Understanding the Low Photosynthetic Rates of Sun and Shade Coffee Leaves: Bridging the Gap on the Relative Roles of Hydraulic,Diffusive and Biochemical Constraints to Photosynthesis

It has long been held that the low photosynthetic rates (A) of coffee leaves are largely associated with diffusive constraints to photosynthesis. However, the relative limitations of the stomata and mesophyll to the overall diffusional constraints to photosynthesis, as well as the coordination of leaf hydraulics with photosynthetic limitations, remain to be fully elucidated in coffee. Whether the low actual A under ambient CO₂ concentrations is associated with the kinetic properties of Rubisco and high (photo)respiration rates also remains elusive. Here, we provide a holistic analysis to understand the causes associated with low A by measuring a variety of key anatomical/hydraulic and photosynthetic traits in sun- and shade-grown coffee plants. We demonstrate that leaf hydraulic architecture imposes a major constraint on the maximisation of the photosynthetic gas exchange of coffee leaves. Regardless of the light treatments, A was mainly limited by stomatal factors followed by similar limitations associated with the mesophyll and biochemical constraints. No evidence of an inefficient Rubisco was found; rather, we propose that coffee Rubisco is well tuned for operating at low chloroplastic CO₂ concentrations. Finally, we contend that large diffusive resistance should lead to large CO₂ drawdown from the intercellular airspaces to the sites of carboxylation, thus favouring the occurrence of relatively high photorespiration rates, which ultimately leads to further limitations to A.     

Endogenous Opioid Antagonism in Physiological Experimental Pain Models: A Systematic Review

Opioid antagonists are pharmacological tools applied as an indirect measure to detect activation of the endogenous opioid system (EOS) in experimental pain models. The objective of this systematic review was to examine the effect of mu-opioid-receptor (MOR) antagonists in placebo-controlled, double-blind studies using ʻinhibitoryʼ or ʻsensitizingʼ, physiological test paradigms in healthy human subjects. The databases PubMed and Embase were searched according to predefined criteria. Out of a total of 2,142 records, 63 studies (1,477 subjects [male/female ratio = 1.5]) were considered relevant. Twenty-five studies utilized ʻinhibitoryʼ test paradigms (ITP) and 38 studies utilized ʻsensitizingʼ test paradigms (STP). The ITP-studies were characterized as conditioning modulation models (22 studies) and repetitive transcranial magnetic stimulation models (rTMS; 3 studies), and, the STP-studies as secondary hyperalgesia models (6 studies), ʻpainʼ models (25 studies), summation models (2 studies), nociceptive reflex models (3 studies) and miscellaneous models (2 studies). A consistent reversal of analgesia by a MOR-antagonist was demonstrated in 10 of the 25 ITP-studies, including stress-induced analgesia and rTMS. In the remaining 14 conditioning modulation studies either absence of effects or ambiguous effects by MOR-antagonists, were observed. In the STP-studies, no effect of the opioid-blockade could be demonstrated in 5 out of 6 secondary hyperalgesia studies. The direction of MOR-antagonist dependent effects upon pain ratings, threshold assessments and somatosensory evoked potentials (SSEP), did not appear consistent in 28 out of 32 ʻpainʼ model studies. In conclusion, only in 2 experimental human pain models, i.e., stress-induced analgesia and rTMS, administration of MOR-antagonist demonstrated a consistent effect, presumably mediated by an EOS-dependent mechanisms of analgesia and hyperalgesia.     

Fungal Biodegradation and Detoxification of Cork Boiling Wastewaters

The ability of several fungal strains to degrade and to detoxify cork boiling wastewaters was investigated. The fungal strains used in this work were Sporothrix sp., Trichoderma koningii, Chrysonilia sitophila and Penicillium glabrum isolated from cork bark as well as Fusarium flocciferum and Phanerochaete chrysosporium. The results obtained in the degradation experiments carried out with each fungus showed that all fungi display similar abilities, with a chemical oxygen demand reduction of 54.2 % (± 4.7 %) attained within five days of incubation. F. flocciferum presented the highest value for the reduction of chemical oxygen demand of 62 %. In addition, a rise in pH values of around 3 units was detected with all the strains, except for Penicillium glabrum. Toxicity tests performed on Vibrio fischeri revealed that fungal treatment of the wastewaters causes the complete loss of toxicity in the cases of Sporothrix sp., T. koningii, P. chrysosporium and F. flocciferum. The other two tested strains were also able to detoxify the raw wastewaters, causing a ten‐fold decrease in toxicity. The results obtained in sequential biodegradation experiments with different pairs of fungi showed that although the increment in the COD reduction did not exceed 10 %, an important reduction in toxicity and a pH rise were attained.     

