Isolation and characterisation of genes for sulphate activation and reduction in Aspergillus nidulans: implications for evolution of an allosteric control region by gene duplication

A region of the Aspergillus nidulans genome carrying the sA and sC genes, encoding PAPS reductase and ATP sulphurylase, respectively, was isolated by transformation of an sA mutant with a cosmid library. The genes were subcloned and their functions confirmed by retransformation and complementation of A. nidulans strains carrying sA and sC mutations. The physical distance of 2 kb between the genes corresponds to a genetic distance of 1 cM. While the deduced amino acid sequence of the sA gene product shows homology with the equivalent MET16 gene product of Saccharomyces cerevisiae, the sC gene product resembles the equivalent MET3 yeast gene product at the N-terminal end, but differs markedly from it at the C-terminal end, showing homology to the APS kinases of several microorganisms. It is proposed that this C-terminal region does not encode a functional APS kinase, but is responsible for allosteric regulation by PAPS of the sulphate assimilation pathway in A. nidulans, and that the ATP sulphurylase encoding-gene (sC) of filamentous ascomycetes may have evolved from a bifunctional gene similar to the nodQ gene of Rhizobium meliloti.     

Micropropagation of Stryphnodendron polyphythum (Barbatimão)

Stryphnodendron polyphythum Mart., popularly known as Barbatimão, is a native Brazilian tree widely used in folk medicine as a wound healing agent. Cotyledonary node segments were placed on Murashige and Skoog (MS) medium supplemented with different types and concentrations of cytokinins. The medium that gave best shoot proliferation contained 13.3 M 6-benzyladenine (BA). However, MS supplemented with 0.04 M BA and 0.005 M indole-3-acetic-acid enhanced shoot length. Root formation was best on shoots inserted into medium with half-strength macronutrients supplemented with 5.37 M naphthaleneacetic acid and 80 mg 1^–1 phloroglucinol.     

Fructose mono- and polycaprylate purification by molecular distillation

A mixture of free caprylic acid and fructose caprylates obtained by biocatalysis was separated by molecular distillation (short path distillation). The optimum temperature and pressure (60°C and 0.1 bar) take account of the heat-sensitivity of these compounds.     

Antibiotic activity of new cyanobacterial isolates from Australia and Asia against green algae and cyanobacteria

One hundred and ninety-eight cyanobacterial strains, newly isolated mainly from samples collected from diverse habitats in Australia, Indonesia, Nepal, Thailand and Vietnam, were screened from their antibiotic activity against green algal species of the genera Coelastrum, Scenedesmus and Monoraphidium. We report the discovery of ten strains of Fischerella, seven of Nostoc and three of Calothrix that produce antialgal compounds with a broad activity spectrum. Some of these bioactive cyanobacteria inhibited all three algae, whereas others inhibited only two, and some only one. In addition, the 20 active strains were tested against other selected cyanobacteria, including Anabaena doliolum which grows well both photoautotrophically in light and heterotrophically in darkness, and three toxic species, Microcytis aeruginosa, Anabaena circinalis and Nodularia spumigena, which are problems in Australia and other parts of the world. At least one Fischerella strain had bioactivity directed against photosynthetic electron transport of algal chloroplasts, whereas others had no effect on photosynthesis. In most cases the growth inhibitory effects were also tested in the presence of a proteinase. The results are discussed in the light of the possible nature of the chemical inhibition and also in relationship to competition and allelopathy in algal populations. This revised version was published online in June 2006 with corrections to the Cover Date.     

Zinc sulfate supplementation improves thyroid function in hypozincemic down children

In subjects affected by trisomy 21 (Down syndrome), hypothyroidism is the most common endocrinological deficit. Plasma zinc levels, which are commonly detected below the normal range in Down patients, are related to some endocrinological and immunological functions; in fact, zinc deficiency has been shown to impair immune response and growth rate. Aims of this study were to evaluate (1) the role of zinc deficiency in subclinical hypothyroidism and (2) thyroid function changes in Down children cyclically supplemented with zinc sulfate. Inverse correlations have been observed between age and triiodotironine (T3) and between zinc and thyroid-stimulating hormone (TSH); higher TSH levels have been found in hypozincemic patients at the beginning of the study. After 6 mo of supplementation, an improvement of thyroid function (TSH levels: 3.96 ± 1.84 vs 2.64 ± 1.33 mUI/mL basally and after 6 mo, respectively) was observed in hypozincemic patients. In the second cycle of supplementation, a similar trend of TSH was observed. At the end of the study, TSH significantly decreased in treated hypozincemic subjects (4.48 ± 1.93 vs 2.96 ± 1.20 mUI/mL) and it was no longer different in comparison to normozincemic patients. We suggest zinc supplementation to the diet in hypozincemic Down children as a simple and useful therapeutic tool.     

Mitochondrial respiration in muscle and liver from cold-acclimated hypothyroid rats.

