in the hyperbolic plane. The results for C₁₁₃₄H₁₁₄₆ provide its density profile and an upper bound for its macromolecular size. This revised version was published online in June 2006 with corrections to the Cover Date.