Simultaneous purification and characterization of aspartate aminotransferase isoenzymes from chicken liver

Cytosolic and mitochondrial isoenzymes of aspartate aminotransferase (EC 2.6.1.1) were purified to homogeneity from chicken liver, without previous fractionation of the subcellular components. The procedure includes initial heat treatment and ammonium sulfate fractionation. The two isoenzymes can then be separated by a DEAE-Sepharose chromatography using a linear gradient of L-aspartate (reaction substrate). The separated fractions can be further purified by a parallel step with HA-Ultrogel prior to octyl-Sepharose (c-AAT) and CM-Sepharose (m-AAT) chromatographies. Michaelis constants, pI values, inhibition by adipate and subforms generation with time were studied for both isoenzymes.     

Biochemical properties of 1-aminocyclopropane-1-carboxylate N-malonyltransferase activity from early growing embryonic axes of chick-pea (Cicer arietinum L.) seeds

In the present work, certain biochemical characteristics ofthe enzyme 1-aminocyclopropane-1-carboxylate N-malonyltransferase(ACC N-MTase) which is responsible for the malonylation of 1-aminocyclopropane-1-carboxylate(ACC) in chickpea (Cicer arietinum) are described. Phosphatebuffer was the most appropriate buffer with regard to enzymestability and, therefore, ACC N-MTase was extracted, assayedand purified in the presence of this buffer. ACC N-MTase waspartially purified approximately 900-fold from embryonic axesof chick-pea seeds using ammonium sulphate precipitation, hydrophobicinteraction and molecular filtration chromatography. By gelfiltration chromatography on Superose-12, the molecular massof the enzyme was estimated to be 54 4 kDa. ACC N-MTase hadan optimal pH and temperature of 7.5 and 40C, respectively,as well as a K_m for ACC and malonyl-CoA of 400 M and 90 M,respectively. D-Phenylalanine was a competitive inhibitor ofACC N-MTase with respect to ACC (K_i of 720 M), whereas co-enzymeA was a competitive product inhibitor with respect to malonyl-CoA(K_i of 300 M) and a non-competitive inhibitor with respectto ACC (K_i of 600 M). Under optimal assay conditions, ACC N-MTasewas strongly inhibited by (a)divalent [Zn²⁺>Mg²⁺>>Co²⁺>Co²⁺>(NH₄)²⁺>Fe²⁺]and monovalent metal cations (Li⁺>Na⁺>K⁺), without activitybeing detected in the presence of Hg²⁺, and (b) PCMB or mersalicacid, suggesting that sulphydryl group(s) are involved at theactive site of the enzyme. Key words: ACC-N-malonyltransferase, Cicer arietinum, embryonic axes, ethylene, germination, seeds     

Prenatal treatment of congenital human cytomegalovirus infection by fetal intravascular administration of ganciclovir

Ganciclovir was administered 'in utero' for 12 days in a 29-week-old fetus with ascertained congenital human cytomegalovirus (HCMV) infection, thrombocytopenia and elevated gamma-glutamyl transferase (gammaGT) value. Efficacy of therapy was shown by reduction in virus titer of amniotic fluid and fetal urine, disappearance of viral DNA in fetal blood, and normalization of platelet count and gammaGT value. However, stillbirth occurred at 32 weeks of gestation and HCMV inclusion bodies were detected in kidneys, lungs, heart and pancreas at autopsy. During therapy, side-effects,possibly related to ganciclovir administration, were observed.     

Partial purification and properties of a 36-kDa 1-aminocyclopropane-1-carboxylate N-malonyltransferase from mung bean

A 36-kDa 1-aminocyclopropane-1-carboxylate (ACC) N-malonyltransferase, which converts the ethylene precursor ACC into the conjugated derivative malonyl-ACC (MACC), has been isolated from etiolated mung bean ( Vigna radiata ) hypocotyls, and partially purified in a four-step procedure. The enzyme is stimulated about 7-fold by 100 m M K⁺ salts or 0.5 m M Co²⁺ salts, and is inhibited competitively by D-phenylalanine (K_i= 1.3 m M ) and non competitively by CoASH (0.3 m M ). Beside malonyl-CoA, it is capable to use succinyl-CoA as an acyl donor. The 36-kDa enzyme described here exhibits a lower optimum temperature (40°C) and a 7- or 3-fold lower apparent K_m for ACC (68 μ M ) and malonyl-CoA (74 μ M ), respectively, when compared with its 55 kDa isoform already isolated from the same plant material. This data support the idea that several isoforms of ACC N-malonyltransferase exist in plants. These isoforms may play a differential role in regulating the availability of ACC, and consequently the rate of ethylene production, as well as detoxifying cells from D-amino acids.     