The effects of long-term cold exposure on muscle and liver mitochondrial oxygen consumption in hypothyroid and normal rats were examined. Thyroid ablation was performed after 8-wk acclimation to 4 degrees C. Hypothyroid and normal controls remained in the cold for an additional 8 wk. At the end of 16-wk cold exposure, all hypothyroid rats were alive and normothermic and had normal body weight. At ambient temperature (24 degrees C), thyroid ablation induced a 65% fall in muscle mitochondrial oxygen consumption, which was reversed by thyroxine but not by norepinephrine administration. After cold acclimation was reached, suppression of thyroid function reduced muscle mitochondrial respiration by 30%, but the hypothyroid values remained about threefold higher than those in hypothyroid muscle in the warm. Blockade of beta- and alpha1-adrenergic receptors in both hypothyroid and normal rats produced hypothermia in vivo and a fall in muscle, liver, and brown adipose tissue mitochondria respiration in vitro. In normal rats, cold acclimation enhanced muscle respiration by 35%, in liver 18%, and in brown adipose tissue 450% over values in the warm. The results demonstrate that thyroid hormones, in the presence of norepinephrine, are major determinants of thermogenic activity in muscle and liver of cold-acclimated rats. After thyroid ablation, cold-induced nonshivering thermogenesis replaced 3,5,3'-triiodothyronine-induced thermogenesis, and normal body temperature was maintained.     

Pollen ontogenesis in Oenothera: a comparison of genotypically normal anthers with the male-sterile mutant sterilis

Summary A 12-stage normal table of anther development in Oenothera, is presented. The stages are characterized by developmental steps in the reproductive cells and the tapetum, including waves of amylogenesis and lipogenesis as well as the production of the sporoderm layers. This is compared to a corresponding table for the male-sterile (mst) mutant sterilis (ster). Differences between the development of fertile and mst anthers appear after the liberation of the microspores from the tetrads. Male sterility results from a malfunction of the tapetum in the production of ektexine sporopollenin precursors, which aggregate in the tapetal cells. The consequence is the absence of ektexine from the microspores. The endexine is then dissolved, presumably by an enzyme. This process leads to naked microspores whose unprotected cytoplasms are attacked by hydrolytic enzymes present in the thecal fluid. At anthesis the anthers contain only undefined remnants of microspores and tapetum.     

A genomic island of the sulfate-reducing bacterium Desulfovibrio vulgaris Hildenborough promotes survival under stress conditions while decreasing the efficiency of anaerobic growth

A 47 kb genomic island (GEI) bracketed by 50 bp direct repeats, containing 52 annotated genes, was found to delete spontaneously from the genome of Desulfovibrio vulgaris Hildenborough. The island contains genes for site-specific recombinases and transposases, rubredoxin:oxygen oxidoreductase-1 (Roo1) and hybrid cluster protein-1 (Hcp1), which promote survival in air and nitrite stress. The numbering distinguishes these from the Roo2 and Hcp2 homologues for which the genes are located elsewhere in the genome. Cells with and without the island (GEI⁺ and GEI^- cells respectively) were obtained by colony purification. GEI^- cells arise in anaerobic cultures of colony-purified GEI⁺ cells, indicating that the site-specific recombinases encoded by the island actively delete this region. GEI⁺ cells survive better in microaerophilic conditions due to the presence of Roo1, whereas the Hcps appear to prevent inhibition by sulfur and polysulfide, which are formed by chemical reaction of sulfide and nitrite. Hence, the island confers resistance to oxygen and nitrite stress. However, GEI^- cells have a higher growth rate in anaerobic media. Microarrays and enzyme activity stains indicated that the GEI^- cells have increased expression of genes, which promote anaerobic energy conservation, explaining the higher growth rate. Hence, while lowering the efficiency of anaerobic metabolism, the GEI increases the fitness of D. vulgaris under stress conditions, a feature reminiscent of pathogenicity islands which allow more effective colonization of environments provided by the targeted hosts.     

Reduced ligand affinity leads to an impaired function of the adenosine A2A receptor of human granulocytes in sepsis

The enhanced release of reactive oxygen species by excessively activated polymorphonuclear leucocytes (PMN) is a key step in the pathogenesis of sepsis. Potent action of adenosine in inhibiting cytotoxic PMN functions has been documented. Recent data, however provide evidence that in sepsis a diminished capability of adenosine to inhibit the generation of oxygen radicals by PMN occurs. Here, we investigated the underlying mechanisms in an in vitro sepsis model and in PMN of sepsis patients. We report that lipopolysaccharide (LPS)-incubation of human PMN elicited the same increase in the half-maximal inhibitory concentration (IC₅₀) of adenosine as observed in patients with septic shock. Coupling to adenylyl cyclase was impaired as well, as indicated by a decreased potency of adenosine to stimulate cyclic adenosine monophosphate (cAMP) accumulation. Ligand-binding studies conducted with native, LPS-stimulated PMN, and with PMN of sepsis patients revealed that, despite an increased adenosine A_2A receptor (A_2AR) expression, the receptor function declines due to a diminished ligand-binding affinity most likely caused by allosteric modulators within the inflammatory environment. A_2AR function obviously is highly dependent upon the cellular environment and thus, further functional characterization of A_2AR responses in sepsis may be a promising approach to develop new adenosine or A_2AR agonists based therapeutic strategies.