RNA kink turns to the left and to the right

A helix-loop-helix within the group I intron has most of the canonical sequence elements of a kink turn (K-turn), yet it bends in the opposite direction. The reverse K-turn kinks toward the major rather than the minor grooves of the flanking helices. This suggests that there are two distinct subclasses of tertiary structures that a K-turn secondary structure can adopt. The final structure may be specified by external factors, such as protein binding or the tertiary structural context, rather than the intrinsic conformation of the RNA.     

Transport and release of chemicals from plastics to the environment and to wildlife

Plastics debris in the marine environment, including resin pellets, fragments and microscopic plastic fragments, contain organic contaminants, including polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons, petroleum hydrocarbons, organochlorine pesticides (2,2′-bis(p-chlorophenyl)-1,1,1-trichloroethane, hexachlorinated hexanes), polybrominated diphenylethers, alkylphenols and bisphenol A, at concentrations from sub ng g^–1 to µg g^–1. Some of these compounds are added during plastics manufacture, while others adsorb from the surrounding seawater. Concentrations of hydrophobic contaminants adsorbed on plastics showed distinct spatial variations reflecting global pollution patterns. Model calculations and experimental observations consistently show that polyethylene accumulates more organic contaminants than other plastics such as polypropylene and polyvinyl chloride. Both a mathematical model using equilibrium partitioning and experimental data have demonstrated the transfer of contaminants from plastic to organisms. A feeding experiment indicated that PCBs could transfer from contaminated plastics to streaked shearwater chicks. Plasticizers, other plastics additives and constitutional monomers also present potential threats in terrestrial environments because they can leach from waste disposal sites into groundwater and/or surface waters. Leaching and degradation of plasticizers and polymers are complex phenomena dependent on environmental conditions in the landfill and the chemical properties of each additive. Bisphenol A concentrations in leachates from municipal waste disposal sites in tropical Asia ranged from sub µg l^–1 to mg l^–1 and were correlated with the level of economic development.     

Circadian Rhythm of the Pupillary Response to Morphine and to Naloxone

Mice respond to morphine with characteristic mydriasis which is antagonized by naloxone. The present study presents data on the diurnal variation of these responses. The mydriatic response is at its highest level at 0800 and has a nadir at 2400. This effect is not influenced by ambient light conditions. The miotic response to naloxone in the morphine-dilated pupil is maximal between 1200 and 1600 and minimal at 0400. The curves of the responses to the two drugs, therefore, differ as do their acrophases. Pharmacokinetic factors are probably not responsible for the observed variations. It is speculated that these diurnal changes may reflect cyclic alteration in the affinity of the opiate receptors to agonists and antagonists, respectively, or in the number of available receptors.     

An approach to the synthesis and attachment of scillabiose to steroids

Hellebrin and transvaalin are two naturally occurring saponins with biological activity. In the present paper, we describe a high yielding route to the synthesis and coupling of their shared glycone, scillabiose, to a model steroid. A convergent coupling strategy utilizing a scillabiose-based glycosyl donor was devised for the glycosylation. This convergent approach is appealing due to its high efficiency and simple deprotection procedure and may find further use in total synthesis of naturally occurring saponins and related compounds sharing the same glycone. Due to the widespread occurrence of this glycone in nature, the complete NMR spectroscopic characterization of all compounds prepared herein is provided as reference material. In addition, glycosylations were performed with the monosaccharide constituents of scillabiose, thereby providing a limited series of glycosylated steroids for potential future evaluation of the effects of the glycone on the overall biological activity.     

Extensions to the known range of the whitefin gudgeon to Europe and biogeographical implications

In 1998 and 1999, the whitefin gudgeon Gobio albipinnatus was common in the Rivers Rhine, Elbe and in the Lower Odra.     

Borealin directs recruitment of the CPC to oocyte chromosomes and movement to the microtubules

The chromosomes in the oocytes of many animals appear to promote bipolar spindle assembly. In Drosophila oocytes, spindle assembly requires the chromosome passenger complex (CPC), which consists of INCENP, Borealin, Survivin, and Aurora B. To determine what recruits the CPC to the chromosomes and its role in spindle assembly, we developed a strategy to manipulate the function and localization of INCENP, which is critical for recruiting the Aurora B kinase. We found that an interaction between Borealin and the chromatin is crucial for the recruitment of the CPC to the chromosomes and is sufficient to build kinetochores and recruit spindle microtubules. HP1 colocalizes with the CPC on the chromosomes and together they move to the spindle microtubules. We propose that the Borealin interaction with HP1 promotes the movement of the CPC from the chromosomes to the microtubules. In addition, within the central spindle, rather than at the centromeres, the CPC and HP1 are required for homologous chromosome bi-orientation.     

Protective and adaptive reactions of the air-conducting and respiratory portions of the lungs to exposure to atmospheric pollutants

A complex structural-functional investigation of protective-adaptive reactions of various parts in the lungs has been performed under inhalation of some toxic substances. To a continuous inhalation effect of 1,2-dichlorpropane, 132 non-inbred white rats have been subjected. At the first stage of the investigation, using specific loading tests, periods for formation of increased and decreased resistivity of the experimental animals have been defined. Under the given scheme of the experiment the state of a maximal resistivity develops by the 30th day of the influence, then it gradually decreases and in 60 days becomes significantly lower than in the control animals. Synchronous changes in resistivity and in loading of the respiratory organs are revealed. The structural-functional investigation of the pneumatic and respiratory parts of the lungs during the period of formation (in 5 days of the influence), at maximum (in 30 days of the influence) and at decreased resistivity (in 60 days of the influence) makes it possible to establish that functional activity of the aero-hematic, aero-epithelial barriers and the surfactant system of the lungs increases during the period of elevated resistivity and decreases at the stage of reduced endurance to the loading. A suggestion is made that, together with other factors, increasing functional activity in the systems studied is an essential component for formation of the elevated stability of the organism against toxic inhalation.