Antimicrobial activity of saponin fractions of the leaves of Gymnema sylvestre and Eclipta prostrata

The antimicrobial activity of saponin fractions from the leaves of Gymnema sylvestre and Eclipta prostrata was evaluated against pathogenic bacteria and fungi in an in vitro condition. A series of concentrations of crude and pure saponin fractions were tested for antimicrobial activity by zone of inhibition method. The pure saponin fractions were found to be more effective against tested bacterial pathogens when compared to crude saponin fractions. The minimum inhibitory concentration (MIC) exhibited by the pure saponin fraction of G. sylvestre was found to be in the range of 600–1,200 mg/l against bacterial strains and 1,400 mg/l for fungal isolates. In the case of E. prostrata, the range was 1,000–1,200 mg/l for bacteria and 1,400 mg/l for fungal isolates. The susceptibility of bacterial pathogens for saponin fractions was in the order of P. aeruginosa, E. coli, S. typhi, K. pneumoniae, P. mirablis, S. aureus and for fungal pathogens A. fumigatus followed by A. niger and A. flavus. Whereas, A. niger was more susceptible to inhibition by E. prostrata saponin fractions, followed by A. flavus and A. fumigatus. The antimicrobial potential of saponin fractions was compared with antibiotics, Chloramphenicol and Amphotericin-B with respect to bacteria and fungi. The present study suggests that the saponin fractions G. sylvestre and E. prostrata possess significant antibacterial and antifungal activity. Our results further suggest that saponins of G. sylvestre and E. prostrata can be used as a potential fungicide against pathogenic fungi.     

Pointwise testing with functional data using the Westfall-Young randomization method

We consider hypothesis testing with smooth functional data byperforming pointwise tests and applying a multiple comparisonsprocedure. Methods based on general inequalities, such as Bonferroni’smethod, do not perform well because of the high correlationbetween observations at nearby points. We consider the multiplecomparison procedure proposed by Westfall & Young (1993)and show that it approximates a multiple comparison correctionfor a continuum of comparisons as the grid for pointwise comparisonsbecomes finer. Simulations and an application verify that thisresult applies in practical settings.     

The Benjamini-Hochberg method with infinitely many contrasts in linear models

Benjamini and Hochberg's method for controlling the false discoveryrate is applied to the problem of testing infinitely many contrastsin linear models. Exact, easily calculated critical values arederived, defining a new multiple comparisons method for testingcontrasts in linear models. The method is adaptive, dependingon the data through the F-statistic, like the Waller–DuncanBayesian multiple comparisons method. Comparisons with Scheffé'smethod are given, and the method is extended to the simultaneousconfidence intervals of Benjamini and Yekutieli.     

A note on controlling the number of false positives

Summary :   Lehmann and Romano (2005, Annals of Statistics 33, 1138–1154) discuss a Bonferroni-type procedure that bounds the probability that the number of false positives is larger than a specified number. We note that this procedure will have poor power as compared to a multivariate permutation test type procedure when the experimental design accommodates a permutation test. An example is given involving gene expression microarray data of breast cancer tumors.     

The effects of fire, local environment and time on ant assemblages in fens and forests

We investigated the effects of the abiotic environment, plant community composition and disturbance by fire on ant assemblages in two distinct habitat types in the Siskiyou Mountains in northern California and southern Oregon, USA. Sampling over 2 years in burned and unburned Darlingtonia fens and their adjacent upland forests, we found that the effects of disturbance by fire depended on habitat type. In forests, fire intensity predicted richness in ant assemblages in both years after the fire, and plant community composition predicted richness 2 years after the fire. No factors were associated with richness in the species‐poor fen ant assemblages. Species‐specific responses to both habitat type and disturbance by fire were idiosyncratic. Assemblage composition depended on habitat type, but not disturbance by fire, and the composition of each assemblage between years was more dissimilar in burned than unburned sites.     

Translating host-specificity test results into the real world: The need to harmonize the yin and yang of current testing procedures

In its modern era, the discipline of biological control can be perceived as being subject to a series of tensions due to differences in philosophy, different needs, and different practices; these include the view that biological control is environmentally friendly and desirable vs. the view that any organism alien to a particular habitat should be considered an undesirable invasive, the need to protect nontarget species vs. the need to introduce the most effective biological control agents and the need to know what an agent might attack under normal field conditions vs. the restrictive nature of current testing procedures. These tensions are particularly manifest in the area of host-specificity testing where researchers interact most directly with regulators and policy-makers and recent “incidents” of nontarget use by biological control agents in three regions have brought them to the fore. The empirical tension between needing more certainty about agent host-range in the real world and being obliged to test this primarily under highly restricted conditions is of most concern to researchers. This paper suggests ways to reduce this through improvements in (1) what plants are tested, (2) how the selected plants are tested, and (3) how the test data are interpreted and communicated to regulators. It is argued that the currently used centrifugal phylogenetic method for selecting test plant lists should be modernized to accommodate the many recent improvements in knowledge of plant phylogenetic relationships and insect host-choice evolution and behavior. The reliance on quarantine-based testing is briefly examined and low- and high-technology alternatives considered. Both these are rejected, at least in the short-term, as being impractical, and the use is proposed of comparative laboratory-based vs. open-field host tests against a few key nontarget species to proactively calibrate subsequent quarantine data and aid interpretation of results obtained under artificial conditions. While these improvements should help better translate host-test results to real-world outcomes, it is essential that there be increased transparency in the communication of these results to regulators, with discussions of different components of risk, such as localized vs. widespread and short-term collateral damage vs. long-term evolutionary impact. Harmonizing the tensions that currently impinge on biological control can only be achieved through improving the quality of information provided, which will help regulators make decisions that are based more on knowledge and less on the often ill-perceived fears of the public.     

