Chromenes of polyketide origin from Peperomia villipetiola

An extract of leaves and stems of Peperomia villipetiola has been found to contain myristicin (3-methoxy-4,5-methylenedioxy-allylbenzene) and seven chromenes, whose structures are methyl 5-hydroxy-7-methyl-2,2-dimethyl-2H-1-chromene-6-carboxylate (1), methyl 5-methoxy-7-methyl-2,2-dimethyl-2H-1-chromene-8-carboxylate (2), methyl 7-hydroxy-5-methyl-2,2-dimethyl-2H-1-chromene-6-carboxylate (3), methyl 7-methoxy-5-methyl-2,2-dimethyl-2H-1-chromene-6-carboxylate (4), 5-methanol-7-hydroxy-2,2-dimethyl-2H-1-chromene-6-carboxylic acid (5), 5-methanol-7-methoxy-2,2-dimethyl-2H-1-chromene-6-carboxylic acid (6), and methyl 5-acetoxymethanol-7-hydroxy-2,2-dimethyl-2H-1-chromene-6-carboxylate (7). A biosynthetic rationale for 1-7 suggests that orsellinic acid may be a common intermediate. The anti-fungal activities of the chromenes were measured bioautographically against Cladosporium cladosporioides and Cladosporium sphaerospermum: compounds 6 and 7 were found to be the most active.     

Long range lateral root activity by neo-tropical savanna trees

The extent of water uptake by lateral roots of savanna trees in the Brazilian highlands was measured by irrigating two 2 by 2 m plots with deuterium-enriched water and assaying for the abundance of deuterium in stem water from trees inside and at several distances from the irrigation plots. Stem water of trees inside the irrigation plots was highly enriched compared to that of control trees, whereas stem water of trees just outside the plot was only slightly enriched compared with that from control trees. Therefore, bulk water uptake in the savanna trees studied occurred in a horizontally restricted area, indicating that their rooting structure was characterized by a dense cluster of short roots associated with the main trunk and a few meandering long range lateral roots. This root architecture was confirmed by extensive excavations of several species. The same deuterium labeling pattern was observed in an Amazonian tropical forest. The savanna ecosystem, however, differed from the tropical forest ecosystem by having a greater proportion of trees outside the irrigation plots having stem water with deuterium levels significantly above background. This leads us to the conclusion that savanna trees have more or longer lateral roots compared to tropical forest trees. The greater lateral root development in savanna trees may be an adaptation for more efficient nutrient absorption.     

Coenzyme Q and the regulation of intracellular steady-state levels of superoxide in HL-60 cells

The present work was set to study how CoQ concentrations affected steady-state levels of superoxide in a cellular model of partial CoQ(10) deficiency in cultured human myeloid leukemia HL-60 cells. Culturing HL-60 cells in the presence of p-aminobenzoate, a competitive inhibitor of polyprenyl-4-hydroxybenzoate transferase (Coq2p), produced a significant decrease of CoQ(10) levels without affecting cell viability. Concomitant decreases in CoQ-dependent electron transport activity and mitochondrial membrane potential were observed under these conditions. Intracellular superoxide was significantly elevated in cells treated with p-aminobenzoate, both under serum-containing and serum-free conditions, and this effect was reversed by exogenous CoQ(10). A slight increase of superoxide was also observed in CoQ(10)-supplemented cells in the absence of serum. Our results support a requirement for CoQ(10) to control superoxide levels in HL-60 cells. The importance of extramitochondrial sources of superoxide in cells with impaired CoQ(10) biosynthesis is discussed.     

Synthesis of tricyclic analogs of stephaoxocanidine and their evaluation as acetylcholinesterase inhibitors

The synthesis of simplified analogs of the novel isoquinoline alkaloid stephaoxocanidine, carrying the oxazaphenalene ABC-ring system of the natural product, and their activity as inhibitors of the enzyme acetylcholinesterase, are reported. 5,6-Dimethoxy-7H -8-oxa-1-aza-phenalen-9-one (5) was as active as a Narcissus extract enriched in galantamine.     

