Large Scale Relationship between Aquatic Insect Traits and Climate

Climate is the predominant environmental driver of freshwater assemblage pattern on large spatial scales, and traits of freshwater organisms have shown considerable potential to identify impacts of climate change. Although several studies suggest traits that may indicate vulnerability to climate change, the empirical relationship between freshwater assemblage trait composition and climate has been rarely examined on large scales. We compared the responses of the assumed climate-associated traits from six grouping features to 35 bioclimatic indices (~18 km resolution) for five insect orders (Diptera, Ephemeroptera, Odonata, Plecoptera and Trichoptera), evaluated their potential for changing distribution pattern under future climate change and identified the most influential bioclimatic indices. The data comprised 782 species and 395 genera sampled in 4,752 stream sites during 2006 and 2007 in Germany (~357,000 km^² spatial extent). We quantified the variability and spatial autocorrelation in the traits and orders that are associated with the combined and individual bioclimatic indices. Traits of temperature preference grouping feature that are the products of several other underlying climate-associated traits, and the insect order Ephemeroptera exhibited the strongest response to the bioclimatic indices as well as the highest potential for changing distribution pattern. Regarding individual traits, insects in general and ephemeropterans preferring very cold temperature showed the highest response, and the insects preferring cold and trichopterans preferring moderate temperature showed the highest potential for changing distribution. We showed that the seasonal radiation and moisture are the most influential bioclimatic aspects, and thus changes in these aspects may affect the most responsive traits and orders and drive a change in their spatial distribution pattern. Our findings support the development of trait-based metrics to predict and detect climate-related changes of freshwater assemblages.     

Photoelectrochemistry of dyes in phospholipid liposome.

The systems consisting of phenosafranin or thionine dye in the presence of phospholipid liposome in aqueous solution generate photovoltage when studied in a photoelectrochemical cell. A possible mechanism of photovoltage generation suggests the photoinduced electron transfer from phospholipid to dye in liposome through charge-transfer (CT) interaction. In these dye-phospholipid systems, a good correlation between the photovoltage (Voc) determined by photoelectrochemical studies and the equilibrium constant (Kc) determined by spectrophotometric studies, confirms the mechanism.     

Chemotherapeutic potential of 9-phenyl acridine: biophysical studies on its binding to DNA

Acridines and their derivatives are well-known probes for nucleic acids as well as being relevant in the field of drug development to establish new chemotherapeutic agents. We have shown from molecular modelling studies that 9-phenyl acridine and some of its derivatives can act as inhibitors of topoisomerase I and thus have potential to act as anticancer agents. Rational design of new compounds for therapeutics requires knowledge about their structural stability and interactions with various cellular macromolecules. In this regard it is important to know how these molecules would interact with DNA. Here we report the interaction of 9-phenyl acridine (ACPH) with calf thymus DNA (CT-DNA) based on various biophysical and molecular modelling studies. Spectrophotometric studies indicated that ACPH binds to CT-DNA. DNA melting studies revealed that binding of ACPH to CT-DNA resulted in a small increase in melting temperature, which is unlikely in case of classical intercalator; rather, it indicates external binding. Viscosity measurements show that ACPH exhibits groove binding. Competitive binding of ACPH to CT-DNA pre-bound to ethidium bromide (EB) showed slow quenching. Measurement of the binding constant of ACPH by fluorescent intercalator displacement (FID) assay corroborated the notion that there was groove binding. Molecular modelling studies also supported this finding. Results indicate that binding of ACPH is through partial intercalation in the minor groove of DNA.     

Purification and partial characterization ofd-(−)-lactate dehydrogenase fromLactobacillus helveticus CNRZ 32

Summary d-(–)-Lactate dehydrogenase (LDH) was purified to homogeneity from a cell-free extract ofLactobacillus helveticus CNRZ 32. The native enzyme was determined to have a molecular weight of 152 000 and consisted of four identical subunits of 38 000. This enzyme was NAD dependent fructose 1,6-diphosphate (FDP) and ATP independent. It was most active on pyruvate followed by -hydroxypyruvate as substrates. TheK _m values for pyruvate andd-(–)-lactate were 0.64 and 68.42 mM respectively, indicating that the enzyme has a higher affinity for pyruvate. The enzyme activity was completely inhibited byp-chloromercuribenzoate (1 mM) and partially by iodoacetate, suggesting the involvement of the sulfhydryl group (-SH) in catalysis. Optima for activity by the purified enzyme were pH 4.0 and 50–60°C. Limited inhibition ofd-(–)-LDH was observed with several divalent cations. Additionally, HgCl₂ was observed to strongly inhibit enzyme activity. The purified enzyme was not affected by dithiothreitol or any of the metal chelating agents examined.     

