Titanium and iron titanium oxide nanoparticles in antennae of the migratory ant <Emphasis Type="Italic">Pachycondyla marginata</Emphasis>: an alternative magnetic sensor for magnetoreception?

The most accepted hypothesis of magnetoreception for social insects is the ferromagnetic hypothesis which assumes the presence of magnetic material as a sensor coupled to sensitive structures that transmit the geomagnetic field information to the nervous system. As magnetite is the most common magnetic material observed in living beings, it has been suggested as basic constituent of the magnetoreception system. Antennae and head have been pointed as possible magnetosensor organs in social insects as ants, bees and termites. Samples of three antenna joints: head-scape, scape-pedicel and pedicel-third segment joints were embedded in epoxi resin, ultrathin sectioned and analyzed by transmission electron microscopy. Selected area electron diffraction patterns and X-ray energy dispersive spectroscopy were obtained to identify the nanoparticle compound. Besides iron oxides, for the first time, nanoparticles containing titanium have been identified surrounded by tissue in the antennae of ants. Given their dimension and related magnetic characteristics, these nanoparticles are discussed as being part of the magnetosensor system.     

Climate change fingerprints in recent European plant phenology

A paper published in Global Change Biology in 2006 revealed that phenological responses in 1971–2000 matched the warming pattern in Europe, but a lack of chilling and adaptation in farming may have reversed these findings. Therefore, for 1951–2018 in a corresponding data set, we determined changes as linear trends and analysed their variation by plant traits/groups, across season and time as well as their attribution to warming following IPCC methodology. Although spring and summer phases in wild plants advanced less (maximum advances in 1978–2007), more (~90%) and more significant (~60%) negative trends were present, being stronger in early spring, at higher elevations, but smaller for nonwoody insect‐pollinated species. These trends were strongly attributable to winter and spring warming. Findings for crop spring phases were similar, but were less pronounced. There were clearer and attributable signs for a delayed senescence in response to winter and spring warming. These changes resulted in a longer growing season, but a constant generative period in wild plants and a shortened one in agricultural crops. Phenology determined by farmers’ decisions differed noticeably from the purely climatic driven phases with smaller percentages of advancing (~75%) trends, but farmers’ spring activities were the only group with reinforced advancement, suggesting adaptation. Trends in farmers’ spring and summer activities were very likely/likely associated with the warming pattern. In contrast, the advance in autumn farming phases was significantly associated with below average summer warming. Thus, under ongoing climate change with decreased chilling the advancing phenology in spring and summer is still attributable to warming; even the farmers’ activities in these seasons mirror, to a lesser extent, the warming. Our findings point to adaptation to climate change in agriculture and reveal diverse implications for terrestrial ecosystems; the strong attribution supports the necessary mediation of warming impacts to the general public.     

HIV Viremia and T-Cell Activation Differentially Affect the Performance of Glomerular Filtration Rate Equations Based on Creatinine and Cystatin C

Background

Serum creatinine and cystatin C are used as markers of glomerular filtration rate (GFR). The performance of these GFR markers relative to exogenously measured GFR (mGFR) in HIV-positive individuals is not well established.

Methods

We assessed the performance of the chronic kidney disease epidemiology collaboration equations based on serum concentrations of creatinine (eGFR_cr), cystatin C (eGFR_cys) and both biomarkers combined (eGFR_cr-cys) in 187 HIV-positive and 98 HIV-negative participants. Measured GFR was calculated by plasma iohexol clearance. Bias and accuracy were defined as the difference between eGFR and mGFR and the percentage of eGFR observations within 30% of mGFR, respectively. Activated CD4 and CD8 T-cells (CD38+ HLA-DR+) were measured by flow cytometry.

Results

The median mGFR was >100 ml/min/1.73 m² in both groups. All equations tended to be less accurate in HIV-positive than in HIV-negative subjects, with eGFR_cr-cys being the most accurate overall. In the HIV-positive group, eGFR_cys was significantly less accurate and more biased than eGFR_cr and eGFR_{cr_cys}. Additionally eGFR_cys bias and accuracy were strongly associated with use of antiretroviral therapy, HIV RNA suppression, and percentages of activated CD4 or CD8 T-cells. Hepatitis C seropositivity was associated with larger eGFR_cys bias in both HIV-positive and HIV-negative groups. In contrast, eGFR_cr accuracy and bias were not associated with HIV-related factors, T-cell activation, or hepatitis C.

