A complex plant cell wall polysaccharide: rhamnogalacturonan II. A structure in quest of a function

Walls of growing plants are extremely complex and sophisticated composite materials incorporating a dynamic assembly of polysaccharides, proteins and phenolics. Among the polysaccharides, the pectins encompass a group of acidic heteropolysaccharides; they offer a repertoire of structural complexity associated with the occurrence of, at least, three specific domains. Whereas most of these domains are notable for their structural heterogeneity, one of these, the so-called rhamnogalacturonan II (RG-II) exhibits a remarkable conservation throughout the plant kingdom. RG-II is thought to be the most complex plant polysaccharide on Earth (MW 5-10 kDa); its occurrence and strong conservation may indicate that it plays a major role in the structure and growth of higher plants. The present paper examines the most recent findings related to the occurrence, the structures, biosynthesis, biological role and properties, functional properties and technological applications of RG-II. Particular emphasis is given on the description of the three-dimensional structures of RG-II, in its monomeric and dimeric form as elucidated from the concerted investigations throughout 800 MHz NMR spectroscopy, light scattering, atomic force microscopy along with molecular mechanics and dynamics. Some attempts of deciphering of the structural role that RG-II may play in the cell wall of growing plants are presented.

Cerebrospinal fluid and plasma concentrations of nitric oxide metabolites are increased in dementia with Lewy bodies

We compared cerebrospinal fluid (CSF) and plasma concentrations of nitric oxide metabolites (NO(-)(x)) in 22 patients with dementia with Lewy bodies (DLB) and 13 matched controls. We found a pronounced increase in NO(-)(x) CSF and plasma levels in DLB patients. No changes were found in L-arginine and L-citrulline levels in CSF or plasma. There was no correlation between CSF and plasma levels and age, age of onset, duration of the disease or scores of the MiniMental State Examination. These findings reveal that excessive nitric oxide production may be related to the pathogenesis of DLB.

Serum levels of coenzyme Q in patients with Lewy body disease

The purpose of the present study was to compare serum levels of coenzyme Q(10) (CoQ(10)) and the coenzyme Q(10) cholesterol (CoQ(10)/cholesterol) ratio in 18 patients with Lewy body disease (LBD) with 20 matched controls. The mean serum coenzyme Q10 levels in patients with LBD were significantly reduced with respect to control group, however, no differences were found in CoQ(10)/cholesterol ratio between LBD patients and control group. There was no correlation among CoQ(10) and CoQ(10)/cholesterol ratio with age, age of onset, body mass index, duration of the disease or scores of the Mini Mental State Examination, UPDRS and Hoehn and Yahr stage. These results suggest the involvement of this enzimatic system in the pathogenic mechanism of LBD.

New 3-[4-(3-substituted phenyl)piperazin-1-yl]-1-(benzo[b]thiophen-3-yl)propanol derivatives with dual action at 5-HT1A serotonin receptors and serotonin transporter as a new class of antidepressants

In this paper a series of new 3-[4-(3-substituted phenyl)piperazin-1-yl]-1-(benzo[b]thiophen-3-yl)propanol derivatives is presented as a new class of antidepressant drugs with dual activity at 5-HT1A serotonin receptors and serotonin transporter. The 5-HT1A receptor and 5-HT transporter binding affinities of hydroxylic compounds 4 a-e have been determined. The new compounds present nanomolar affinity for both activities, and 1-(benzo[b]thiophen-3-yl)-3-[4-(3-methoxyphenyl)piperazin-1-yl]propan-1-ol (4d) shows values (nM) of Ki = 86 for 5-HT1A receptors and Ki = 76 for the serotonin transporter, respectively.

