Isolation and Purification of Enzymes from Ligninolytic Complex of the Basidial Fungus <Emphasis Type="Italic">Trametes pubescens</Emphasis> (Schumach.) Pilat and Study of Their Properties

A method for purification of enzymes from the ligninolityc complex of the basidiomycete Trametes pubescens (Schumach.) Pilat has been elaborated. Two homogeneous isoforms of laccases (laccase 1 and laccase 2) as well as a homogeneous preparation of lignin peroxidase were isolated. Basic biochemical parameters of the enzymes were determined, such as the molecular weights (67, 67, and 45 kD, respectively), isoelectric points (5.3, 5.1, and 4.2, respectively), as well as content and composition of the carbohydrate moiety of the laccases (N-acetylglucosamine, mannose, and xylose). The pH dependences and thermal stabilities of the laccases were investigated. The kinetic parameters of the enzymatic reactions catalyzed by the laccases were determined using different substrates, such as catechol, hydroquinone, 2,2 -azinobis-(3-ethylbenzthiazoline-6-sulfonate), and K4Fe(CN)6. The structure of the active sites of both laccases and the lignin peroxidase were studied by EPR, CD, and UV-VIS spectroscopy, as well as using fluorescence analysis. Our studies showed similarity of the spectral characteristics of the two laccases, whereas their kinetic properties were found to be different.     

Cell—cell interactions in bacterial populations

In developing bacterial populations many essential processes, such as division, genetic transformation, sporulation, and synthesis of antibiotics and secondary metabolites, are regulated by intercellular communication mediated by secretion of signaling molecules, such as homoserine lactones and peptides. Another intercellular communication type, namely a physical contact between cells (cell aggregation), plays a key role in formation of biofilms or cellular consortia and in cell proliferation under unfavorable conditions. The mechanisms involved in these two types of bacterial communication are discussed in this review.Translated from Biokhimiya, Vol. 69, No. 11, 2004, pp. 1555–1564.Original Russian Text Copyright © 2004 by Voloshin, Kaprelyants     

A new alkalitolerant <Emphasis Type="Italic">Yarrowia lipolytica</Emphasis> yeast strain is a promising model for dissecting properties and regulation of Na<Superscript>+</Superscript>-dependent phosphate transport systems

A newly isolated osmo-, salt-, and alkalitolerant Yarrowia lipolytica yeast strain is distinguished from other yeast species by its capacity to grow vigorously at alkaline pH values (9.7), which makes it a promising model organism for studying Na⁺-dependent phosphate transport systems in yeasts. Phosphate uptake by Y. lipolytica cells grown at pH 9.7 was mediated by several kinetically discrete Na⁺-dependent systems specifically activated by Na⁺. One of these, a low-affinity transporter, operated at high concentrations of extracellular phosphate. The other two, high-affinity systems, maximally active in phosphate-starved cells, were repressed or derepressed depending on the prevailing extracellular phosphate concentration and pH value. The contribution of Na⁺/P_i-cotransport systems to the total cellular phosphate uptake progressively increased with increasing pH, reaching its maximum at pH 9.Translated from Biokhimiya, Vol. 69, No. 11, 2004, pp. 1607–1615.Original Russian Text Copyright © 2004 by Zvyagilskaya, Persson.     

Role of inhibitors of proteolytic enzymes in plant defense against phytopathogenic microorganisms

This review analyzes the literature on various mechanisms of proteolytic enzyme inhibitors involved in plant defense against attack by phytopathogenic microorganisms. The action of proteinase inhibitors from plants upon the enzymes from pathogenic microorganisms and viruses is reviewed. Considerable attention is given to the induction of proteinase inhibitors in plants in response to the invasion of pathogens. Some aspects of application of proteinase inhibitors in biotechnology for production of transgenic plants with enhanced resistance to diseases are discussed.Translated from Biokhimiya, Vol. 69, No. 11, 2004, pp. 1600–1606.Original Russian Text Copyright © 2004 by Valueva, Mosolov.     

Adiposity and eating behaviors in patients under second generation antipsychotics

Background: Second generation antipsychotics (SGA) induce substantial weight gain but the mechanisms responsible for this phenomenon remain speculative. Objective: To explore eating behaviors among SGA‐treated patients and compare them with nonschizophrenic healthy sedentary individuals (controls). Methods and Procedures: Appetite sensations were recorded before and after a standardized breakfast using visual analog scales. Three hours after breakfast, a buffet‐type meal was offered to participants to document spontaneous food intake and food preferences. Satiety quotients (SQs) were calculated to determine the satiation of both meals and the Three‐Factor Eating Questionnaire (TFEQ) was used to document eating behaviors. Body composition and abdominal fat distribution were assessed. Results: Compared with controls (n = 20), SGA‐treated patients (n = 18) showed greater adiposity indices (P ≤ 0.04). Patients' degree of hunger was also higher following the standardized breakfast (P = 0.03). Moreover, patients had significantly higher cognitive dietary restraint, disinhibition, and susceptibility to hunger scores than the reference group (P ≤ 0.05). Disinhibition in the reference group was positively associated with hunger triggered by external cues (r = 0.48, P = 0.03) whereas internal cues seem to mainly regulate emotional susceptibility to disinhibition in patients (r = 0.56, P = 0.02). Higher strategic restraint behavior in patients was associated with decreased satiation right after the buffet‐type meal (r = ?0.56, P = 0.02). Discussion: These exploratory findings suggest that patients under SGA seem to develop disordered eating behaviors in response to altered appetite sensations and increased susceptibility to hunger, a factor which may influence the extent of body weight gain triggered by these drugs.     

