Rheology of hydroxyethyl guar gum derivatives

The rheological properties of aqueous solutions of hydroxyethyl guar gum, a synthetic derivative of guar gum, have been studied under continuous and oscillatory shear flow conditions. Data obtained from both experimental techniques were satisfactorily fitted according to Cross-type models. The effect of polymer concentration, molecular weight and temperature on the rheological behavior of hydroxyethyl guar gum systems have been investigated and discussed in terms of rheological parameters like the zero-shear viscosity η₀ and the characteristic times λ and λ′.     

Muscle differentiation in a colonial ascidian: organisation, gene expression and evolutionary considerations

Background  

Ascidians are tunicates, the taxon recently proposed as sister group to the vertebrates. They possess a chordate-like swimming larva, which metamorphoses into a sessile adult. Several ascidian species form colonies of clonal individuals by asexual reproduction. During their life cycle, ascidians present three muscle types: striated in larval tail, striated in the heart, and unstriated in the adult body-wall.     

A carbapenem-resistant Klebsiella pneumoniae isolate harboring KPC-1 from Italy

Carbapenem-resistant gram-negative pathogens represent an emerging threat to the management of hospital-acquired infections. Although the isolation of carbapenem-resistant enterobacteriaceae remains unusual, the frequency of carbapenemases producing Klebsiella pneumoniae is increasing in different geographic regions: the majority of isolates has been collected in the USA, but recently KPC-producing K. pneumoniae were reported from China, Israel, Greece, France, Norway and Sweden. We report a KPC 1-producing K. pneumoniae isolate from Italy. This datum enlarges the geographical area where the KPC-producing K. pneumoniae strains are diffuse.     

Genetic mapping and QTL analysis in European hazelnut (<Emphasis Type="Italic">Corylus avellana</Emphasis> L.)

The European hazelnut (Corylus avellana L.) is the most economically important nut species in the Betulaceae family. Despite the need for new improved hazelnut cultivars, few breeding programs are carried out because of the large plant size, the long lifecycle of the plant, and the expense and time required. To date, there are no reports of maps with quantitative trait loci (QTL) in hazelnut. Our objective in the present study was to identify QTL associated with vegetative traits to allow marker-assisted selection (MAS). An F1 progeny (275 plants) of Tonda Gentile delle Langhe × Merveille de Bollwiller obtained in 2009 was used to develop a QTL linkage map for vigour, sucker habit, and time of bud burst, after three years of observations. A set of 163 plants were analysed with 152 microsatellite markers. A map of 11 linkage groups was obtained, covering 663.1 cM, and 15 QTLs were identified and mapped for the traits examined. Of them, 10 were ‘major’ QTL, including a stably expressed region on LG_02 for leaf bud burst. At least one major QTL for each year underlies the variation in each trait and a clustering of QTL for trunk circumference and suckers/trunk circumference ratio with high inter-trait correlations was observed on LG_05, suggesting a single pleiotropic locus. This research represents an initial step in the future identification of chromosomal regions carrying genes of interest, important for breeding programs and MAS.     

Two forms of NADP-dependent malic enzyme in expanding maize leaves

Etiolated maize leaves (Zea mays L.) contain a major isozyme of NADP-dependent malic enzyme (L-malate dehydrogenase, decarboxylating, EC 1.1.1.40) having an isoelectric point of 5.28±0.03, a K_m (L-malate) 0.3–0.6 mM at pH 7.45; a broad pH optimum around pH 6.9 under the conditions of assay; a molecular weight of 280,000 (sometimes accompanied by a minor component of 150,000); and an NAD-dependent activity about 1/50 the NADP-dependent activity. This isozyme, resembling the NADP-malic enzyme of vertebrates, is labeled type 1. The dominant isozyme of young green leaves (type 2) has, however, a pI 4.90±0.03, a K_m (L-malate) 0.10–0.15 mM, a pH optimum of 8, and a molecular weight of 280,000. It is also more stable and exhibits an appreciable NAD-dependent activity (1/5–1/7 the NADP activity). Both isozymes show linear kinetics, dependence on Mn or Mg ions, similar K_m (NADP⁺), and the typical increase of K_m for L-malate with increasing pH values. Type 1 isozyme of maize is assumed to be cytosolic. Type 2 corresponds in each property to the chloroplast enzyme of bundle-sheath cells. It is present at a low level in etiolated leaves and develops to a high specific activity (up to 100 nmol min^-1 mg protein^-1 by 150 h illumination) during photosynthetic differentiation, replacing the type 1 form.Abbreviation MES 2 (N-morpholino)ethane sulfonic acid Work supported by grants from the Consiglio Nazionale delle Ricerche for years 1975 and 1976