New 3-[4-(aryl)piperazin-1-yl]-1-(benzo[b]thiophen-2-yl)propane derivatives with dual action at 5-HT1A serotonin receptors and serotonin transporter as a new class of antidepressants

Some benzo[b]thiophene derivatives with different substituents in positions 3 and 5 have been synthesized in order to obtain new dual antidepressant drugs. Compounds derived from 2-acetyl-3-methylbenzo[b]thiophene or 2-acetyl-3,5-dimethylbenzo[b]thiophene were prepared with two different phenylpiperazines (2-methoxy and 2-hydroxyphenylpiperazine) and evaluated for in vitro 5-HT1A receptor affinity and serotonin reuptake inhibition by radioligand assays. Compound 1-(3,5-dimethylbenzo[b]thiophen-2-yl)-3-[4-(2-methoxyphenyl)piperazin-1- yl]propan-1-ol (II.2.a) shows good values (nM) for both activities: Ki = 85 for 5-HT1A receptor and Ki = 120 for serotonin transporter.

Extremity and whole-body dosemeters for beta and beta gamma fields based on LiF:Mg,Cu,P thin detectors

This study aims at proposing two TL dosemeters: one for the whole body and another for the extremities, for beta and gamma fields. Selected sensible material consists of 5 mg x cm(-2) LiF:Mg,Cu,P film (GR-200F) manufactured in China. Calibration was carried out according to ISO 4037-3, in terms of Hp(0.07), and dosimetric performance was analysed on the basis of IEC-1066 and ISO-12794 Standards. Experiments showed a satisfactory sensitivity of the proposed dosemeters for detecting beta radiation at protection levels and a very good energy response; thus, highly recommending their use for weakly penetrating radiation measurements. However, the homogeneity and the reproducibility of GR-200F are not found to be as reliable as in standard materials.

Quantitative analysis of polycyclic aromatic hydrocarbons in sewage sludge from wastewater treatment plants

Polycyclic aromatic hydrocarbons (PAHs) are an important group of organic contaminants present in sewage sludge. Due to their persistence and toxic potential, information about their presence in sewage sludge is needed in order to assess applicability on agricultural land. A method for the gas chromatographic-mass spectrometric (GC-MS) determination was developed and applied to the trace determination of PAHs present in sewage sludge samples from six wastewater treatment plants (WWTPs) differing in the type of treatment and the origin of wastewater. PAHs were extracted from freeze-dried samples by a dichloromethane-methanol (2:1) mixture in a sonication bath. The sludge extracts were cleaned-up by an alumina column. The method showed recovery values varying from 60 to 98%. Four surrogate standards ([2H8]naphthalene, [2H10]anthracene, [2H12]benzo[a]anthracene, and [2H12]benzo[ghi]perylene) were used for quantitation by GC-MS. A reference sludge sample was analysed in order to validate the method. The sum of the 16 US Environmental Protection Agency PAHs analysed in the sewage sludge samples varied from 1.13 to 5.52 mg/kg. No significant difference between the different WWTPs was found.

The diluted aqueous solvation of carbohydrates as inferred from molecular dynamics simulations and NMR spectroscopy

The purpose of this paper is to review our understanding of the dilute hydration (aqueous solvation) behaviour of disaccharide compounds. To this end we discuss and scrutinize the results that have been obtained for the three model disaccharides: maltose, sucrose and trehalose from experimental NMR studies and from theoretical molecular dynamics studies in explicit aqueous solutions. The focus is on the description of molecular hydration features that will influence macroscopic entities such as diffusion and relaxation: residence times of hydration waters, hydration numbers and hydration densities. The principles of molecular dynamics simulation are briefly outlined while a detailed presentation is given of the key features that characterise hydration: the solvation of the glycosidic linkage, the radial hydration of the solute, the water density anisotropy around the solute, the residential behaviour of water molecules in the periphery of the solute, and rotational and translational diffusion coefficients. With respect to the use of NMR in characterising the structure and dynamics of the hydration, the hydrodynamic theory of rotational and translational diffusion of biomolecules as well as the use of pulse field gradient spin echo experiments are briefly presented. The NMR-defined rotational diffusion coefficients (D(r)) and the experimentally determined translational diffusion (D(t)) coefficients are reported for 4% (w/w) solutions of sucrose, trehalose and maltose. These results are compared with theoretical data obtained from molecular dynamics simulations of sucrose, trehalose and maltose under identical conditions (concentration, temperature, etc.). With our present level of knowledge we can propose that although carbohydrates share a number of hydration characteristics, evidence is accumulating in support of the notion that it is not the amount or overall hydration but rather the detailed individual carbohydrate-water interaction that is likely to determine carbohydrate structure and functionality.

