Sexual regeneration on a tropical inselberg in French Guiana: an inselberg specialist versus a species with a wider ecological amplitude

This study compares sexual regeneration of two species of Clusia L. (Clusiaceae). The two woody perennials co-occur on a neotropical inselberg in French Guiana. I studied whether the two congeners, which differ in ecological amplitudes, also differ in effectiveness of sexual regeneration and survival strategies, as suggested by previous evidence from different ecosystems. Animal dispersal, secondary removal, germination, seedling mortality and juvenile distribution were examined in an inselberg specialist (Clusia blattophila) and a species with a broader ecological amplitude (Clusia nemorosa). Habitat heterogeneity was accounted for. The two species differed in parameters of individual recruitment stages such as preservation of seed germinability, seedling mortality and juvenile distribution. C. blattophila, the inselberg specialist, suffered high losses during the whole recruitment process and had low juvenile density in spite of its large cover and dominance in the shrub patches. Survival is effected by individual persistence and supported by extensive vegetative growth. C. nemorosa has inefficient primary dispersal and high seedling mortality, but exhibits higher germination rate, higher preservation of seed germinability and numerous juveniles in the community. This suggests that sexual reproduction is important for C. nemorosa, but the ability to reproduce is limited due to the ecosystem characteristics. Microhabitat heterogeneity affected most recruitment stages, but the most suitable sites were not concordant across the recruitment stages. The highest juvenile density of both species occurred in shrub patches. From the long-term perspective of both species, this results in a limited ability to colonize open microhabitats, which may limit succession towards the edaphic climax.     

Can juvenogens,biochemically targeted hormonogen compounds,assist in environmentally safe insect pest management?

Two different types of juvenogens, biochemically targeted hormonogen compounds were tested for their potency to act as insect pest management agents. In the performed biological screening, wax-like esteric juvenogens (3-10) proved to be convenient agents for controlling blowfly and termites, and displayed species selectivity: cis-N-{2-[4-(2-butanoyloxycyclohexyl)methyl]phenoxy}ethyl carbamate (3) was highly active on blowfly (Neobellieria bullata), while trans-N-{2-[4-(2-hexadecanoyloxycyclohexyl)methyl]-phenoxy}ethyl carbamate (6) showed high activity on termite (Prorhinotermes simplex). Glycosidic juvenogens, isomeric N-{2-{4-{[2-(beta-D-galactopyranosyloxy)cyclohexyl]methyl}phenoxy}ethyl carbamates (13 and 14), were proved to act as systemic agents, suitable for protecting plants against phytophagous insects (e.g. aphids). Due to the prolonged action of juvenogens, which is connected with the sequential liberating of the biologically active molecule of the insect juvenile hormone bioanalog from the juvenogen molecule by means of enzymic systems of target insects and/or their host plants, more insect individuals can be treated by juvenogens, which are species-targeted structures due to their different physicochemical properties. The results achieved with both types of juvenogens were promising, concerning their final effect on the tested insect species, and the compounds 3-6, 9 (cis-(9Z)-N-{2-[4-(2-(octadec-9-enoyl)oxycyclohexyl)methyl]phenoxy}ethyl carbamate), 13 and 14 proved to represent convenient insect pest management agents for potential practical applications against different insect pests.     

Contrasting Effect of Prepulse Signals on Performance of Toxoplasma-Infected and Toxoplasma-Free Subjects in an Acoustic Reaction Times Test

Background

About 30% of people on Earth have latent toxoplasmosis. Infected subjects do not express any clinical symptoms, however, they carry dormant stages of parasite Toxoplasma for the rest of their life. This form of toxoplasmosis is mostly considered harmless, however, recent studies showed its specific effects on physiology, behaviour and its associations with various diseases, including psychiatric disorders such as schizophrenia. Individuals who suffer from schizophrenia have about 2.7 times higher prevalence of Toxoplasma-seropositivity than controls, which suggests that some traits characteristic of schizophrenic patients, including the sex difference in schizophrenia onset, decrease of grey matter density in specific brain areas and modification of prepulse inhibition of startle reaction could in fact be caused by toxoplasmosis for those patients who are Toxoplasma-seropositive.

