Field study on the foraging characteristics of a ponerine ant,Hagensia havilandi Forel

Summary A field study of the foraging strategy used by the ponerine ant,Hagensia havilandi is reported. They have permanent nests in the leaf litter of coastal forests.H. havilandi is a diurnal forager and collects a variety of live and dead arthropods. These predatory ants exhibit individual foraging with no cooperation in the search for or retrieval of food items. Three colonies were observed and showed similar temporal and spatial foraging patterns. The paths of individual ants were followed and the results showed that the foragers exhibit area fidelity, and return to the nest via a direct route on finding on prey item. Several foragers did not return to the nest at dusk but returned the following morning. Occasionally a limited amount of tandem recruitment was displayed.     

Approximation and characterization of molecular surfaces

The representation and characterization of molecular surfaces are important in many areas of molecular modeling. Parametric representations of protein molecular surfaces are a compact way to describe a surface, and are useful for the evaluation of surface properties such as the normal vector, principal curvatures, and principal curvature directions. Simplified representations of molecular surfaces are useful for efficient rendering and for the display of large-scale surface features. Several techniques for representing surfaces by expansions of spherical harmonic functions have been reported, but these techniques require that the radius function is single valued, that is, each ray from an origin inside the surface intersects the surface at one and only one point. A new technique is described that removes this limitation and can be used to compute surface shape properties. © 1993 John Wiley & Sons, Inc.     

Activity of mushroom polyphenol oxidase in organic medium

A kinetic study of the activity of mushroom polyphenol oxidase in an organic system was carried out to obtain detailed enzyme kinetic data in relation to optimization of reaction conditions and substrate specificity. A simple method for consistent measurement of reaction rates in the heterogeneous enzyme/organic solvent system (consisting of immobilized polyphenol oxidase and a hydrated solution of the substrate in chloroform) was designed. The aqueous content of the system was optimized using p-cresol as the substrate. With this system, a crude extract of Agaricus bisporus was used to hydroxylate and oxidize a range of selected p-substituted phenolic substrates, yielding o-quinone products. Michaelis-Menten kinetics were used to obtain apparent K(M) and V(max) values with respect to each of these substrates. Results from this analysis indicated a correlation between the enzymic kinetic parameters obtained and the steric requirements of the substrates, which could be rationalized in terms of the restricted flexibility of the enzyme when it is in chloroform and also in terms of substrate and solvent hydrophobicity. In the course of the investigation UV molar absorption coefficients of several o-quinones were measured by a novel method: (1)H nuclear magnetic resonance (NMR) spectroscopy was employed to determine component concentrations in reaction mixtures resulting from the transformation of phenols by polyphenol oxidase in chloroform. Thus the UV molar absorption coefficients could be obtained directly, avoiding the necessity to isolate the water-sensitive, unstable o-quinones. (c) 1993 John Wiley & Sons, Inc.     

Potential of fungi as biocontrol agents of polyphagotarsonemus latus (Acari: Tarsonemidae)

Infection of broad mites, Polyphagotarsonemus latus, by conidia of Beauveria bassiana, Hirsutella thompsonii, and Paecilomyces fumosoroseus conidia was investigated in the laboratory under controlled temperature and moisture conditions. Infection of P. latus by the fungus (LC₅₀) was related positively to the 1.16 × 10⁶ B. bassiana conidia per ml, 2.39 × 10³ H. thompsonii conidia per ml, and 1.29 × 10⁵ P. fumosoroseus conidia per ml. Mortality caused by B. bassiana occurred the fastest among densities fluctuating between 65 and 125 mites per leaf. The pathogens B. bassiana and P. fumosoroseus, adjuvants (oil and molasses), and the acaricide ABG6364, a microbial insecticide containing the Beta-exotoxin of Bacillus thuringiensis were evaluated for efficacy against P. latus in a greenhouse test. The B. bassiana treated plants had the greatest and most persistent effect on percentage mortality of total broad mites present per leaf (88 %) followed by the acaricide ABG6364. Use of adjuvants (oil and molasses) did not increase infection of P. latus.     

Rapid changes in oxidative metabolism as a consequence of elicitor treatment of suspension-cultured cells of French bean (Phaseolus vulgaris L.)

Stressed plant cells often show increased oxygen uptake which can manifest itself in the transient production of active oxygen species, the oxidative burst. There is a lack of information on the redox status of cells during the early stages of biotic stress. In this paper we measure oxygen uptake and the levels of redox intermediates NAD/NADH and ATP and show the transient induction of the marker enzyme for redox stress, alcohol dehydrogenase. Rapid changes in the redox potential of elicitor-treated suspension cultures of French bean cells indicate that, paradoxically, during the period of maximum oxygen uptake the levels of ATP and the NADH/NAD ratio fall in a way that indicates the occurrence of stress in oxidative metabolism. This period coincides with the maximum production of active oxygen species particularly H₂O₂. The cells recover and start producing ATP immediately upon the cessation of H₂O₂ production. This indicates that the increased O₂ uptake is primarily incorporated into active O₂ species. A second consequence of these changes is probably a transient compromising of the respiratory status of the cells as indicated in expression of alcohol dehydrogenase. Elicitor-induced bean ADH was purified to homogeneity and the M_r 40 000 polypeptide was subjected to amino acid sequencing. 15% of the whole protein was sequenced from three peptides and was found to have nearly 100% sequence similarity to the amino acid sequence for pea ADH1 (PSADH1). The cDNA coding for the pea enzyme was used to demonstrate the transient induction of ADH mRNA in elicitor-treated bean cells. Enzyme activity levels also increased transiently subsequently. Increased oxygen uptake has previously been thought to be associated with provision of energy for the changes in biosynthesis that occur rapidly after perception of the stress signal. However the present work shows that this rapid increase in oxygen uptake as a consequence of elicitor action is not wholly associated with respiration.     

Land/water ecotone effects in reservoirs on the fish fauna

The morphology and function of one tropical and 25 temperate reservoirs are examined in relation to their effect upon the nature of the land/water interface and, further, to what extent the features of these ecotones satisfy the ecological requirements of the reservoir fish species throughout their life cycle during spawning, larval, juvenile and adult stages. The two main conclusions are that (1) reservoir fish species are especially dependent upon land/water ecotones during their early life history and (2) there exists a strong relationship between the extent of the littoral area and the nature of the fish stocks. Several examples are given to show that manipulation of the land/water ecotone is a major tool for the management of reservoirs advantageously for their major functions.     

Solvation of platinum anti-cancer drugs in methanol-water mixtures

Solubilities and transfer chemical potentials of carboplatin, cisplatin, iproplatin, and several related platinum complexes have been determined in methanol-water mixtures. the range of solvation behaviour is discussed in relation to possible oral administration of complexes of this type.