[Neuroretinal rim width in normal, hypertensive and glaucomatous subjects]

PURPOSE

To determine width and shape of neuro-retinal rim in normal hypertensive subjects and patients with glaucomatous damage.

MATERIAL AND METHOD

Patients underwent a perimetry and a photographic retinal nerve fiber evaluation. Patients were divided in three groups: normal subjects (n=34), ocular hypertension subjects (n=38) and glaucoma patients (n=34). Neuro-retinal rim was measured using 40 degrees stereoscopic photographs with center in the optic nerve head based on a biomorphometry technique.

RESULTS

In normal subjects neuro-retinal rim appeared wider in the lower pole, followed by the upper, nasal and temporal aspects. Optic nerve fiber layer showed a decreased thickness in hypertensive and glaucoma patients, particularly in sectors of the temporal aspect of the optic nerve (p<0.05).

CONCLUSIONS

A Planimetry study of the optic nerve is able to detect alterations in normal neuro-retinal rim configuration and can as well detect thinning of the rim, particularly in temporal, upper and lower areas.

Occurrence of polycyclic aromatic hydrocarbons in sewage sludge and their contribution to its toxicity in the toxalert 100 bioassay

The contribution of polycyclic aromatic hydrocarbons (PAH) present in sewage sludge samples to toxicity was investigated. Chemical analysis using gas chromatography mass spectrometry (GC-MS) and the ToxAlert 100 bioassay, based on the inhibition to Vibrio fischeri, were applied to sludge extracts after purification by column chromatography. The levels of the 16 US EPA PAH analyzed in the sewage sludge samples varied from 17 to 2,030 microg kg(-1). In all samples examined phenanthrene was the most prominent compound. The toxicity data obtained by ToxAlert 100 can be explained by the levels and composition of the different PAH in sewage sludge samples. The present approach can contribute to evaluate the toxicity of sewage sludge.

Platelet activating factor increases ciliary activity in the hamster oviduct through epithelial production of prostaglandin E2

We investigated the signal transduction mechanisms associated with an increase in ciliary beat frequency (CBF) produced by platelet activating factor (PAF) in oviductal ciliated cell cultures. In the range of concentrations similar to that produced by preimplantation embryos, PAF increased the CBF in a dose-dependent manner. The addition of PAF and prostaglandin E2 (PGE2) to the cultures produced a synergic increase of ciliary beating, suggesting that PAF and PGE2 signal transduction pathways may be associated. To demonstrate this hypothesis, cyclooxygenase-2 (COX-2) was selectively blocked by a specific inhibitor, NS-398, and the PAF-induced CBF increase was abolished. Moreover, a phospholipase A2 (PLA2) inhibitor, AACOCF3, blocks the PAF-induced CBF increase. PGE2 production by oviductal epithelial cells is stimulated by PAF, and WEB-2086, a PAF-receptor blocker, specifically blocks the PAF-induced PGE2 production. Using the fluorescent indicator fura-2, we measured the effect of PAF on intracellular Ca2+ concentration ([Ca2+]i) in individual ciliated cells. PAF induced a transient increase of [Ca2+]i that was blocked by WEB-2086 or by removal of extracellular Ca2+. We propose a mechanism for PAF-mediated signal transduction in the ciliated cells of the oviductal epithelium. Minimal doses of PAF trigger Ca2+ mobilization in tandem with increased PLA2 activity and a COX-2-mediated increase in PGE2. Local PGE2 production by the oviductal mucosa suggests the presence of an autocrine loop controlling ciliary activity.

Experimental proof for the structure of a thrombin-inhibiting heparin molecule

Kinetic studies of thrombin inhibition by antithrombin in the presence of heparin have shown that thrombin binds to heparin in a preformed heparin-antithrombin complex. To study the relative position of the thrombin binding domain and the antithrombin binding domain on a heparin molecule we have designed and synthesized heparin mimetics, which structurally are very similar to the genuine polysaccharide. Their inhibitory properties with respect to factor Xa and thrombin provide experimental evidence that in heparin the thrombin binding domain must be located at the nonreducing end of the antithrombin binding domain to observe thrombin inhibition. As expected, factor Xa inhibition is not affected by elongation of the antithrombin binding pentasaccharide sequence, regardless of the position in which this elongation takes place.

