Pentoxifylline

Pentoxifylline (PTX), a tri-substituted purine and xanthine derivative, has been used for several years to improve microcirculation because of its hemorheological properties. PTX has also antifibrotic and anti-inflammatory effects. We studied the reaction of PTX with the hydroxyl radical and superoxide anion. Hydroxyl radical was generated by a mixture of ascorbic acid, H₂O₂ and Fe (III)-EDTA. We evaluated the iron-dependent degradation of deoxyribose, mediated by hydroxyl radical, in the presence of different concentrations of PTX (from 0.05 to 3 mM), measuring the degradation products of deoxyribose that react with 2-thiobarbituric acid (TBA). The reaction of PTX with hydroxyl radical occurred with a rate constant of (1.1±0.2)×10¹⁰ M ⁻¹/s. These results support the properties of PTX as a hydroxyl radical scavenger. Some authors verified that PTX decreases the release of superoxide anion from activated neutrophils. We studied the effect of PTX as a scavenger of superoxide generated in vitro by a hypoxanthine-xanthine oxidase system. PTX was not a superoxide anion scavenger in this system.     

Age structure,growth and reproduction ofRutilus lemmingii in an intermittent stream of the Guadalquivir river basin,southern Spain

The age, growth and reproduction ofRutilus lemmingii (Steindachner, 1866), an endemic cyprinid from the Iberian Peninsula, was studied for over a period of two years in a small seasonal tributary of the Guadalquivir river basin. Approximately 65 % of the total growth in length occured in the first year of life. Males reached a maximum age of 3+ yr (Fork Length, F.L. = 114 mm) and females 4+ yr (F.L. = 144 mm). Both sexes matured during their second year of life (1 +). The overall sex ratio (334 males to 389 females) differed significantly from unity. Somatic condition decreased markedly during the reproductive period of March to May.R. lemmingii is a multiple spawner and releases two batches of eggs per female each year. Mean egg diameter of the first batch was larger than the second one. The regression between fecundity and Fork Length (mm) was: Fec = 0.014 F.L.Z.^2.858 Compared with available information, thisR. lemmingii population, located at a lower latitude, is characterized by fast growth, early maturity, high level of reproductive effort, and a short life-span. These life-history characteristices are typical of species in unstable environments, where adult mortality is high, variable or unpredictable.     

A new survey of Brazilian marine algae for agglutinins

Aqueous protein extracts from 30 Brazilian marine algae were examined for haemagglutinating activity using native and enzyme-treated rabbit, chicken, sheep and human erythrocytes. Most extracts agglutinated at least one of the blood cells used. Sheep and rabbit erythrocytes were more suitable for detection of the agglutinating activity. The minimum protein concentration necessary to produce positive agglutination was usually lower with enzyme-treated erythrocytes than native ones. The five algal protein extracts showing the greatest haemagglutination titre were tested for sugar-binding specificity. Only the activity present in the green alga Cauler pacupressoides was inhibited by simple sugars and not by the glycoproteins tested. The activity of the other four extracts was inhibited by at least one of the glycoproteins utilised. This revised version was published online in August 2006 with corrections to the Cover Date.     

Monte Carlo Study of Structural and Thermodynamic Properties of Liquid Chloroform Using a Five Site Model

A five site potential model combining Lennard–Jones plus Coulomb potential functions has been developed for chloroform molecule. The partial charges needed for Coulombic interactions were derived using the chelpg procedure implemented in the gaussian 92 program. These calculations were performed at the MP2 level with MC-311G* basis set for Cl and 6-311G** for C and H atoms. The parameters for the Lennard–Jones potentials were optimized to reproduce experimental values for the density and enthalpy of vaporization of the pure liquid at 298 K and 1 atm. The statistical mechanics calculations were performed with the Monte Carlo method in the isothermic and isobaric (NpT) ensemble. Besides the values obtained for density, ρ, and molar enthalpy of vaporization at constant pressure, Δ H_V, for liquid chloroform, results for molar volume, V_m, molar heat capacity, C_p, isobaric thermal expansivity, α_p, and isothermal compressibility, κ_T, for this pure liquid are also in very good agreement with experimental observations. Size effects on the values of thermodynamic properties were investigated. The potential model was also tested by computing the free energy for solvating one chloroform molecule into its own liquid at 298 K using a statistical perturbation approach. The result obtained compares well with the experimental value. Site–site pair correlation functions were calculated and are in good accordance with theoretical results available in the literature. Dipole–dipole correlation functions for the present five site model were also calculated at different carbon–carbon distances. These correlations were compared to those obtained using the four site model reported in the literature. An investigation of the solvent dependence of the relative free energy for cis/trans conversion of a hypothetical solute in TIP4P water and chloroform was accomplished. The results show strong interaction of water and chloroform molecules with the gauche conformer. The value obtained for the free energy barrier for cis/trans rotation in TIP4P water is higher than that for chloroform. This result is in agreement with the continuous theory for solvation as the conformer with higher dipole moment is more favoured by the solvent with higher dieletric constant. The results also show an increase in entropy as the solute goes from the cis to the trans geometry and this result is more appreciable in the aqueous solution. This revised version was published online in June 2006 with corrections to the Cover Date.     

