Plankton and seston of a Colorado (U.S.A.) alpine lake: The winter anomaly and the inlet-outlet budget

Long Lake, Colorado, at an altitude of 3209 m, is oligotrophic and has an annual ice cover of 240 days. Greatest phytoplankton biomass (mostly μ-algae) was attained in April and May under thick ice and snow. The Zooplankton was sparse; Cyclops was most abundant in winter, but cladocerans and rotifers had no seasonal maxima. The lake had a total water replacement of 38.7 times per year. Heavy June runoff flushes cut more than 99% of the plankton. On an annual basis, about twice as much plankton biomass is lost through the outlet as comes in through the inlet. Total monthly organic seston sedimentation (fallout) rates for the whole lake ranged from 16.1 kg in October to 730.8 kg in June. Total annual seston production (balance) was 8.0 g organic matter or 4.24 g carbon/m².     

Silver enhances stamen development in female white campion (Silene latifolia [Caryophyllaceae])

Sex expression in the dioecious plant white campion (Silene latifolia Poiret subsp. alba) appears to be insensitive to exogenous applications of auxins, cytokinins, gibberellic acid, and ethylene; however, silver thiosulfate (Ag(2)S(2)O(3)), an ethylene inhibitor, enhanced stamen development in female white campion. In wild-type females, stamen development is arrested before the microspore mother cells are formed. In contrast, stamens of Ag(2)S(2)O(3)-treated females completed meiosis and produced microspores. Stamen development for these females was incomplete, however, and pollen did not mature. Ag(2)S(2)O(3) stimulated stamen development to the same extent in asexual white campion mutants that retained a Y chromosome but had lost Y-linked genes needed for early stages of stamen development. Although Ag(2)S(2)O(3) can inhibit ethylene signaling, the enhancement of stamen development in female white campion cannot be explained as a loss of ethylene response because no other ethylene inhibitor tested (1-methylcyclopropene, trans-cyclooctene, aminoethoxyvinylglycine, and cobalt chloride) caused stamens to develop in female plants. In addition, application of other metal ions could not enhance stamen development. Therefore, the effect we observed on female white campion was specifically caused by silver ions but not by their action on ethylene signaling.     

On the Combined Analysis of H and N/H Solid-State NMR Data for Determination of Transmembrane Peptide Orientation and Dynamics

The dynamics of membrane-spanning peptides have a strong affect on the solid-state NMR observables. We present a combined analysis of ²H-alanine quadrupolar splittings together with ¹⁵N/¹H dipolar couplings and ¹⁵N chemical shifts, using two models to treat the dynamics, for the systematic evaluation of transmembrane peptides based on the GWALP23 sequence (acetyl-GGALW(LA)₆LWLAGA-amide). The results indicate that derivatives of GWALP23 incorporating diverse guest residues adopt a range of apparent tilt angles that span 5°–35° in lipid bilayer membranes. By comparing individual and combined analyses of specifically ²H- or ¹⁵N-labeled peptides incorporated in magnetically or mechanically aligned lipid bilayers, we examine the influence of data-set size/identity, and of explicitly modeled dynamics, on the deduced average orientations of the peptides. We conclude that peptides with small apparent tilt values (<∼10°) can be fitted by extensive families of solutions, which can be narrowed by incorporating additional ¹⁵N as well as ²H restraints. Conversely, peptides exhibiting larger tilt angles display more narrow distributions of tilt and rotation that can be fitted using smaller sets of experimental constraints or even with ²H or ¹⁵N data alone. Importantly, for peptides that tilt significantly more than 10° from the bilayer-normal, the contribution from rigid body dynamics can be approximated by a principal order parameter.     