Cloning of peptidase genes from Lactobacillus helveticus CNRZ 32

Lactic acid bacteria express a complex proteolytic enzyme system that is capable of hydrolyzing casein to amino acids. We have begun to examine the number and specificity of exopeptidases from Lactobacillus helveticus CNRZ 32. A genomic library of L. helveticus CNRZ 32 DNA fragments from a Sau3A partial digestion was constructed in Escherichia coli DH5 utilizing pJDC9. This library was screened for the presence of aminopeptidase, X-prolyl dipeptidyl aminopeptidase (X-PDAP), and dipeptidase activities by two methods. The first screening identified an aminopeptidase II (APII) and X-PDAP. The X-PDAP was determined to be present on four independent DNA inserts ranging in size from 3.5 to 7.7 kilobase pairs (kbp). EcoRI/EcoRV digests of these plasmids suggested that all inserts had 1.0 and 1.8 kbp fragments in common. The gene for APII was determined to be present on three independent DNA inserts ranging in size from 8.2 to 11.3 kbp. EcoRI digestion of these plasmids indicated that 1.2 and 1.8 kbp fragments were in common. The second screening identified an additional aminopeptidase (API), a di/tripeptidase (DTP) with prolinase activity, a broad-specificity dipeptidase (DPI), and a narrow-specificity dipeptidase (DPII). The insert size of clones expressing API, DTP, DPI, DPII were 4.8, 9.5, 5.8, and 6.3 kbp, respectively. Histochemical staining of native polyacrylamide gels from recombinant E. coli cultures demonstrated that the cloned peptidase co-migrated with native L. helveticus CNRZ 32 enzymes. Correspondence to: J. L. Steele     

Pathognomonic macular ripples are revealed by polarized infrared retinal imaging

A pathognomonic macular ripple sign has been reported with scanning laser ophthalmoscopy images in patients with foveal hypoplasia, though the optical basis of this sign is presently unknown. Here we present a case series of seven individuals with foveal hypoplasia (based on spectral domain optical coherence tomography). Each patient underwent infrared scanning laser ophthalmoscopy retinal imaging in both eyes, acquired with and without a polarization filter and assessment for a ripple-like effect in the fovea. On imaging, macular ripples were present in all eyes with foveal hypoplasia when using a polarization filter, but not when imaged without the filter. We conclude that the macular ripple sign is an imaging artifact attributable to the unique pattern of phase retardation of the Henle fiber layer in the setting of foveal hypoplasia. By utilizing a polarization filter with retinal photography, this feature can be exploited to promptly identify foveal hypoplasia in settings where OCT is not possible due to nystagmus.     

Inhibition of Pigment Biosynthesis in Cucumber Cotyledons by Isoxaflutole

Isoxaflutole [5-cyclopropyl-4-(2-methylsulphonyl-4-trifluromethylbenzoyl)isoxazole] is a new preemergence herbicide for broad-spectrum weed control in maize. The effect of isoxaflutole on chlorophyll (Chl) and carotenoid (Car) biosynthesis was investigated in cucumber (Cucumis sativus L.) cotyledons. Etiolated tissue was incubated with 5 mM isoxaflutole for 24 h and irradiated (60 mol m^-2 s^-1). The irradiation for 3 h did not reduce Chl a, Chl b, and Car contents, but after a 28-h irradiation the contents of Chl a and Car decreased by 35 and 15 %, respectively, and the content of Chl b increased by 24 %. Increasing the concentration of isoxaflutole beyond 5 mM resulted in reduction of Chl a (71 %), Chl b (20 %), and Car (31 %) contents. Similarly, increase in irradiance from 60 to 180 mol m^-2 s^-1 resulted in larger reduction of Chl and Car contents. Exogenously supplied 5-aminolevulinic acid did not reverse the isoxaflutole-inhibited Chl synthesis, whereas an exogenously supplied homogentisic acid lactone reversed the inhibition of pigment synthesis due to isoxaflutole.     

Identification of a novel locus that regulates expression of toxin genes in Clostridium perfringens

A novel gene that regulates the alpha-toxin (plc), kappa-toxin (colA), and theta;-toxin (pfoA) genes was identified using toxin-negative mutant strains of Clostridium perfringens. The cloned 3.2-kb fragment contained the virX gene encoding a 51-amino acid polypeptide of unknown function that seemed to be responsible for the activation of toxin genes. The virX knock out mutant of wild-type strain 13 showed a reduced expression of the plc, colA, and pfoA genes, which was complemented by the transformation of the intact virX gene. Deletion and site-directed mutagenesis studies suggested that the virX gene acts as a regulatory RNA rather than as a peptide regulator. The virX locus found in this study might play a part in the signal transduction to regulate toxin production in C. perfringens.