Expression of novel genes linked to the androgen-induced, proliferative shutoff in prostate cancer cells

Androgens control cell numbers in the prostate through three separate pathways: (a) inhibition of cell death, (b) induction of cell proliferation (Step-1) and (c) inhibition of cell proliferation (Step-2, proliferative shutoff). The mechanisms underlying these phenomena are incompletely understood. The human prostate carcinoma LNCaP variants express these pathways as follows: LNCaP-FGC express both steps, LNCaP-LNO expresses Step-2, LNCaP-TAC expresses Step-1, and LNCaP-TJA cells express neither step. These cells facilitated the search for mediators of the androgen-induced proliferative shutoff pathway. Androgen exposure for 24 h or longer induced an irreversible proliferative shutoff in LNCaP-FGC cells. The Wang and Brown approach for identifying differentially expressed mRNAs was used to search for mediators of Step-2. Ten unique inserts were identified and from those ten, three genes were further studied. The basal expression of these genes in shutoff-negative variants was not affected by androgen exposure. They were induced by androgens in shutoff-positive LNCaP variants and the androgen receptor-transfected, shutoff-positive, MCF7-AR1 cells. These genes were induced only in the range of androgen concentrations that elicited the shutoff response. Time course analysis showed that their induction precedes the commitment point by 12–18 h. In addition, they were expressed in the normal prostate during proliferative shutoff. These features suggest that the candidate genes have a role in the regulation cascade for proliferative shutoff.     

Hydrological cycle and interannual variability of the aquatic community in a temporary saline lake (Fuente de Piedra,Southern Spain)

Fuente de Piedra is a shallow, temporary saline lake whoseseasonal behavior is strongly dependent on the annual hydrologicalbudget. In this study, we outline the characteristics of Fuente dePiedra Lake for two years that had different hydrological budgets.The high precipitations in 1989–90 caused the lake not to dry asusual, and decreased both salinity and the amplitude of changes.There were also differences in nutrient dynamics, with generallylower concentrations of soluble reactive phosphorus and ammonium,whereas in the more humid year nitrate showed a distinct maximum inwinter. Winter bloom chlorophyll a concentrations were alsomuch higher in 1989–90 (>600 g l-1) but there wasalso a winter productive phase that was presumably poorly coupledwith consumption processes that predominate in spring. Planktonicassemblages were different between years. Highly halotolerantphytoplankton species (Dunaliella salina and D. viridis) became scarcer, and especially two previouslyunrecorded diatoms (Cyclotella sp. and Chaetoceros sp.)became dominant in the bloom time in the wet year. The speciesrichness of the zooplankton increased in the wet year, with newspecies appearing that were not collected during 1987–88(Branchinectella media, Daphnia mediterranea, Macrothrix sp.,Arctodiaptomus salinus, Cyclops sp., Sigara sp...).There was also a much higher development of macrophytes (Ruppiadrepanensis, Althenia orientalis, Lamprothamnium papulosum)and bird populations, especially flamingoes (Phoenicopterusruber).Important interannual variations in this sort of system pointto the need for long term studies to observe the whole range ofstates that define the lake as an entity.     

RTN TRH causes prolonged respiratory stimulation

Cream, Carlos L., Aihua Li, and Eugene E. Nattie. RTNTRH causes prolonged respiratory stimulation. J. Appl.Physiol. 83(3): 792-799, 1997.We injectedthyrotropin-releasing hormone (TRH; 10 nl; 0.25, 0.5, 1.0, or 10 mM),its inactive free acid form (TRHOH; 1 mM), or a metabolite with lowTRH-receptor binding affinity, histidine-proline diketopiperazine (cHP;1 mM), into the retrotrapezoid nucleus of anesthetized rats. Injectionlocation was verified by anatomic analysis. Lower doses (0.25-0.5mM) significantly increased both the product of integrated phrenicamplitude and frequency(Phr · f) and f for 20-30min compared with artificial cerebrospinal fluid control injections. Higher doses (1.0-10 mM) produced greater and long-lastingstimulation of Phr · f,Phr, and f and of blood pressure. Thisstimulation reached values 150% of baseline and durations of 270 minafter a single injection. TRHOH (1 mM ) or cHP (1 mM) had no effect onPhr but increased f, as did 1 mM TRH. We concludethat TRH has a very powerful stimulatory effect in the retrotrapezoidnucleus region on Phr · f, withthe Phr response seemingly specific for TRHreceptors. Similar responses of f to TRHOH and cHP suggest it may benonspecific.

     

Chromosome-encoded inducible copper resistance inPseudomonas strains

NinePseudomonas strains were selected by their high copper tolerance from a population of bacteria isolated from heavy-metal polluted zones. Copper resistance (Cu ^r ) was inducible by previous exposure of cultures to subinhibitory amounts of copper sulfate. All nine strains possessed large plasmids, but transformation and curing results suggest that Cu ^r is conferred by chromosomal genes. Plasmid-lessPseudomonas aeruginosa PAO-derived strains showed the same level of Cu ^r as environmental isolates and their resistance to copper was also inducible. Total DNA from the environmentalPseudomonas, as well as fromP. aeruginosa PAO strains, showed homology to a Cu ^r P. syringae cop probe at low-stringency conditions but failed to hybridize at high-stringency conditions.     

Composition and properties of Albizia lebbeck gum exudate

An analytical study has been made of six gum specimens from Albizia lebbeck, Leguminosae. Galactose, mannose, arabinose, glucuronic acid and its 4-O--metyl analogue are present in all the specimens studied. Rhamnose was not detected according to sugar analysis and spectral data. The absence of this sugar, the high acidity and the relatively low limit viscosity number contrast with the values reported previously for one African sample of A. lebbeck. The lead content is much higher than that recorded for other Albizia gums. ¹³C-NMR spectrum of this gum, in deuterium oxide, shows good resolution.