A disulfide-bonded short chain collagen synthesized by degenerative and calcifying zones of bovine growth plate cartilage

Studies of collagen synthesis by specific sections of individual fetal bovine costochondral junction growth plates were conducted and histologically related to the zones from which the sections were derived. Sections were metabolically labeled in organ culture to examine the synthesis of collagen and its precursors. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed that Type II collagen was the major species synthesized in all tissue sections; 1 alpha, 2 alpha, 3 alpha collagen chains were synthesized in all growth plate sections and to a small extent in the fetal structural cartilage. A short chain collagen was synthesized predominantly in the zones of degeneration and provisional calcification and accounted for 8-12% of the radioactivity in this section. This short chain collagen has 63-kDa subunits which are converted to 46-kDa species by limited proteolysis with pepsin. Two-dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis demonstrated that both the pepsin- and non-pepsin-treated forms of short chain collagen are disulfide-bonded. Digestion with bacterial collagenase showed that the 46-kDa and a major portion of the 63-kDa forms are collagenous. Pulse-chase studies in organ culture did not demonstrate an obvious precursor to the 63-kDa form, and there was no conversion to the 46-kDa after 20 h. Synthesis of short chain collagen appears to be specific to the process of endochondral ossification in the growth plate; its appearance may be critical to this transition process.     

A Comparison of the Iron Bonding in Anhydrohemoglobin and Anhydromyoglobin

Mössbauer effect measurements show that the ferrous ions in dehydrated deoxymyoglobin are in the high spin state while those in dehydrated deoxyhemoglobin (AHb) are equally distributed between high and low spin states. It is concluded that the two spin states present in AHb are associated with the iron site difference of the α- and β-chains.     

Beta2 Adrenergic Receptor (ADRβ2) Haplotype Pair (2/4) Is Associated with Severe Asthma

Background

β2 adrenergic receptor (ADRβ2) polymorphisms including ADRβ2+46G>A have been reported to cause adverse outcomes in mild asthmatics. The extent to which ADRβ2 polymorphisms and in particular their haplotypes contribute to severe asthma is unknown.

Objective

To determine the association of ADRβ2 polymorphisms and haplotypes with asthma severity.

Methods

Caucasians (n = 2979) were genotyped for 11 ADRβ2 polymorphisms. The cohort (mean age 39.6, 60% female) included 2296 non-asthmatics, 386 mild asthmatics, 172 moderate asthmatics and 125 severe asthmatics. Haplotype frequency and haplotype pair for each subject was determined using the PHASE algorithm.

Results

The three asthmatic cohorts were comparable in age and gender but were distinguishable from each other in terms of symptoms, spirometry, medication use and health care utilisation (p <0.001). None of the polymorphisms showed a genotypic or allelic association with asthma diagnosis or severity. Nine haplotypes were identified and no association was found with asthma diagnosis or severity per se. Haplotype pair 2/4 was associated with asthma severity (Trend Test, OR 1.42, p = 0.0008) but not with asthma per se. Prevalence of haplotype pair 2/2 appeared to decrease with asthma severity (Trend Test, OR 0.78, p = 0.067). Two new haplotypes were identified, occurring exclusively in asthmatics at a frequency of ≥ 1%. In addition, a positive association between carriage of ADRβ2 +523*C and increased risk of atopy was discovered.

Conclusions

ADRβ2 haplotype pair 2/4 is associated with severe asthma and is consistent with findings of poor bronchodilator response in mild asthmatics who are also haplotype 2/4.     

Seed banks of a southern Australian wetland: the influence of water regime on the final floristic composition

The sediments of a southern Australian wetland complex were investigated to determine the germinable seed bank. The number of seeds ranged from 22,000 to 78,000 m^–2. Non-metric multi dimensional scaling (NMS) ordination based upon species composition separated the four basins but each contained the representatives of the major functional groups: terrestrial, amphibious and submerged. To test the influence of water regime on the final floristic composition derived from these seed banks, sediments were positioned at three elevations (0, 30 and 80 cm) and subjected to three hydrologic regimes (static water level, and draw down rates of 2.5 and 7 cm week^–1). Species compositions were analysed after 98 days via ordination. Despite significant differences in the initial seed bank composition the final floristic compositions were correlated with the water regime and independent of the initial seed bank composition. Species groups were segregated on a basis of whether sediments were continuously exposed to the atmosphere, the rate of draw down and the water depth. Moist sediments were dominated by species belonging to all the main functional groups. Sediments subject to rapid drying were dominated by terrestrial species whereas sediments that were flooded for the majority of the time were dominated by submerged species.