Experimental observation of noise precursors for virtual Hopf phenomena near period-doubling bifurcations in modulated diode lasers

We present an experimental analysis of the effect of a rf amplitude modulation of the injection current in a distributed-feedback diode laser at 1.55 mum near the first period-doubling bifurcation. First experimental results of a virtual Hopf phenomenon were observed when two moving bumps with Lorentzian shapes appeared in the spectrum before the onset of the first period-doubling bifurcation occurred. We characterized this observation by increasing the amplitude of the current modulation of the diode laser until period-doubling bifurcation took place. The shape and position in the spectrum of these Lorentzian bumps were studied by the noise precursors theory, which predicts that the presence of noise will act as a virtual Hopf precursor in systems undergoing a period-doubling bifurcation.

New 3-[4-(aryl)piperazin-1-yl]-1-(benzo[b]thiophen-3-yl)propane derivatives with dual action at 5-HT1A serotonin receptors and serotonin transporter as a new class of antidepressants

A series of new 3-[4-(aryl)piperazin-1-yl]-1-(benzo[b]thiophen-3-yl)propane derivatives were synthesized in an attempt to find a new class of antidepressant drugs with dual activity at 5-HT1A serotonin receptors and serotonin transporter. Title compounds were evaluated for in vitro activity on 5-HT1A receptor and 5-HT transporter. They show high nanomolar affinity for both activities, and in particular, compounds 1-(5-chlorobenzo[b]thiophen-3-yl)-3-[4-(2-methoxyphenyl)piperazin-1-yl]propan-1-ol (7) and 1-(5-fluorobenzo[b]thiophen-3-yl)-3-[4-(2-methoxyphenyl)piperazin-1-yl]propan-1-ol (8) show values (nM) of K(i)=30 and 2.3 for 5-HT1A receptors and K(i)=30 and 12 for serotonin transporters, respectively. In GTPgammaS binding assays, compound 8 revealed antagonist properties to 5-HT1A receptors. Such a pharmacological profile could lead to potent antidepressant agents with new dual mechanism of action.

X-ray structure determination and modeling of the cyclic tetrasaccharide cyclo

The cyclic tetrasaccharide cyclo-[-->6)-alpha-D-Glcp-(1-->3)-alpha-D-Glcp-(1-->6)-alpha-D-Glcp-(1-->3)-alpha-D-Glcp-(1-->] is the major compound obtained by the action of endo-alternases on the alternan polysaccharide. Crystals of this cyclo-tetra-glucose belong to the orthorhombic space group P2(1)2(1)2(1) with a = 7.620(5), b = 12.450(5) and c = 34.800(5) A. The asymmetric unit contains one tetrasaccharide together with five water molecules. The tetrasaccharide adopts a plate-like overall shape with a very shallow depression on one side. The shape is not fully symmetrical and this is clearly apparent on comparing the (phi, psi) torsion angles of the two alpha-(1-->6) linkages. There is almost 10 degrees differences in phi and more than 20 degrees differences in psi. The hydrogen bond network is asymmetric, with a single intramolecular hydrogen bond: O-2 of glucose ring 1 being the donor to O-2 of glucose ring 3. These two hydroxyl groups are located below the ring and their orientation, dictated by this hydrogen bond, makes the floor of the plate. Among the five water molecules, one located above the center of the plate occupies perfectly the shallow depression in the plate shape formed by the tetrasaccharide. Molecular dynamics simulation of the tetrasaccharide in explicit water allows rationalization of the discrepancies observed between the X-ray structures and data obtained previously by NMR.

