Antimicrobial activity of clove oil dispersed in a concentrated sugar solution

Essential oil of clove, dispersed (0.4%v/v) in a concentrated sugar solution, had a marked germicidal effect against various bacteria and Candida albicans. Staphyloccus aureus (five strains), Klebsiella pneumoniae, Pseudomonas aeruginosa, Clostridium perfringens , and Escherichia coli inoculated at a level of 10⁷ cfu/ml, and C. albicans (inoculum 4.0×10⁵ cfu/ml) were killed (< 99.999%) after 2–7 min in a laboratory broth supplemented with 63% (v/w) of sugar, and containing 0.4% (v/w) of essential oil of clove. Added organic matter (i.e. human or bovine serum) did not impair its antimicrobial activity.
Sugar was not necessary for the antimicrobial activity of clove oil, but the concentrated sugar solution provided a good vehicle for obtaining an oil dispersion that is relatively stable for certain practical applications.     

Proteolytic degradation of HDL1 on the fat cell surface is nutritionally regulated

The importance of plasma HDL apolipoprotein concentration as a predictor of atherosclerotic risk is well recognized, yet the processes of HDL modification and degradation in various cells are not clearly understood. We examined the characteristics of HDL1 apolipoprotein degradation and cellular uptake by rat adipocytes and determined the effects of fasting on these processes. Epididymal and perirenal adipocytes were isolated from male Wistar rats (310 +/- 4 g) fed ad libidum and incubated with 5 micrograms of rat 125I-labeled HDL1 (d: 1.07-1.10 g/mL) mL-1 for 2 h at 37 degrees C. Cellular uptake of HDL1 was calculated as the trichloroacetic acid precipitable radioactivity associated with adipocytes following incubation. Intracellular and medium degradation of HDL1 were determined as trichloroacetic acid soluble 125I counts associated with cells and measured in the postincubation medium, respectively. Fifty to sixty percent of cellular uptake and degradation of HDL1 was inhibited by the addition of 25-fold excess unlabeled HDL. HDL1 degradation measured in the medium was 10- to 12-fold greater than cellular uptake of HDL1 apolipoproteins. Intracellular degradation of HDL1 was negligible. The presence of EDTA in the incubation medium reduced HDL1 degradation measured in the medium, but enhanced HDL1 cellular uptake. Conditioned medium separated from cells after 2 h of incubation at 37 degrees C in the absence of HDL and subsequently incubated with 125I-labeled HDL1 for an additional 2 h at 37 degrees C, degraded less than 5% of HDL compared with degradation in the presence of cells. These results suggest that rat adipocytes degrade, or modify, HDL1 particles, possibly by interactions with cell surface proteases.(ABSTRACT TRUNCATED AT 250 WORDS)     

Seed bank versus seed rain in the regeneration of a tropical pioneer tree

Summary We used the tropical pioneer tree, Cecropia obtusifolia to evaluate the relative importance of different sources of seeds in the regeneration of species that depend on ephemeral sites. We studied seed production in a population established in a 5 ha plot, and dispersal, dormancy and seed predation in two recent treefall gaps (<1 year-old), two building or successional forest patches (10–15 since disturbed), and two mature forest patches (>35 years since disturbed) for a one year period at Los Tuxtlas (Mexico). Flowers and fruits were counted at monthly intervals. Annual fecundity per tree ranged from 1.4×10⁴ to 1.4×10⁷ seeds. Seeds were continuously available on the trees and on the ground. Average annual seed rain per m² (as measured by 0.5×0.5 m seed traps) varied from 184 to 1925 among the six sites. Distance to nearest seed source and patch type explained more than 60% of the seed rain variation among sites. Soil seed density, estimated by counting seeds from ten samples (78.5 cm²×10 cm deep) collected from each site in October and January, ranged among the six sites from 269 to 4485 seeds per m² in January and from 204 to 5073 in October. Soil seed viabilities were much lower (17.1% in October and 5.1% in January) than those of rain seeds (48.26%). Annual survivorships of 2.2% were estimated for seeds artificially sown on the soil surface of a gap and a mature patch, and 3.75% in a building patch. In two other experiments seed removal rates ranged from 27% to 98% in 4 days. Removal rates were significantly higher in gap and mature patches than in building patches. Ants (Paratrechina vividula) and grasshopper nymphs (Hygronemobius. sp.) were the main predators. We draw three main conclusions from our data: (1) Pathogens and predators determine low survivorship of C. obtusifolia's seeds in the soil and a rapid turnover rate (1.07 to 1.02 years) of its seed bank; (2) a continuous and copious seed production and an abundant and extensive seed rain replenish the soil seed pool in patches with different disturbance ages at least up to 86 m from nearest source; (3) more than 90% of the seeds contributing to C. obtusifolia seedling recruitment in gaps are less than one year-old. We discuss our results in the context of previous similar studies for tropical forests.     

Potent slow-binding inhibition of cathepsin B by its propeptide.