Desarrollo global del niño: más allá de la suplementación farmacológica con yodo

Iodine deficiency is a factor that may compromise child development, but is not the only one. Other health determinants, some of them outside the healthcare system, are able to influence development. Fighting iodine deficiency may be a pragmatic and useful strategy if it is found to be not maleficent, beneficial to health, and cost-effective, and does not make us lose the notion that child development goes beyond psychomotor or cognitive performance. This article analyzes such constraints from a critical point of view.     

Human talus bones from the Middle Pleistocene site of Sima de los Huesos (Sierra de Atapuerca,Burgos, Spain)

Here we present and describe comparatively 25 talus bones from the Middle Pleistocene site of the Sima de los Huesos (SH) (Sierra de Atapuerca, Burgos, Spain). These tali belong to 14 individuals (11 adult and three immature). Although variation among Middle and Late Pleistocene tali tends to be subtle, this study has identified unique morphological characteristics of the SH tali. They are vertically shorter than those of Late Pleistocene Homo sapiens, and show a shorter head and a broader lateral malleolar facet than all of the samples. Moreover, a few shared characters with Neanderthals are consistent with the hypothesis that the SH population and Neanderthals are sister groups. These shared characters are a broad lateral malleolar facet, a trochlear height intermediate between modern humans and Late Pleistocene H. sapiens, and a short middle calcaneal facet. It has been possible to propose sex assignment for the SH tali based on their size. Stature estimates based on these fossils give a mean stature of 174.4 cm for males and 161.9 cm for females, similar to that obtained based on the long bones from this same site.     

Two strains of Pseudomonas fluorescens bacteria differentially affect survivorship of waxworm (Galleria mellonella) larvae exposed to an arthropod fungal pathogen,Beauveria bassiana

Two strains of Pseudomonas fluorescens were found contaminating a biopesticide used in a previous study against Varroa destructor infestations in honey bee hives. In that study, the biopesticide, a formulation of a fungal pathogen of arthropods, Beauveria bassiana, failed to have any negative impact on the mite infestation despite successful results in previous studies using uncontaminated batches of the same biopesticide. The objective of the present research was to determine whether the bacteria may have interfered with the infectivity and/or virulence of B. bassiana in a simplified system; positive results in that system would then provide a rationale for further work under more complex conditions. Galleria mellonella late instar larvae treated topically with both a bacterial suspension of 6.8 to 7.0×10⁷ cfu/ml and a fungal suspension of 2.5×10⁷ or 2.5×10⁸ B. bassiana conidia/ml showed, in the case of one of the bacterial strains, significantly increased survivorship compared to larvae treated with just the B. bassiana suspension. When larvae were immersed in a bacterial suspension prior to application of B. bassiana suspension using a spray tower, a significant positive effect of the same P. fluorescens strain on larval survivorship was observed at 2.5×10⁸ conidia/ml. Neither the bacterial suspensions alone nor blank control solutions had any effect on larval survivorship. These results show that an interaction between the bacteria and the pathogen may explain some of the results from the prior field trial.     

Toward a Low‐Cost Artificial Leaf: Driving Carbon‐Based and Bifunctional Catalyst Electrodes with Solution‐Processed Perovskite Photovoltaics

Molecular hydrogen can be generated renewably by water splitting with an “artificial‐leaf device”, which essentially comprises two electrocatalyst electrodes immersed in water and powered by photovoltaics. Ideally, this device should operate efficiently and be fabricated with cost‐efficient means using earth‐abundant materials. Here, a lightweight electrocatalyst electrode, comprising large surface‐area NiCo₂O₄ nanorods that are firmly anchored onto a carbon–paper current collector via a dense network of nitrogen‐doped carbon nanotubes is presented. This electrocatalyst electrode is bifunctional in that it can efficiently operate as both anode and cathode in the same alkaline solution, as quantified by a delivered current density of 10 mA cm^?2 at an overpotential of 400 mV for each of the oxygen and hydrogen evolution reactions. By driving two such identical electrodes with a solution‐processed thin‐film perovskite photovoltaic assembly, a wired artificial‐leaf device is obtained that features a Faradaic H₂ evolution efficiency of 100%, and a solar‐to‐hydrogen conversion efficiency of 6.2%. A detailed cost analysis is presented, which implies that the material‐payback time of this device is of the order of 100 days.