A priori crystal structure prediction of native celluloses

The packing of beta-1,4-glucopyranose chains has been modeled to further elaborate the molecular structures of native cellulose microfibrils. A chain pairing procedure was implemented that evaluates the optimal interchain distance and energy for all possible settings of the two chains. Starting with a rigid model of an isolated chain, its interaction with a second chain was studied at various helix-axis translations and mutual rotational orientations while keeping the chains at van der Waals separation. For each setting, the sum of the van der Waals and hydrogen-bonding energy was calculated. No energy minimization was performed during the initial screening, but the energy and interchain distances were mapped to a three-dimensional grid, with evaluation of parallel settings of the cellulose chains. The emergence of several energy minima suggests that parallel chains of cellulose can be paired in a variety of stable orientations. A further analysis considered all possible parallel arrangements occurring between a cellulose chain pair and a further cellulose chain. Among all the low-energy three-chain models, only a few of them yield closely packed three-dimensional arrangements. From these, unit-cell dimensions as well as lattice symmetry were derived; interestingly two of them correspond closely to the observed allomorphs of crystalline native cellulose. The most favorable structural models were then optimized using a minicrystal procedure in conjunction with the MM3 force field. The two best crystal lattice predictions were for a triclinic (P(1)) and a monoclinic (P2(1)) arrangement with unit cell dimensions a = 0.63, b = 0.69, c = 1.036 nm, alpha = 113.0, beta = 121.1, gamma = 76.0 degrees, and a = 0.87, b = 0.75, c = 1.036 nm, gamma = 94.1 degrees, respectively. They correspond closely to the respective lattice symmetry and unit-cell dimensions that have been reported for cellulose Ialpha and cellulose Ibeta allomorphs. The suitability of the modeling protocol is endorsed by the agreement between the predicted and experimental unit-cell dimensions. The results provide pertinent information toward the construction of macromolecular models of microfibrils.

Structure/thermodynamics relationships of lectin-saccharide complexes: the Erythrina corallodendron case

Molecular dynamics (MD) simulations of Erythrina corallodendron lectin binding to a monosaccharide, alpha-galactose, and a disaccharide, N-acetyl lactosamine, have been performed in order to investigate the relationship between structure and thermodynamics. A simulated annealing protocol has been used to generate ensembles of structures for the two complexes, from which both qualitative and quantitative information on binding dynamics have been extracted. The ensembled averaged lectin-saccharide interaction enthalpy is equivalent for both sugars, whereas the calculation based on the X-ray structures does show a difference. Within large statistical errors, the calculated 'binding enthalpy' is also the same for the two systems. These errors arise largely from terms involving solvent and are a typical limitation of current MD simulations. Significant qualitative differences in binding between the two complexes are, however, observed over the ensembles. These could be important for unraveling the structure/thermodynamic relationship. Stated simply, there are a greater number of binding options available to the disaccharide compared to the monosaccharide. The implications of alternative binding states on thermodynamic parameters and the 'breaking of enthalpy-entropy compensation' are discussed. The role of solvent in lectin-saccharide complex formation is suggested to be significant.

An unusual carbohydrate binding site revealed by the structures of two Maackia amurensis lectins complexed with sialic acid-containing oligosaccharides

Seeds from the legume tree Maackia amurensis contain two lectins that can agglutinate different blood cell types. Their specificity toward sialylated oligosaccharides is unique among legume lectins; the leukoagglutinin preferentially binds to sialyllactosamine (alphaNeuAc(2-3)betaGal(1-4)betaGlcNAc), whereas the hemagglutinin displays higher affinity for a disialylated tetrasaccharide (alphaNeuAc(2-3)betaGal(1-3)[alphaNeuAc(2-6)]alphaG alNAc). The three-dimensional structure of the complex between M. amurensis leukoagglutinin and sialyllactose has been determined at 2.75-A resolution using x-ray crystallography. The carbohydrate binding site consists of a deep cleft that accommodates the three carbohydrate residues of the sialyllactose. The central galactose sits in the primary binding site in an orientation that has not been observed previously in other legume lectins. The carboxyl group of sialic acid establishes a salt bridge with a lysine side chain. The glucose residue is very efficiently docked between two tyrosine aromatic rings. The complex between M. amurensis hemagglutinin and a disialylated tetrasaccharide could be modeled from the leukoagglutinin/sialyllactose crystal structure. The substitution of one tyrosine by an alanine residue is responsible for the difference in fine specificity between the two isolectins. Comparison with other legume lectins indicates that oligosaccharide specificity within this family is achieved by the recycling of structural loops in different combinations.

