Effect of noradrenaline chronic administration on brown fat phospholipids

Chronic cold exposure of rats (9 days at 5°C) induces an alteration of the fatty acid composition of phospholipids in brown adipose tissue. The alteration is due to an increase of the unsaturation degree of these lipids. The phenomenon can be reproduced by 10^–7 mole. h^–1 administration of noradrenaline for 9 days in rats kept at 25°C. Thus, phospholipid alteration in brown fat of cold exposed rats is most probably a consequence of the increase of sympathetic tone which occurs in this tissue during exposure to cold.     

Characterization of the cellulase complex from Cellulomonas grown on bagasse pith

Summary The effect of physico-chemical parameters on the cellulolytic activity of Cellulomonas sp. IIbc grown on sugarcane bagasse pith was investigated, and the optimum ranges for enzyme activity were established. The cellulases were more stable when incubated at the optimum growth temperature (32°C) than under optimum activity conditions (45°C for -glucosidases and 50°C for CMC- and FP-cellulases). The -glucosidases were the thermostability-limiting enzymes of the complex. Two types of endoglucanases could be recognized according to their adsorption properties on bagasse: one weakly-bound and one tightly-bound type, the latter constituting approximately 73% of the extracellular endoglucanases at exponential growth phase. Four forms active on filter paper and three active on CMC were obtained by HPLC separation of the extracellular fraction of the culture at stationary phase.Abbreviations CMC carboxymethylcellulose - FP filter paper     

In vitro propagation of mature trees of Alnus incana (L.) Moench.

Mature trees of European grey alder (Alnus incana) were micropropagated on a modified MS medium containing 2.5 M BA, 6.2 mM (500 mg l^-1) NH₄NO₃ and 1.5% glucose. Prior to in vitro culture, mature scions were multiplied through grafting and cutting techniques. Shoot tips from cuttings were established in vitro. After six months of culture, shoots were rooted either in vitro or in vivo and plantlets were transferred to greenhouse conditions.     

Saint Lucia revisited

The eastern Caribbean island of Saint Lucia is now famous in parasitological history as the setting for a major programme of schistosomiasis control'. Perhaps less well-known are the island's effective control of many intestinal parasites, and elimination of malaria, such that the current patterns of mortality and other demographic indicators now resemble those of industrialized countries. More recently, the island has become the focus for another community-based health programme as the Caribbean region again comes to grips with Aedes aegypti and its recently imported relative, Aedes albopictus, important vectors of yellow fever and dengue viruses (see Box 1).     

Vitamin A excess alters membrane flow in rat liver

Pulse-chase methodology with [35S]methionine as label was employed to determine flow kinetics through the endoplasmic reticulum-Golgi apparatus-(lysosome-) secretory vesicle-plasma membrane export route in livers of animals receiving vitamin A excess by gavage. Overall fraction composition determined by morphometry and by analyses of marker enzymes was unchanged by vitamin administration. The vitamin modified the pattern of flow of proteins through the Golgi apparatus to the cell surface and to lysosomes. Altered flux was evidenced by a markedly reduced rate of labeling of lysosomes and a slightly increased rate of labeling of both total membrane proteins of the plasma membrane and of a specific membrane glycoprotein GP80. Also reduced was overall labeling of the Golgi apparatus. Differences in the rate or routes of trafficking of glycoproteins through the Golgi apparatus together with altered opportunities for processing might account for some of the alterations in glycoconjugate glycosylation associated with excess vitamin A administration.     

Space-variant visual processing: spatially limited visual channels

A multichannel model incorporating visual inhomogeneity is presented in this paper. The parameters that describe inhomogeneity have been experimentally obtained both at threshold and in several suprathreshold conditions. At threshold, probability summation is taken into account in order to determine the spatial extent of visual channels from experimental data showing an asymptotic increase in sensitivity with increasing grating area. At suprathreshold contrast, the region where luminance variations at several scales are visible has also been found. The results support a spatially limited multichannel model of early visual processing and set out a basis for studying perceptual phenomena from the viewpoint of linear space-variant visual processing.     