Methodology/Principal Findings

We measured the effect of prepulse inhibition/facilitation of the startle reaction on reaction times. The students, 170 women and 66 men, were asked to react as quickly as possible to a startling acoustic signal by pressing a computer mouse button. Some of the startling signals were without the prepulse, some were 20 msec. preceded by a short (20 msec.) prepulse signal of lower intensity. Toxoplasma-seropositive subjects had longer reaction times than the controls. Acoustic prepulse shorted the reaction times in all subjects. This effect of prepulse on reaction times was stronger in male subjects and increased with the duration of infection, suggesting that it represented a cumulative effect of latent toxoplasmosis, rather than a fading out after effect of past acute toxoplasmosis.

Conclusions

Different sensitivity of Toxoplasma-seropositive and Toxoplasma-seronegative subjects on effect of prepulses on reaction times (the toxoplasmosis-prepulse interaction) suggested, but of course did not prove, that the alternations of prepulse inhibition of startle reaction observed in schizophrenia patients probably joined the list of schizophrenia symptoms that are in fact caused by latent toxoplasmosis.     

Disjunct Occurrences of Plant Species in the Refugial Mires of Bulgaria

Many mire vascular plant and bryophyte species have disjunct occurrences in Bulgaria despite that most of south-eastern Europe is not suitable for the occurrence of permanently waterlogged and nutrient-limited wetlands due to the current and glacial dry climate conditions as well as prevailing limestone bedrock. Unfortunately, such important distributional data are scattered throughout numerous papers and reports, and are not adequately provided even by national checklists and floras. No attempt to summarize them has been done yet. Therefore, the main aim of this paper is to review and enlarge such data, and to use the resulting data set to address the question whether the disjunctly occurring rare species are concentrated in certain mire complexes or even in particular vegetation plots and if they do characterize such localities. Our current research shows that the phenomenon of isolated occurrences of mire plants in Bulgaria is even more widespread than previously thought. Seventeen species were found as new for Bulgaria with their distribution range limits there, and distributional data of many other species, including some previously considered extinct, were enlarged. Fifty-four mire species were found at only three or fewer sites. Our analyses showed a conspicuous concentration of rare, disjunctly occurring species at a few sites, which are, however, largely unexplored in terms of palaeoecology or ecology, not legally protected and currently threatened by human activities. The distributions of target rare species within Bulgarian mires were significantly nested, which means that more species-poor assemblages were subsets of richer ones. Nestedness was significantly related to the estimated area of mire complex, but not all high-diversity mires were large. Disjunctly occurring rare species were more concentrated in particular vegetation plots at lower altitudes and in mineral-rich fens. Fragmentary data about the ecology and history of Bulgarian refugial mires suggest that these mires harbour specific ecotypes and genotypes, contain specifically distributed biogeographic groups of species, provide an opportunity to test biogeographical hypotheses and shelter crucial information about the history of European mires. Thus, these sites have a potential to become a source of very important information for biogeographical, palaeoecological, and phylogeographical analyses.     

Elevated TCA cycle function in the pathology of diet-induced hepatic insulin resistance and fatty liver

The manner in which insulin resistance impinges on hepatic mitochondrial function is complex. Although liver insulin resistance is associated with respiratory dysfunction, the effect on fat oxidation remains controversial, and biosynthetic pathways that traverse mitochondria are actually increased. The tricarboxylic acid (TCA) cycle is the site of terminal fat oxidation, chief source of electrons for respiration, and a metabolic progenitor of gluconeogenesis. Therefore, we tested whether insulin resistance promotes hepatic TCA cycle flux in mice progressing to insulin resistance and fatty liver on a high-fat diet (HFD) for 32 weeks using standard biomolecular and in vivo (2)H/(13)C tracer methods. Relative mitochondrial content increased, but respiratory efficiency declined by 32 weeks of HFD. Fasting ketogenesis became unresponsive to feeding or insulin clamp, indicating blunted but constitutively active mitochondrial β-oxidation. Impaired insulin signaling was marked by elevated in vivo gluconeogenesis and anaplerotic and oxidative TCA cycle flux. The induction of TCA cycle function corresponded to the development of mitochondrial respiratory dysfunction, hepatic oxidative stress, and inflammation. Thus, the hepatic TCA cycle appears to enable mitochondrial dysfunction during insulin resistance by increasing electron deposition into an inefficient respiratory chain prone to reactive oxygen species production and by providing mitochondria-derived substrate for elevated gluconeogenesis.     