Circular dichroism of pig and bovine lactadherins and their affinity for the pig zona pellucida

We have purified and characterized pig and bovine milk lactadherins. Studies by circular dichroism spectroscopy indicate that the two proteins present a similar folding pattern. Results have been discussed in terms of their affinity for pig zona pellucida in order to use these proteins as analogs of pig sperm lactadherin in gamete studies.     

Water uptake and transport in lianas and co-occurring trees of a seasonally dry tropical forest

Water uptake and transport were studied in eight liana species in a seasonally dry tropical forest on Barro Colorado Island, Panama. Stable hydrogen isotope composition (D) of xylem and soil water, soil volumetric water content (_v), and basal sap flow were measured during the 1997 and 1998 dry seasons. Sap flow of several neighboring trees was measured to assess differences between lianas and trees in magnitudes and patterns of daily sap flow. Little seasonal change in _v was observed at 90–120 cm depth in both years. Mean soil water D during the dry season was –19 at 0–30 cm, –34 at 30–60 cm, and –50 at 90–120 cm. Average values of xylem D among the liana species ranged from –28 to –44 during the middle of the dry season, suggesting that water uptake was restricted to intermediate soil layers (30–60 cm). By the end of the dry season, all species exhibited more negative xylem D values (–41 to –62), suggesting that they shifted to deeper water sources. Maximum sap flux density in co-occurring lianas and trees were comparable at similar stem diameter (DBH). Furthermore, lianas and trees conformed to the same linear relationship between daily sap flow and DBH. Our observations that lianas tap shallow sources of soil water at the beginning of the dry season and that sap flow is similar in lianas and trees of equivalent stem diameter do not support the common assumptions that lianas rely primarily on deep soil water and that they have higher rates of sap flow than co-occurring trees of similar stem size.     

Identification of the infectious source of an unusual outbreak of histoplasmosis, in a hotel in Acapulco, state of Guerrero, Mexico

Three isolates of Histoplasma capsulatum were identified from mice lung, liver, and spleen inoculated with soil samples of the X hotel's ornamental potted plants that had been fertilized with organic material known as compost. The presence of H. capsulatum in the original compost was detected using the dot-enzyme-linked immunosorbent assay. Nested-PCR, using a specific protein Hcp100 coding gene sequence, confirmed the fungal identification associated with an unusual histoplasmosis outbreak in Acapulco. Although, diversity between the H. capsulatum isolate from the hotel and some clinical isolates from Guerrero (positive controls) was observed using random amplification of polymorphic DNA based-PCR, sequence analyses of H-anti and ole fragment genes revealed a high homology (92-99%) between them.     

Improvement of <Emphasis Type="Italic">Escherichia coli</Emphasis> production strains by modification of the phosphoenolpyruvate:sugar phosphotransferase system

The application of metabolic engineering in Escherichia coli has resulted in the generation of strains with the capacity to produce metabolites of commercial interest. Biotechnological processes with these engineered strains frequently employ culture media containing glucose as the carbon and energy source. In E. coli, the phosphoenolpyruvate:sugar phosphotransferase system (PTS) transports glucose when this sugar is present at concentrations like those used in production fermentations. This protein system is involved in phosphoenolpyruvate-dependent sugar transport, therefore, its activity has an important impact on carbon flux distribution in the phosphoenolpyruvate and pyruvate nodes. Furthermore, PTS has a very important role in carbon catabolite repression. The properties of PTS impose metabolic and regulatory constraints that can hinder strain productivity. For this reason, PTS has been a target for modification with the purpose of strain improvement. In this review, PTS characteristics most relevant to strain performance and the different strategies of PTS modification for strain improvement are discussed. Functional replacement of PTS by alternative phosphoenolpyruvate-independent uptake and phosphorylation activities has resulted in significant improvements in product yield from glucose and productivity for several classes of metabolites. In addition, inactivation of PTS components has been applied successfully as a strategy to abolish carbon catabolite repression, resulting in E. coli strains that use more efficiently sugar mixtures, such as those obtained from lignocellulosic hydrolysates.