Potent limonoid insect antifeedant from Melia azedarach

Systematic fractionation of a fruit extract from Argentine Melia azedarach L., which was monitored by an insect antifeedant bioassay, led to the isolation of meliartenin, a limonoid antifeedant, which existed as a mixture of two interchangeable isomers. At 4 microg/cm2 and 1 microg/cm2, the isomeric mixture was as active as azadirachtin in strongly inhibiting the larval feeding of Epilachna paenulata Germ. (Coleoptera: Coccinellidae) and the polyphagous pest, Spodoptera eridania (Lepidoptera: Noctuidae), respectively.     

Evaluation of DNA polymorphisms amplified by arbitrary primers (RAPD) as genetically associated elements to differentiate virulent and non-virulent Paracoccidioides brasiliensis isolates

Randomly amplified polymorphic DNA (RAPD) analysis of 35 Paracoccidioides brasiliensis isolates was carried out to evaluate the correlation of RAPD profiles with the virulence degree or the type of the clinical manifestations of human paracoccidioidomycosis. The dendrogram presented two main groups sharing 64% genetic similarity. Group A included two isolates from patients with chronic paracoccidioidomycosis; group B comprised the following isolates showing 65% similarity: two non-virulent, six attenuated, five virulent, eight from patients with chronic paracoccidioidomycosis and two from patients with acute paracoccidioidomycosis. The virulent Pb18 isolate and six attenuated or non-virulent samples derived from it were genetically indistinguishable (100% of similarity). Thus, in our study, RAPD patterns could not discriminate among 35 P. brasiliensis isolates according to their differences either in the degree of virulence or in the type of the clinical manifestation of this fungal infection.     

Topographical analysis of Schizolobium parahyba chymotrypsin inhibitor (SPCI) by atomic force microscopy

Atomic Force Microscopy (AFM) has been a useful tool for molecular surface analysis and to estimate topographical properties of proteins. Here we report a topographical study of a chymotrypsin inhibitor from Schizolobium parahyba seeds (SPCI) by AFM. The underlying structure of SPCI oligomers has been resolved in nanometer order resolution. SPCI oligomerize in hexagonal, ellipsoid, comet, pyramidal, and "Z" shaped. The hexagonal was the most observed oligomer shape.     

Isolation and partial characterisation of a protein from buck seminal plasma (Capra hircus), homologous to spermadhesins

Spermadhesins are a family of secretory proteins expressed in the male genital tract of pig, horse and bull. Their function and structure have been widely studied, especially those isolated from boar. However, there are no data concerning spermadhesins isolated from buck. Buck seminal plasma was collected and subjected to ion exchange chromatography on DEAE-Sephacel column followed by chromatography in a C18 column coupled to a HPLC system. The purification of the protein was determined by SDS-PAGE and MALDI-TOF analysis exhibiting a molecular mass of 12.5 KDa and showed to be structurally homologous to spermadhesins from boar and stallion.     

A genome-wide strategy for the identification of essential genes in Staphylococcus aureus

To address the need for new approaches to antibiotic drug development, we have identified a large number of essential genes for the bacterial pathogen, Staphylococcus aureus, using a rapid shotgun antisense RNA method. Staphylococcus aureus chromosomal DNA fragments were cloned into a xylose-inducible expression plasmid and transformed into S. aureus. Homology comparisons between 658 S. aureus genes identified in this particular antisense screen and the Mycoplasma genitalium genome, which contains 517 genes in total, yielded 168 conserved genes, many of which appear to be essential in M. genitalium and other bacteria. Examples are presented in which expression of an antisense RNA specifically reduces its cognate mRNA. A cell-based, drug-screening assay is also described, wherein expression of an antisense RNA confers specific sensitivity to compounds targeting that gene product. This approach enables facile assay development for high throughput screening for any essential gene, independent of its biochemical function, thereby greatly facilitating the search for new antibiotics.     

Short-term plasticity at the calyx of held

Synapses show widely varying degrees of short-term facilitation and depression. Several mechanisms have been proposed to underlie short-term plasticity, but the contributions of presynaptic mechanisms have been particularly difficult to study because of the small size of synaptic boutons in the mammalian brain. Here we review the functional properties of the calyx of Held, a giant nerve terminal that has shed new light on the general mechanisms that control short-term plasticity. The calyx of Held has also provided fresh insights into the strategies used by synapses to extend their dynamic range of operation and preserve the timing of sensory stimuli.     