Production of biodiesel by Burkholderia cepacia lipase as a function of process parameters

Despite the already established route of chemically catalyzed transesterification reaction in biodiesel production, due to some of its shortcomings, biocatalysts such as lipases present a vital alternative. Namely, it was noticed that one of the key shortcomings for the optimization of the enzyme catalyzed biodiesel synthesis process is the information on the lipase activity in the reaction mixture. In addition to making optimization difficult, it also makes it impossible to compare the results of the independent research. This article shows how lipase intended for use in biodiesel synthesis can be easily and accurately characterized and what is the enzyme concentration that enables achievement of the desired level of fatty acid methyl esters (FAME) in the final product mixture. Therefore, this study investigated the effect of two different activity loads of Burkholderia cepacia lipase on the biodiesel synthesis varying the pH and temperature optimal for lipase activity. The optimal lipase pH and temperature were determined by two different enzyme assays: spectrophotometric and titrimetric. The B. cepacia lipase pH optimum differentiated between assays, while the lipase optimally hydrolyzed substrates at 50°C. The analysis of FAME during 24 hr of biodiesel synthesis, at two different enzyme concentrations, pH 7, 8, and 10, and using two different buffers, revealed that the transesterification reaction at optimal pH, 1 hr reaction time and lipase activity load of 250 U per gram of reaction mixture was sufficient to produce more than 99% FAME.     

NTRS, a new family of highly repetitive DNAs specific for the T1 chromosome of tobacco

Species-specific repeated DNAs are important for identifying genomic components of hybrid organisms in plant breeding and in taxonomic studies, and we have previously described the HRS60 and GRS families of highly repetitive DNA sequences in tobacco. Here we describe a new family of highly repetitive DNA sequences termed NTRS (SspI family) that we have isolated from Nicotiana tomentosiformis (Goodspeed) and characterized and that is specific for the genomes of several species of the subgenus Tabacum. In situ hybridization showed that NTRS sequences are present in three pairs of chromosomes of N. tomentosiformis, six pairs of chromosomes of N. kawakamii, and only one pair of chromosomes of N. tabacum at an intercalary site. The NTRS family is not present in the N. otophora genome. The majority of NTRS sequences appeared to be organized in tandem arrays in which local DNA structures sensitive to single strand-specific chemical probes, potassium permanganate, and osmium tetroxide complexed with pyridine revealed a periodicity of 220 bp, equal to the length of the repeat unit. The inner cytosine in CCGG and CC(A/T)GG sequences of the NTRS family is frequently methylated. Cloned and sequenced NTRS monomeric units are 212–219 bp in length and show 83.5%–95% mutual homology. They exhibit properties characteristic for molecules that possess stable intrinsic curvature, but there are differences among individual monomers in the degree of curvature. NTRS sequences like HRS60 and GRS sequences, were found to specify nucleosome positions. Received: 12 November 1996 / in revised form: 12 May 1997 / Accepted: 12 May 1997     

Genetic and Biochemical Characterization of Mutants of Bacillus subtilis Defective in Succinate Dehydrogenase

Eleven succinate-accumulating mutants of Bacillus subtilis have been mapped by transformation and transduction crosses and characterized with respect to activities of citric acid cycle enzymes. These mutants could be divided into three genetic groups. Nine of the mutants were found to map between argA and leu in the citF locus. A second group was located between lys-1 and trpC2 and the third group could not be located on the B. subtilis chromosome in extensive transduction crosses. All of the citF mutants lack detectable succinate dehydrogenase activity, whereas both of the other groups show a reduced level of this enzyme. In addition, most of the mutants in the citF locus lack cytochrome a, whereas the level of this cytochrome is normal in the other two groups. A procedure has been devised for the solubilization of the succinate dehydrogenase from the membrane of B. subtilis with the non-ionic detergent Brij 58. Some properties of the soluble and bound forms of succinate dehydrogenase are described.