Anemophilous plants select pollen from their own species from the air

In wind-tunnel experiments, Niklas (1985) has demonstrated the ability of anemophilous plants to select pollen from their own species from the airstream. However, there have been no field experiments to establish whether this operates in nature. We surveyed the pollents on the stigmas of four different, coextensive, dioecious anemophilous species surrounded by a Pinus radiata plantation. The alien pine pollen was overrepresented relative to background levels on only one of the four species. For all three indigenous species with both male and female plants in the area, the highest proportion — in all cases more than 40% — of the pollen found on their stigmas came from their own species. One indigenous species lacked male plants in the area; consequently, the results from this species are difficult to interpret. However, for all four species, there was at least 15% pine pollen, and some pollen of other indigenous species. These results suggest that there is some pollen selection, but that the mechanisms are may be not as effective as Niklas has suggested.     

The anaerobic biodegradation of diethanolamine by a nitrate reducing bacterium

The ability of bacterial cultures to degrade diethanolamine under anoxic conditions with nitrate as an electron acceptor was investigated. A mixed culture capable of anaerobic degradation of diethanolamine was obtained from river sediments by enrichment culture. From this a single bacterial strain was isolated which could use diethanolamine, monoethanolamine, triethanolamine and N-methyl diethanolamine as its sole carbon and energy sources either aerobically or anaerobically. Growth on diethanolamine was faster in the absence of oxygen. The accumulation of possible metabolites in the culture medium was determined as was the ability to grow on certain putative intermediates in the degradation of diethanolamine. A possible pathway for the degradation of ethanolamines by this organism is suggested.     

Genetics of a-agglutunin function in Saccharomyces cerevisiae

The Saccharomyces cerevisiae cell adhesion protein a-agglutinin is composed of an anchorage subunit (Aga1p) and an adhesion subunit (Aga2p). Although functional a-agglutinin is expressed only by a cells, previous results indicated that AGA1 RNA is expressed in both a and α cells after pheromone induction. Expression of the Aga2p adhesion subunit in a cells allowed a-agglutinability, indicating that a cells express the a-agglutinin anchorage subunit, although no role for Aga1p in α cells has been identified. Most of the a-specific agglutination-defective mutants isolated previously were defective in AGA1; a single mutant (La199) was a candidate for an aga2 mutant. Expression of AGA2 under PGK control allowed secretion of active Aga2p from control strains but did not complement the La199 agglutination defect or allow secretion of Aga2p from La 199, suggesting that the La199 mutation might identify a new gene required for a-agglutinin function. However, the La199 agglutination defect showed tight linkage to aga2::URA3 and did not complement aga2::URA3 in a/a diploids. The aga2 gene cloned from La199 was nonfunctional and contained an ochre mutation. The inability of pPGK-AGA2 to express functional Aga2p in La199 was shown to result from an additional mutation(s) that reduces expression of plasmid-borne genes. AGA2 was mapped to the left arm of chromosome VII approximately 28 cM from the centromere.     

Brefeldin a down-regulates the transferrin receptor in K562 cells

The fungal metabolite brefeldin A (BFA) induces profound alterations in the morphology of intracellular organelles. Although BFA promotes the formation of extensive tubular endosomal domains, our understanding of the effects of the antibiotic on vesicle traffic events associated with endocytosis is limited. Thus, alterations in the transferrin (Tf) receptor's endocytic/recycling pathway upon treatment of human erythroleukemia K562 cells with BFA were studied as a pharmacological response. Treatment of K562 cells with BFA caused a down-regulation in the number of cell surface Tf receptors. This effect is highly reminiscent of the well-known action of phorbol 12-myristate 13-acetate (PMA) on Tf receptor traffic in K562 cells. However, our results demonstrate that these two agents down-regulate the Tf receptor via different mechanisms. The effects of BFA and PMA were additive when K562 cells were incubated with both together. Using the In/Sur method, the endocytic rate constant for Tf internalization was determined and PMA was found to greatly enhance k_e, from 0.28 min^–1 to 0.43 min^–1, while BFA had little effect (K_e=0.20 min^–1). In contrast, BFA-treatment alters the exocytic rate constant for return of internalized receptors to the cell surface, with the largest effect exerted on a slow-release, monensin-sensitive, compartment. The sum of the endocytic and exocytic kinetic data support a model in which BFA and PMA down-regulate the Tf receptor in K562 cells by mechanistically distinct actions, with BFA targeting exocytic monensin-sensitive intracellular compartments and PMA acting to exert a profound influence on elements of receptor internalization.Abbreviations BFA brefeldin A - ARF ADP-ribosylation factor - HRP horseradish peroxidase - Tf transferrin - PMA phorbol 12-myristate 13-acetate - DMSO dimethyl sulfoxide - PBS phosphate-buffered saline - HEPES 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid - BSA bovine serum albumin - FITC-Tf fluorescein isothiocyanate-labelled transferrin     

Improving protein extraction yield in reversed micellar systems through surface charge engineering

The mechanism of extraction of rat cytochrome b(5) from water into a sodium dioctylsulfosuccinate (AOT) micellar organic phase was studied using protein engineering of surface charged residues. The extraction behavior of native cytochrome b(5) and modified proteins with substitutions of the type glutamic acid --> lysine at positions 44 (E44K), 56 (E56K), and 92 (E92K), was studied as a function of pH. The results indicate that an important mechanism of extraction is an electrostatic interaction of this protein with the negatively charged surfactant. We demonstrate that it is possible to improve extraction by engineering the protein surface charge, increasing the driving force responsible for the protein transfer to the micellar phase. (c) 1994 John Wiley & Sons, Inc.     

Aerodynamic corrections for the flight of birds and bats in wind tunnels

Few wind tunnel studies of animal flight have controlled or corrected for distortions to behaviour, physiology or flight aerodynamics representing the difference between flight in the tunnel and flight in free air. Aerodynamic correction factors are derived based on lifting-line theory and the method of images for an animal flying freely within closed- and open-section wind tunnels; the method is very similar to that used to model flight in ground effect, and as in ground effect the corrections to induced drag may be substantial. These correction factors are used to estimate bound wing circulation, drag and mechanical power for comparison with free flight, and to derive testable predictions of optimum flight strategies for an animal in a tunnel. In an open-section tunnel, mechanical power is increased compared to free flight, and the animal should fly at the tunnel centre. In a closed tunnel mechanical power is usually reduced, and substantial savings are available, particularly at low speeds, if the animal flies close to the tunnel roof. Anecdotal observations confirm that birds and bats adopt this strategy. The mechanical power-speed curve in a closed tunnel is flatter than the curve for free flight, and this may explain the flat metabolic power-speed curves for birds and bats obtained in some measurements.     

The biodegradation of piperazine and structurally-related linear and cyclic amines

The biodegradability of a range of linear and cyclic amines was assessed. All proved to be biodegradable but there were interesting differences in their susceptibility. The least degradable was piperazine although piperazine-degrading microorganisms were of widespread occurrence in samples of water and activated sludge and, to a lesser extent, soils. Piperazine degraders are only present in very small numbers — on averageca. 0.8/ml of river water. Of six isolates capable of using piperazine as a sole source of carbon, nitrogen and energy in pure culture five were identified asMycobacterium spp. and one asArthrobacter sp., all strains were capable only of slow growth (mean generation time ofca. 30 to 40 hours) on this substrate. Piperidine, pyrrolidine, ethanolamine and diethanolamine were all readily biodegradable. The relationship between structure and degradability of amines is discussed as are the possible reasons for the relative recalcitrance of piperazine.