Temporal and spatial patterns of crustacean zooplankton dynamics in a transitional lagoon ecosystem

Patterns and mechanisms of plankton crustacean seasonal succession in the eutrophic freshwater Curonian lagoon (south-eastern Baltic Sea) were analysed on the basis of four-year (1995, 1996, 1998 and 1999) field sampling results. The seasonal crustacean zooplankton succession in the lagoon appears to be the consistent six-stage sequence of four distinct species complexes. Each stage is characterised by its individual species composition and quantitative characteristics. The uniform and periodic pattern of the limnetic zooplankton crustacean successional stages in the lagoon indicates that the seasonal succession of the limnetic zooplankton is not disturbed by unpredictable environmental fluctuations, such as brackish water inflows. Seasonal zooplankton succession is also comparatively uniform at a spatial scale. Not more than two adjacent successional stages were found across the northern part of the lagoon during each of 11 seasonal surveys. Comparison between monthly water residence time and dominant plankton crustacean species life cycle duration points to a more transitory plankton community in spring while in the summer it is not much influenced by lagoon hydrodynamics. Consequently, the Curonian lagoon crustacean community quite closely follows the Plankton Ecology Group (PEG)-described freshwater lake seasonal succession in summer and turns into a lentic-like system in spring and autumn.     

Bending of apricot tree branches under the weight of axillary growth: test of a mechanical model with experimental data

Stem orientation is an important factor for fruit tree growth and branching habit since it influences fruit production as well as training practices. A mechanical model of the bending of a stem under axillary load was written and evaluated using experimental data on apricot trees (Prunus armeniaca L.). A set of 15 1-year-old stems of various shapes was observed during the early stage of the growing season when radial growth is still negligible and the loading of the stem increases considerably. The structural modulus of elasticity (MOE) of the stems was estimated through in situ bending tests assuming homogeneous material behaviour. The effect of viscoelasticity was observed through creep tests performed on similar stems during winter. Inputs of the model are initial shape, initial diameter, and final load, defined at various positions along the stem. The final shape was simulated based on different mechanical assumptions, and compared to observations. Assuming small deflections resulted in an underestimate of the mean slope variation of 48%, accounting for large displacements reduced this underestimate to 29% and accounting for viscoelasticity reduced it further to 14%. An adjustment of the structural MOE to fit the final shape led to an excellent fit of the data in most cases, the residual errors for some axes being attributed to material heterogeneity. The use of biomechanical models to predict the shape of fruit trees based on growth parameters, provided adequate assumptions are made, is discussed.     

Regional and gender variations in adipose tissue lipolysis in response to weight loss.

Catecholamine-induced lipolysis was investigated in 32 obese subjects (14 men and 18 premenopausal women), aged 36-50 years, whose body mass index ranged from 30 to 42 kg/m(2). Isolated subcutaneous (subc) abdominal and femoral adipocytes were studied before and after a 15-week weight reducing program, during which mean body weight loss averaged 9 vs. 10 kg in women and men, respectively (P < 0.0001). Participants were re-examined when they were weight-stable. Fat cell weight decreased by about 15;-20% in both depots (P values ranging from 0.01 to 0.05). Epinephrine (mixed alpha2-/beta-adrenoceptor (AR) agonist) induced antilipolysis at low concentrations and a net lipolytic response at higher doses, irrespective of subjects' fatness and anatomic location of fat. Basal lipolysis, maximal lipolytic responses to isoprenaline (beta-AR agonist), dobutamine and procaterol (beta1- and beta2-AR agonists, respectively) as well as maximal antilipolytic effects of epinephrine or UK-14304 (alpha2-AR agonist) were similar before and after weight reduction. However, both beta- and beta2-AR lipolytic sensitivities and the beta-AR density were increased in both genders after weight reduction, this effect being more marked in subc abdominal than in femoral adipocytes (P values ranging from 0.001 to 0.05). The alpha2-AR antilipolytic sensitivity was reduced in adipose cells from both regions in women, but only in subc abdominal adipocytes in men (P < 0.05), although the alpha2-AR density remained unchanged after weight reduction. In conclusion, a moderate weight loss leads to a higher adipose cell lipolytic efficiency which is associated with changes at receptor levels (mainly an increased beta2- and a decreased alpha2-AR sensitivities), in both genders.