Activation of phospholipase A2 by freshly added lysophospholipids

Reaction progress curves for the hydrolysis of dimyristoylphosphatidylcholine by pig pancreatic phospholipase A₂ exhibits a latency phase. Addition of 1-palmitoyllysophosphatidylcholine to the preformed vesicles reduces the latency phase and enhances the binding of phospholipase A₂ to the vesicles. In contrast, the binary codispersions prepared from diacylphospholipids premixed with lysophosphatidylcholine do not exhibit such enhanced susceptibility to the phospholipase. This effect appears to be due to organizational defects created by asymmetrical incorporation of lysophospholipid molecules into the outer monolayer of the vesicles, and the action of phospholipase is not observed when the additive is equilibrated in both the monolayers of the vesicles.     

Oligomerization-mediated activation of plasmid-borne genes in Escherichia coli

A plasmid carrying a weakly expressed neomycin phosphotransferase (neo) gene from the transposable element Tn5 was found to confer elevated levels of antibiotic resistance on its host cell when it existed in a non-monomeric state. This activation of the neo gene appeared to be a generalized effect which can be exerted on any plasmid-encoded gene, since specific sequences were not required for enhanced neo expression, and the activity of a plasmid-borne chloramphenicol acetyltransferase gene could be similarly induced by oligomerization. The potential role that multiple origins of replication present in such oligomeric plasmids play in these observed increases in gene expression is discussed.     

Eveningness and poor sleep quality contribute to depressive residual symptoms and behavioral inhibition in patients with bipolar disorder

ABSTRACT

Eveningness and sleep disturbances are considered as markers of Bipolar Disorder (BD) and influence mood and emotional or behavioral states. This study investigates the associations between circadian markers and sleep quality on residual depressive symptoms and inhibition/activation dimensions during the euthymic phase. A sample of 89 euthymic adult individuals with BD was assessed for circadian preference and typology using the Composite Scale of Morningness (CSM) and the Circadian Type Inventory (CTI) and for sleep quality using the Pittsburgh Sleep Quality Index (PSQI). The Montgomery and Asberg Depression Rating Scale (MADRS) and the Multidimensional Assessment of Thymic States (MAThyS) were used to measure residual depressive symptoms and the inhibition/activation dimensions. We examined any associations between these parameters using correlations and path analyses. We identified significant associations between eveningness and poorer sleep quality that correlated to higher depressive residual symptoms and a global inhibition. The use of path analyses led us to conclude that poor sleep quality mediated the relationship between eveningness and either residual mood symptoms or behavioral inhibition (motivation, sensory perception, interpersonal interaction, and cognition). These factors should be considered in the clinical evaluation of individuals with BD, with a specific attention during the euthymic phase, in order to achieve the best functional outcome possible.     

Review the formation of adventitious roots: New concepts, new possibilities

Summary Considerable progress has recently been made in understanding adventitious root formation using physiological studies. It is recognized that rooting is a process consisting of distinct phases, each with its own requirements. In this review, the successive phases in the rooting process are described and the possible roles of wounding-related compounds, auxin, ethylene and phenolic compounds during these specific phases are discussed. Recent results are assisting the development of advanced rooting treatments. Molecular studies on rooting are underway and will be essential in revealing the mechanisms underlying adventitious root formation.     

Reduction of ferredoxin:thioredoxin reductase by artificial electron donors

The ferredoxin:thioredoxin reductase is an essential enzyme of the light dependent regulatory system in oxygenic photosynthesis. It is composed of two dissimilar subunits and contains a 4Fe-4S cluster and a redox-active disulfide bridge. Artificial electron donors of redox potentials below –300 mV are capable of reducing the disulfide bridge. Based on our results we speculate that a group of more negative potential than the disulfide bridge is the first acceptor of the electrons in FTR. The chemical reduction of FTR has been used successfully for the detection of the enzyme during its purification.Abbreviation FBPase fructose 1,6-bisphosphatase - FTR ferredoxin:thioredoxin reductase - MV methyl viologen Dedicated to Prof. D.I. Arnon.     

Structural and trace element changes in scalp hair of radiographers

Scalp hair samples were collected from medical radiographers and nonradiographers of matching age groups. Structural morphology of hair was studied by scanning electron microscopy, and the trace element profiles in hair were measured using neutron activation analysis. The structural damage to the hair follicles of the radiographers was quite obvious, and this may be a good qualitative indicator of radiation damage at low doses. The concentrations of aluminum (Al), potassium (K), and vanadium (V) in hair of the radiographers were significantly higher, whereas those of antimony (Sb) and magnesium (Mg) were significantly lower than those of nonradiographers. Some of our findings were quite consistent with those of others in determining the changes in trace element concentrations in irradiated tissue.     

Production of α-keto acids: 2. Immobilized whole cells of Providencia sp. PCM 1298 containing -amino acid oxidase

A number of bacteria belonging to the genera Proteus, Providencia, Pseudomonas and Erwinia have been tested for their capacity to oxidize -amino acids to their corresponding α-keto acids. Members of the Proteus and the Providencia genera were active towards various -amino acids. Immobilized cell preparations of Providencia sp. PCM 1298 were shown to form up to 80 mg α-keto-γ-methiol butyric acid from -methionine per g of gel preparation (containing 4% w/w cells) per day. The productivity was highly dependent on the size of the beads. Oxygen appeared to be the rate-limiting substrate and oxygen transfer rates of 3–4 μmol cm⁻² h⁻¹ were calculated. The entrapment of activated charcoal to remove H₂O₂ formed during the oxidation extended the half-life of the immobilized biocatalyst considerably. A decrease in -amino acid oxidase [ -amino acid: oxygen oxidoreductase (deaminating); EC 1.4.3.2] activity during operation could be compensated for by reinoculation of the alginate-entrapped cells in fresh growth medium, allowing use of these preparations of immobilized bacterial cells for more than one month.     

Temperature dependence of membrane permeability in cultured cells exposed to benzene and phenol

The effects of benzene (20mM) and phenol (20mM) on the passive membrane permeability of cultured cells of neuronal (N1E115), glial (138MG), muscle (L6) and liver (BRL123) origin were studied. Permeability changes were assayed as alterations in the release of radioactivity from cells preloaded with [³H]2-deoxy-D-glucose. Temperature plots of the efflux revealed that benzene and phenol caused altered flux rates in N1E115 cells without affecting the activation energy. Also in 138 MG cells the activation energy was unaffected by both compounds, while phenol decreased the flux rates. Benzene had no effect on the efflux in L6 cultures, whereas a low activation energy efflux was induced by phenol. In BRL123 cells both benzene and phenol induced a dual (high and low) activation energy efflux.     

Studies on zymogenicity and solubilization of chitin synthase from Candida albicans

Abstract The zymogenic form of the chitin synthase present in mixed membrane preparations was extracted by digitonin treatment. The residual extracted membranes exclusively retained the basal activity. Trypsin activation of the zymogenic form of the enzyme did not modify the digitonin solubilization characteristics of the original zymogenic form, suggesting significant differences between 'in vivo' activation of chitin synthase and that carried out by trypsin 'in vitro'.