A peptide (PCB1) corresponding to the proregion of the rat cysteine protease cathepsin B was synthesized and its ability to inhibit cathepsin B activity investigated. PCB1 was found to be a potent inhibitor of mature cathepsin B at pH 6.0, yielding a Ki = 0.4 nM. This inhibition obeyed slow-binding kinetics and occurred as a one-step process with a k1 = 5.2 x 10(5) M-1 s-1 and a k2 = 2.2 x 10(-4) s-1. On dropping from pH 6.0 to 4.7, Ki increased markedly, and whereas k1 remained essentially unchanged, k2 increased to 4.5 x 10(-3) s-1. Thus, the increase in Ki at lower pH is due primarily to an increased dissociation rate for the cathepsin B/PCB1 complex. At pH 4.0, the inhibition was 160-fold weaker (Ki = 64 nM) than at pH 6.0, and the propeptide appeared to behave as a classical competitive inhibitor rather than a slow-binding inhibitor. Incubation of cathepsin B with a 10-fold excess of PCB1 overnight at pH 4.0 resulted in extensive cleavage of the propetide whereas no cleavage occurred at pH 6.0, consistent with the formation of a tight complex between cathepsin B and PCB1 at the higher pH. The synthetic propeptide of cathepsin B was found to be a much weaker inhibitor of papain, a structurally similar cysteine protease, and no pH dependence was observed. Inhibition constants of 2.8 and 5.6 microM were obtained for papain inhibition by PCB1 at pH 4.0 and 6.0, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)     

Production of hydrogen peroxide by aryl-alcohol oxidase from the ligninolytic fungusPleurotus eryngii

Summary Production of extracellular hydrogen peroxide by fungal oxidases is been investigated as a requirement for lignin degradation. Aryl-alcohol oxidase activity is described in extracellular liquid and mycelium ofPleurotus eryngii and studied under non-limiting nitrogen conditions. This aryl-alcohol oxidase catalyses conversion of primary aromatic alcohols to the corresponding aldehydes and H₂O₂, showing no activity with aliphatic and secondary aromatic alcohols. The enzyme is stable at pH 4.0–9.0, has maximal activity at 45°–50°C and pH 6.0–6.5, is inhibited by Ag⁺, Pb²⁺ and NaN₃, and has aK _m of 1.2 mM using veratryl alcohol as substrate. A single protein band with aryl-alcohol oxidase activity was found in zymograms of extracellular and intracellular crude enzyme preparations fromP. eryngii.     

Substrate-dependent degradation patterns in the decay of wheat straw and beech wood by ligninolytic fungi

Summary The ability of 45 fungal strains to degrade wheat straw and beech wood was studied. Degradation patterns were defined in terms of chemical evolution of substrates and changes in lignin and polysaccharides. Trametes versicolor produced an important degradation of lignin and increased substrate digestibility, but it caused high weight losses and gave rise to similar decay patterns on both substrates. A preferential degradation of lignin was produced during straw transformation by Pleurotus eryngii. The increase of soluble lignin and decreases of lignin content and H/C ratio defined the degradation tendency after principal component analysis. The cation exchange capacity and water and alkali solubility presented the highest loading factors for the characterization of fungal transformation of beech wood. Offprint requests to: A. T. Martínez     

Polymerization of τ into Filaments in the Presence of Heparin: The Minimal Sequence Required for τ - τ Interaction

Abstract: Paired helical filaments isolated from the brains of patients with Alzheimer's disease are composed of a major protein component, the microtubule-associated protein termed τ, together with other nonprotein components, including heparan, a glycosaminoglycan, the more extensively sulfated form of which is heparin. As some of these nonprotein components may modulate the assembly of τ into filamentous structures, we have analyzed the ability of the whole τ protein or some of its fragments to self-assemble in the presence of heparin. Different τ fragments, all of them containing some sequences of the tubulin-binding motif, can assemble in vitro into filaments. We have also found formation of polymers with the 18-residue-long peptide corresponding to the third tubulin-binding motif of τ. This suggests that the ability of τ for self-assembly could be localized in a short sequence of amino acids present in the tubulin-binding repeats of the τ molecule.     

Physiological studies and determination of chromosome number in Maca,Lepidium Meyenii (Brassicaceae)

Experiments based on four accessions of maca (Lepdium meyenii) disclosed higher developmental rates in plants grown in neutral pH (6.6) soil when compared with those grown in acidic soil (5.3). Photoperiod response studies revealed similar growth rate for plants grown under either long day or short day condition. Plants in the field and growth chambers completed their life cycle in 11 months or less, therefore maca can be considered an annual crop. These results suggest that the range of adaptation of maca is not as narrow as previously believed, and therefore it can be successfully produced outside its natural habitat. Chromosome counts and predominance of bivalents in diakinesis and metaphase I disclosed that maca is a disomic octoploid of 2n=8x=64 chromosomes. Field and growth chamber observations and morphological uniformity of the plants within accessions indicate that maca relies mainly on self-fertilization for its reproduction.