Effect of adaptation to high light intensity on the kinetics of energy transfer from phycobilisomes to photosystem II in Anabaena cylindrica

Transfer efficiencies between phycobilisomes and photosystem II antenna chlorophylls were determined on membrane fragments isolated from low and high light adapted Anabaena cells. The observed increase in energy transfer in high light adapted cells is a consequence of shorter interchromophore distances and a decrease in the number of jumps of the exciting photons. Calculation of the rates of energy transfer and the coupling energies indicate that the weak interaction inferred for energy transfer between phycobilisome and photosystem II in low light adapted cells is replaced by an intermediate interaction in high light adapted cells.Abbreviations LLA low light adapted - HLA high light adapted - PBS phycobilisome - PS photosystem     

Physiological control and process kinetics of clavine alkaloid production byClaviceps purpurea

Summary Kinetic parameters of production of clavine alkaloids were evaluated in twoClaviceps purpurea strains. Mutagenesis brought about enhanced resistance of the biosynthetic system towards alkaloids. Addition of glucose into the fermentation medium altered the zero order kinetics of production to activation-inhibition kinetics. The glucose treatment allowed performance of both elymoclavine-inhibitionless and clavine alkaloid-decompositionless fermentations if a combination of fermentation and separation units in a closed loop was used.Nomenlacture k ₁ rate constant of agroclavine synthesis (mg Agro · mg Elymo/l·g DW·day for stage 1, mg Agro/g DW·day for stage 2) - k ₂ parameter describing inhibition of agroclavine formation rate by elymoclavine (mg Elymo/l) - k ₃ specific rate of agroclavine decay (l/g DW·day) - k ₄ maximal specific rate of elymoclavine synthesis (stage 1, 1/g DW·day, stage 2, mg Elymo/g DW·day) - k ₄ ^– maximal specific rate of elymoclavine synthesis in stage 1 (inhibition-activation mechanism) (mg Elymo/g DW·day) - k ₅ physiological constant describing the elymoclavine decay rate (l²/g DW·day·mg Elymo) - k ₅ ^– physiological constant describing the activation of elymoclavine biosynthesis by elymoclavine (mg Elymo/l) - k ₆ physiological constant describing the repression of elymoclavine biosynthesis by elymoclavine (mg Elymo/l) - k ₇ maximal specific growth rate (1/day) - k ₈ specific rate of biomass decay (l/g DW·day) - A agroclavine concentration (mg/l) - E elymoclavine concentration (mg/l) - r _A specific rate of agroclavine biosynthesis (mg Agro/g DW·day) - r _E specific rate of elymoclavine biosynthesis (mg Elymo/g DW·day) - r _i specific rate of alkaloid biosynthesis (mg alkaloid/g DW·day) - X dry biomass concentration (g/l) - specific growth rate (1/day) Abbreviations Agro agroclavine - Elymo elymoclavine - Chano chanoclavine - DW dry weight of biomass     

Citrate utilization by free and immobilized Streptococcus lactis subsp. diacetylactis in continuous culture

Summary The effects of pH, temperature and concentration of citrate were investigated to achieve an optimal production of diacetyl, acetoin and C₂ compounds such as acetaldehyde, acetate and ethanol for free and immobilized cells. The critical conditions of culture, 22°C, pH 4.8, increased the production of C₄ compounds (diacetyl, acetoin, 2, 3 butylene glycol), C₂ compounds (acetaldehyde, ethanol, acetate) and formate. A higher yield of C₂ and C₄ compounds was observed for the immobilized cells than for the free cells in continuous culture. At 75 mMol/l of citrate, the citrate bioconversion yield was 42.8% and 80% for free and immobilized cells, respectively. This paper discusses citrate and lactose utilization and NADH₂ part on diacetyl reduction.