Rapid preliminary characterisation of host specificity of leaf-beetles (Coleoptera: Chrysomelidae)

Rapid characterisation of host specificity is important both in biological control of weeds and studies in ecology and evolution. A means for doing this was developed and tested on four species of leaf beetles of interest for biological control of the weed Mimosa pigra (Mimosaceae). We identified the most promising for the more detailed tests necessary to obtain release approval. The impact of time-dependent effects and effects of experience were also investigated as part of this study but were not detected. Short-term host specificity tests on adult feeding accurately predicted the results of longer term trials. The long-term trial showed that survival on a plant species depended on feeding on it. Hence short-term feeding trials can predict the longer term survival of adults on other plant species. Different feeding results were obtained in cut foliage versus entire plants but no consistent pattern was shown: of the two insect species tested, one species ate more of the cut material while the opposite was demonstrated for the second species. Species in order of priority for further consideration as biocontrol agents were Syphrea bibiana, Genaphthona sp., Syphrea sp. and Paria sp. The latter three species were probably not sufficiently specific for release. The tests done here allow the identification of the most likely species upon which to conduct the more laborious and difficult larval developmental tests, saving considerable resources.     

Comparison of surface electromyography and myotonometric measurements during voluntary isometric contractions

Objectives: Muscle stiffness increases during muscle contraction. The purpose of this study was to determine the strength of the correlation between myotonometric measurements of muscle stiffness and surface electromyography (sEMG) measurements during various levels of voluntary isometric contractions of the biceps brachii muscle. Subjects: Eight subjects (four female; four male), with mean age of 30.6±8.23 years, volunteered to participate in this study. Methods: Myotonometer and sEMG measurements were taken simultaneously from the right biceps brachii muscle. Data were obtained: (1) at rest, (2) while the subject held a 15 lb (6.8 kg) weight isometrically and, (3) during a maximal voluntary isometric contraction. Myotonometer force–displacement curves (amount of tissue displacement to a given unit of force applied perpendicular to the muscle) were compared with sEMG measurements using Pearson’s product–moment correlation coefficients. Results: Myotonometer and sEMG measurement correlations ranged from −0.70 to −0.90. The strongest correlations to sEMG were from Myotonometer force measurements between 1.00 and 2.00 kg. Conclusions: Myotonometer and sEMG measurements were highly correlated. Tissue stiffness, as measured by the Myotonometer, appears capable of assessing changes in muscle activation levels.     

Mapping of quantitative trait loci controlling adaptive traits in coastal Douglas-fir. II. Spring and fall cold-hardiness

Quantitative trait loci (QTLs) affecting fall and spring cold-hardiness were identified in a three-generation outbred pedigree of coastal Douglas-fir [Pseudotsuga meniziesii (Mirb.) Franco var. menziesii]. Eleven QTLs controlling fall cold-hardiness were detected on four linkage groups, and 15 QTLs controlling spring cold-hardiness were detected on four linkage groups. Only one linkage group contained QTLs for both spring and fall cold-hardiness, and these QTLs tended to map in close proximity to one another. Several QTLs were associated with hardiness in all three shoot tissues assayed in the spring, supporting previous reports that there is synchronization of plant tissues during de-acclimatization. For fall cold-hardiness, co-location of QTLs was not observed for the different tissues assayed, which is consistent with previous reports of less synchronization of hardening in the fall. In several cases, QTLs for spring or fall cold-hardiness mapped to the same location as QTLs controlling spring bud flush. QTL estimations, relative magnitudes of heritabilities, and genetic correlations based on clonal data in this single full-sib family, supports conclusions about the genetic control and relationships among cold-hardiness traits observed in population samples of Douglas-fir in previous studies. Received: 20 July 2000 / Accepted: 19 October 2000     

Seed bank spatial pattern in a temperate secondary forest

Abstract. Seed bank spatial pattern was studied in a secondary forest dominated by Fagus sylvatica and Betula celtiberica in the Urkiola Natural Park (N Spain). Soil samples were taken every 2 m in a regular grid (196 points) and divided into two fractions (0–3 cm and 3–10 cm deep). The viable seed bank was studied by monitoring seedling emergence for ten months. The effect of different factors on seed bank composition and patterning was analysed using constrained ordination as a hypothesis testing tool. Furthermore, the existence of spatial autocorrelation was evaluated by geostatistical analysis. Seed density was high, 7057 seed.m^?2, with a few species dominating. Species composition in the various layers were significantly correlated. The seed bank showed significant spatial structure, which was partially explainable by the spatial structure of the canopy and understorey vegetation. Spatial clumping from 0–8 m was observed in seed bank density and composition, mainly due to the pattern of two abundant taxa Juncus effusus and Ericaceae. The Ericaceae seed bank was related to the spatial distribution of dead stumps of Erica arborea. J. effusus was not present in the above‐ground vegetation, which indicates that its seed bank was formed in the past. As expected, the seed bank of this forest reflects its history, which is characterized by complex man‐induced perturbations. The seed bank appears to be structured as a consequence of contrasting driving forces such as canopy structure, understorey composition and structural and microhabitat features.