[Food intake, dietary habits and nutritional status of the population of Reus (X): Evolution of the diet and the contribution of macronutrients to energy intake (1983-1999) by age and sex]

BACKGROUND

To study the evolution of the diet and the nutritional intake between 1983 and 1999, by age and sex.

SUBJECTS AND METHODS

We performed a series of analysis of the food intake on a representative sample of the population of Reus (aged 10-69 years). Dietary intake was estimated using the 24-hours recall method. In 1999 the sample size was 839 individuals, 41% of them having taken part in the studies since 1983. Results are shown as mean (standard deviation).

RESULTS

In 1999, the energy intake was 2524 (582) kcal in men aged 35-44 years (n = 57), and 1827 (490) kcal in women (n = 95) (p < 0.001 between sexes). The energy intake decreases with age (significant trend [p < 0.001] between 15-69 years) and it is higher in men than in women in all the age groups studied. When comparing similar age groups, we observe that this energy intake has not changed significantly since 1983. Between 1983 and 1999 the contribution of the macronutrients to the total energy intake has become more similar between ages and sexes. In 1999, in men aged 35-44 years a 15.6% of the energy came from proteins, 42% from fat and 42.5% from carbohydrates; in women of the same age: a 17.3% of the energy came from proteins, 42.4% from fat and 40.3% from carbohydrates). During this period we observed, however, remarkable changes in the diet which imply the increasing participation of the dairy products, vegetables and meat in the energy intake, or the significant decrease of the role of tubers, eggs and visible fat.

CONCLUSIONS

Our population maintains an energy intake without significant changes, and it presents a trend towards a progressive uniformity of the nutritional balance between the different ages and sexes, although there are significant changes in some components of the diet.

[Effect of topical pranoprofen on the lipoxygenase metabolism of the arachidonic and in endotoxin-induced uveitis]

PURPOSE

To study the antiinflammatory effect of topical pranoprofen on the lipoxygenase metabolism of the arachidonic acid in albino rabbits.

METHODS

Endotoxin-induced uveitis (EIU) was produced in albino rabbits by intravitreal injection in the right eye with 10 microg of Salmonella typhymurium lipopolysacharide A in 5 microl saline solution. We have used 5 groups of 12 animals each. Control group (G-I) was injected with 5 microl of saline solution and 5 microl of ET solution were injected in the remaining groups. Groups III, IV and V were treated with topical pranoprofen 2 hours before intravitreal injection, immediately after and every 6, 4 and 2 hours respectively. The animals were sacrificed 24 hours after the ET administration. Cellular and B4 leukotrien concentration in the aqueous humour was determined.

RESULTS

The groups treated with pranoprofen showed a significant decrease in the cellular concentration in relation to the group of endotoxin (G-II). We did not observe any difference in the B4 leukotriene concentration between ET group and topical pranoprofen groups.

CONCLUSION

Topical pranoprofen has not increased the lipoxygenase metabolism of the arachidonic acid.

Conformational behavior of hyaluronan in relation to its physical properties as probed by molecular modeling

Hyaluronan (HA) is a linear charged polysaccharide whose structure is made up of repeating disaccharide units. Apparently conflicting reports have been published about the nature of the helical structure of HA in the solid state. Recent developments in the field of molecular modeling of polysaccharides offer new opportunities to reexamine the structural basis underlying the formation and stabilization of ordered structures and their interactions with counterions. The conformational spaces available and the low energy conformations for the disaccharide, trisaccharide, and tetrasaccharide segments of HA were investigated via molecular mechanics calculations using the MM3 force field. First, the results were used to access the configurational statistics of the corresponding polysaccharide. A disordered chain having a persistence length of 75 A at 25 degrees C is predicted. Then, the exploration of the stable ordered forms of HA led to numerous helical conformations, both left- and right-handed, having comparable energies. Several of these conformations correspond to the experimentally observed ones and illustrate the versatility of the polysaccharide. The double stranded helical forms have also been explored and theoretical structures have been compared to experimentally derived ones.