Conclusions

The performance of eGFR_cys relative to mGFR was strongly correlated with HIV treatment factors and markers of T-cell activation, which may limit its usefulness as a GFR marker in this population.     

Biochemical markers of vascular calcification in elderly hemodialysis patients

The increased vascular calcification, cardiovascular morbidity, and mortality in chronic kidney disease (CKD) patients has been associated with disturbances in mineral-bone metabolism. In order to determine markers of the vascular calcification frequently observed in these patients, blood samples of elderly male and female hemodialysis CKD patients were used to measure serum levels of: osteoprotegerin (OPG), total soluble receptor activator of nuclear factor-κB ligand (sRANKL), and fetuin-A by enzyme immunoassay; tartrate-resistant acid phosphatase (TRACP-5b), and bone-specific alkaline phosphatase (BAP) by immunoenzymometric assay; osteocalcin (OC) by ELISA; iPTH by immunoradiometric assay; 25(OH)D₃ and 1,25(OH)₂D₃, by I¹²⁵ radioimmunoassay; and calcium and phosphorus by photometric assay. Serum OPG, BAP, iPTH, phosphorus, and OC levels were higher and serum 25(OH)D₃, 1,25(OH)₂D₃, and fetuin-A levels lower in both male and female CKD patients than in their respective controls. Our results indicate that the bone formation and resorption parameters are altered in elderly male and female hemodialysis CKD patients. These changes may lead to vascular calcifications and cardiovascular complications, given that elevated OPG and OC levels and reduced fetuin-A levels are associated with cardiovascular events.     

Bax induces cytochrome c release by multiple mechanisms in mitochondria from MCF7 cells

Bax, a pro-apoptotic member of the Bcl-2 family of proteins has the ability to form transmembrane pores large enough to allow cytochrome c (Cyt c) release, as well as to activate the mitochondrial permeability transition pore (mPTP); however, no differential study has been conducted to clarify which one of these mechanisms predominates over the other in the same system. In the present study, we treated isolated mitochondria from MCF7 cells with recombinant protein Bax and tested the efficacy of the mPTP inhibitor cyclosporin A (CsA) and of the Bax channel blocker (Bcb) to inhibit cytochrome c release. We also, induced apoptosis in MCF7 cell cultures with TNF-α plus cycloheximide to determine the effect of such compounds in apoptosis induction via mPTP or Bax oligomerization. Cytochrome c release was totally prevented by CsA and partially by Bcb when apoptosis was induced with recombinant Bax in isolated mitochondria from MCF7 cells. CsA increased the number of living cells in cell culture, as compared with the effect of Bax channel blocker. These results indicate that mPTP activation is the predominant pathway for Bax-induced cytochrome c release from MCF7 mitochondria and for apoptosis induction in the whole cell.     

Substitutions at the opening of the Rubisco central solvent channel affect holoenzyme stability and CO2/O2 specificity but not activation by Rubisco activase

Ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) catalyzes the initial step of carbon metabolism in photosynthesis. The holoenzyme comprises eight large subunits, arranged as a tetramer of dimers around a central solvent channel that defines a fourfold axis of symmetry, and eight small subunits, arranged as two tetramers at the poles of the axis. The phylogenetically divergent small-subunit loops between β-strands A and B form the entrance to the solvent channel. In the green alga Chlamydomonas reinhardtii, Ile-58 from each of the four small-subunit βA–βB loops defines the minimal diameter of the channel opening. To understand the role of the central solvent channel in Rubisco function, directed mutagenesis and transformation of Chlamydomonas were employed to replace Ile-58 with Ala, Lys, Glu, Trp, or three Trp residues (I58W3) to close the entrance to the channel. The I58E, I58K, and I58W substitutions caused only small decreases in photosynthetic growth at 25 and 35 °C, whereas I58W3 had a substantial effect at both temperatures. The mutant enzymes had decreased carboxylation rates, but the I58W3 enzyme had decreases in both carboxylation and CO₂/O₂ specificity. The I58E, I58W, and I58W3 enzymes were inactivated at lower temperatures than wild-type Rubisco, and were degraded at slower rates under oxidative stress. However, these mutant enzymes were activated by Rubisco activase at normal rates, indicating that the structural transition required for carboxylation is not affected by altering the solvent channel opening. Structural dynamics alone may not be responsible for these distant effects on the Rubisco active site.     