Modification of a Reaction Vessel for the Determination of Total Mercury in Hair by Cold Vapor Atomic Absorption Spectrometry

A classical cold vapor atomic absorption spectrometric (CVAAS) method for the determination of total mercury in blood has been previously adapted for application to samples of human hair. The reaction vessel specified in the original adaptation was, however, large and difficult to use with small hair samples. In the present study, the reaction vessel has been modified and reduced in size and the protocols have been optimized in order to provide an analytical method that is more efficient, less time-consuming, and gives lower blank values than the original adaptation. The optimized method was validated by multiple, independent, replicated assays of certified reference hair samples, and the mean recovery obtained (98.7%) indicated an efficient performance of the digestion and detection processes. The method was applied to the assay of 144 hair samples derived from populations that had or had not been exposed to mercury from environmental sources. The results from all of the samples analyzed were consistent with those published previously for similar samples.     

Manipulating vibratory devices’ orientation and position enhances proprioceptive disturbance during upright stance

We tested local vibration effects during upright standing considering: (i) the orientation of vibratory devices in relation to muscle fibres; (ii) the muscle region stimulated; and (iii) the number of stimulation spots. Results showed a higher balance disturbance with vibration devices oriented parallel to triceps surae muscle fibres. The single stimulation of the proximal region of the tibialis anterior muscle belly induces the same proprioceptive disturbance as stimulating multiple regions simultaneously.     

Analysis of the ergosterol biosynthesis pathway cloning,molecular characterization and phylogeny of lanosterol 14 α-demethylase (ERG11) gene of Moniliophthora perniciosa

The phytopathogenic fungus Moniliophthora perniciosa (Stahel) Aime & Philips-Mora, causal agent of witches’ broom disease of cocoa, causes countless damage to cocoa production in Brazil. Molecular studies have attempted to identify genes that play important roles in fungal survival and virulence. In this study, sequences deposited in the M. perniciosa Genome Sequencing Project database were analyzed to identify potential biological targets. For the first time, the ergosterol biosynthetic pathway in M. perniciosa was studied and the lanosterol 14α-demethylase gene (ERG11) that encodes the main enzyme of this pathway and is a target for fungicides was cloned, characterized molecularly and its phylogeny analyzed. ERG11 genomic DNA and cDNA were characterized and sequence analysis of the ERG11 protein identified highly conserved domains typical of this enzyme, such as SRS1, SRS4, EXXR and the heme-binding region (HBR). Comparison of the protein sequences and phylogenetic analysis revealed that the M. perniciosa enzyme was most closely related to that of Coprinopsis cinerea.     

A New theraphosid Spider Toxin Causes Early Insect Cell Death by Necrosis When Expressed In Vitro during Recombinant Baculovirus Infection

Baculoviruses are the most studied insect viruses in the world and are used for biological control of agricultural and forest insect pests. They are also used as versatile vectors for expression of heterologous proteins. One of the major problems of their use as biopesticides is their slow speed to kill insects. Thus, to address this shortcoming, insect-specific neurotoxins from arachnids have been introduced into the baculovirus genome solely aiming to improve its virulence. In this work, an insecticide-like toxin gene was obtained from a cDNA derived from the venom glands of the theraphosid spider Brachypelma albiceps. The mature form of the peptide toxin (called Ba3) has a high content of basic amino acid residues, potential for three possible disulfide bonds, and a predicted three-stranded β-sheetDifferent constructions of the gene were engineered for recombinant baculovirus Autographa californica multiple nuclepolyhedrovirus (AcMNPV) expression. Five different forms of Ba3 were assessed; (1) the full-length sequence, (2) the pro-peptide and mature region, (3) only the mature region, and the mature region fused to an (4) insect or a (5) virus-derived signal peptide were inserted separately into the genome of the baculovirus. All the recombinant viruses induced cell death by necrosis earlier in infection relative to a control virus lacking the toxin gene. However, the recombinant virus containing the mature portion of the toxin gene induced a faster cell death than the other recombinants. We found that the toxin construct with the signal peptide and/or pro-peptide regions delayed the necrosis phenotype. When infected cells were subjected to ultrastructural analysis, the cells showed loss of plasma membrane integrity and structural changes in mitochondria before death. Our results suggest this use of baculovirus is a potential tool to help understand or to identify the effect of insect-specific toxic peptides when produced during infection of insect cells.     

DROSOPHILA S2 cell culture in a WAVE Bioreactor: potential for scaling up the production of the recombinant rabies virus glycoprotein

Applied Microbiology and Biotechnology - The transmembrane rabies virus glycoprotein (RVGP) is the main antigen of vaccine formulations used around the world to prevent rabies, the most lethal...