Blend uniformity analysis using stream sampling and near infrared spectroscopy

A near infrared spectroscopic method was developed to determine drug content in a 20% (wt/wt) ibuprofen and spray-dried hydous lactose blend. A blending profile was obtained after blending for 0.5, 1, 3, 5, 10, and 20 minutes. Stream sampling was used to collect about 20 blend samples at each of the blending times from a laboratory scale V-blender. The samples collected were used to develop a near infrared calibration model. The calibration model was then used to determine the drug content of unknown samples from 2 validation blends. The validation blends were not included in the calibration model; they were used to evaluate the effectiveness of the calibration model. A total of 45 samples from the 2 validation blends were predicted by the near infrared calibration model and then analyzed by a validated UV spectrophotometric method. The root mean square error of prediction for the first validation blend was 5.69 mg/g and 3.30 mg/g for the samples from the second blend. A paired t test at the 95% confidence level did not indicate any differences between the drug content predicted by the near infrared spectroscopy (NIRS) method and the validated UV method for the 2 blends. The results show that the NIRS method could be developed while the blending profile is generated and used to thoroughly characterize a new formulation during development by analyzing a large number of samples. The new formulation could be transferred to a manufacturing plant with an NIRS method to facilitate blend uniformity analysis.     

Separation of large circular DNA by electrophoresis in agarose gels

The electrophoresis of circular DNA, ranging in size from 4.4 kilobase pairs (kbp) to 220 kbp, was studied in agarose gels. Bacterial artificial chromosome (BAC) DNA was used as a source of large supercoiled and open circular (relaxed) forms. The open circles above approximately 50 kbp were trapped at the sample wells of 1% agarose gels during electrophoresis at 3 V/cm. Field inversion gel electrophoresis (FIGE) was used to relieve the trapping of the open circles in the gels. Using FIGE (30 s forward pulse time), open circles with sizes of 115 and 220 kbp required reverse pulse times of 3 and 6 s, respectively, to free the circles from open-ended gel fibers. A minimum in the gel velocity of the open circles was measured at approximately 20 kbp. Open circles below approximately 20 kbp migrated slower than the supercoiled forms, and above 20 kbp the order was reversed. These results indicate that when the size of the open circles exceeded the average pore size of a gel and it was forced to span multiple pores, the open circles gained a mobility advantage. Decreasing the ionic strength of the electrophoresis buffer significantly decreased the mobility of the smaller circles and slightly increased the mobility of the larger circles.     

Herpetological diversity along Andean elevational gradients: links with physiological ecology and evolutionary physiology

A well-defined macroecological pattern is the decline in biodiversity with altitude. However, this decline is taxa-specific. For example, amphibians are more diverse than squamates at extreme elevations in the tropical Andes, but this pattern is reversed at extreme elevations in the southern latitudes. Several ecophysiological and evolutionary factors may be related to this difference. At high-elevations in southern latitudes temperature differs dramatically among seasons and dry soils dominate, characteristics that appear to favor lizard physiological ecology. Tropical high altitudes, in contrast, are humid and offer abundant and diverse water resources. These characteristics allow for a richer anuran community but might complicate lizard egg development through temperature and oxygen constrains. Differences in strategies of thermal adaptation might also modulate diversity patterns. The thermal physiology of anurans is extremely labile so that behavioral and physiological performance is maintained despite an altitudinal decrease in field body temperature. Lizards, in contrast, exhibit a conservative thermal physiology and rely on behavioral thermoregulation to face cold and variable temperatures. Both, lizard behavioral strategies and anuran physiological adjustments seem equally efficient in allowing ecological success and diversification for both groups in the tropics up to approximately 3000 m. At higher elevations physiological thermal adaptation is required, and lizards are ecologically constrained, perhaps at various ontogenetic stages. Patterns of biodiversity along environmental clines can be better understood through a physiological approach, and can help to refine and propose hypotheses in evolutionary physiology.     

A cost-effective screening test for detecting AZF microdeletions on the human Y chromosome

PCR-based screening of microdeletions in the azoospermic factor (AZF) on the Yq chromosome is an accepted means of identifying a common genetic cause of male infertility, responsible for 5-15% of cases associated with a low sperm count (相似文献