Further Thymol Derivatives from Ageratina cylindrica

From the leaves of Ageratina cylindrica, in addition to the described [(2S)‐2‐{4‐formyl‐5‐hydroxy‐2‐[(2‐methylpropanoyl)oxy]phenyl}oxiran‐2‐yl]methyl benzoate (cylindrinol A, 8 ), seven new thymol derivatives were isolated and named cylindrinols B – H ( 1 – 7 ). The structures of these compounds were established as (2‐{4‐(hydroxymethyl)‐2‐[(2‐methylpropanoyl)oxy]phenyl}oxiran‐2‐yl)methyl benzoate ( 1 ), (2‐{4‐formyl‐2‐[(2‐methylpropanoyl)oxy]phenyl}oxiran‐2‐yl)methyl benzoate ( 2 ), (2‐{4‐[(acetyloxy)methyl]‐2‐[(2‐methylpropanoyl)oxy]phenyl}oxiran‐2‐yl)methyl benzoate ( 3 ), [2‐(2‐[(2‐methylpropanoyl)oxy]‐4‐{[(2‐methylpropanoyl)oxy]methyl}phenyl)oxiran‐2‐yl]methyl benzoate ( 4 ), [2‐(5‐hydroxy‐2‐[(2‐methylpropanoyl)oxy]‐4‐{[(2‐methylpropanoyl)oxy]methyl}phenyl)oxiran‐2‐yl]methyl benzoate ( 5 ), 2‐{4‐(hydroxymethyl)‐2‐[(2‐methylpropanoyl)oxy]phenyl}prop‐2‐en‐1‐yl benzoate ( 6 ), and 2‐hydroxy‐2‐[2‐hydroxy‐4‐(hydroxymethyl)‐phenyl]‐3‐[(2‐methylpropanoyl)oxy]propyl benzoate ( 7 ), by spectroscopic means. Compounds 1 showed moderate antiprotozoal activity on both protozoa. Compounds 4 and 5 showed selectivity on Giardia lamblia trophozoites. All isolated compounds were less active than two antiprotozoal drugs, metronidazole and emetine, used as positive controls. Compound 5 exhibited a high inhibitory effect on hyperpropulsive movement of the small intestine in rats; its effect was best than loperamide, antidiarrheal drug used as a positive control.     

Synthesis of a green polyurethane foam from a biopolyol obtained by enzymatic glycerolysis and its use for immobilization of lipase NS-40116

The use of green sources for materials synthesis has gained popularity in recent years. This work investigated the immobilization of lipase NS-40116 (Thermomyces lanuginosus lipase) in polyurethane foam (PUF) using a biopolyol obtained through the enzymatic glycerolysis between castor oil and glycerol, catalyzed by the commercial lipase Novozym 435 for the PUF formation. The reaction was performed to obtain biopolyol resulting in the conversion of 64% in mono- and diacylglycerol, promoting the efficient use of the reaction product as biopolyol to obtain polyurethane foam. The enzymatic derivative with immobilized lipase NS-40116 presented apparent density of 0.19 ± 0.03 g/cm³ and an immobilization yield was 94 ± 4%. Free and immobilized lipase NS-40116 were characterized in different solvents (methanol, ethanol, and propanol), temperatures (20, 40, 60 and 80 °C), pH (3, 5, 7, 9 and 11) and presence of ions Na⁺, Mg⁺⁺, and Ca⁺⁺. The support provided higher stability to the enzyme, mainly when subjected to acid pH (free lipase lost 80% of relative activity after 360 h of contact, when the enzymatic derivative lost around 22%) and high-temperature free lipase lost 50% of relative activity, while the immobilized remained 95%. The enzymatic derivative was also used for esterification reactions and conversions around 66% in fatty acid methyl esters, using abdominal chicken fat as feedstock, were obtained in the first use, maintaining this high conversion until the fourth reuse, proving that the support obtained using environmentally friendly techniques is applicable.