Background concentration of 226Ra in terrestrial animals

Evidence that environmental levels of vanadium are increasing hasraised concern over the injection of vanadium into the environmentfrom anthropogenic sources. Two simple global mass balance models(simulating current and pre-industrial conditions) were developed todemonstrate the influence of anthropogenic vanadium on the globaldistribution of this trace metal. Current vanadium emissions owing toman's current industrial activities were estimated to comprise 30% oftotal atmosphere loading, 3% of total ocean loading, and 6% of totalland loading. These loadings were always considerably less than thoseresulting from non-anthropogenic sources or events. Differences notedbetween the pre-industrial and current models were not sufficientlygreat to suggest that injection of anthropogenic vanadium constitutes asignificant environmental threat on a global scale.     

A meta-analysis of the effects of exercise and/or dietary restriction on resting metabolic rate

A meta-analysis was used to examine the independent and interactive effects of dietary restriction, endurance exercise training and gender on resting metabolic rate (RMR). Sixty different group means (covering 650 subjects) were identified from the scientific literature and subjected to meta-analysis techniques. Collectively (i.e., all groups combined), body weight loss was greater (P < 0.05) for men ( 18 kg) than for women ( 12 kg). There were no statistically significant exercise training or gender effects on RMR during weight loss. Collectively (i.e., all groups combined), dietary restriction resulted in a – 0.59 kJ min^–1 ( – 12%) decrease in RMR (P < 0.05). When normalized to body weight, RMR was reduced by less than 2% (P < 0.05). These data suggest that exercise training does not differentially affect RMR during diet-induced weight loss. In addition, decreases in resting metabolism appear to be proportional to the loss of the metabolically active tissue.     

Pattern and timing of evolutionary divergences among hominoids based on analyses of complete mtDNAs

We have examined and dated primate divergences by applying a newly established molecular/paleontological reference, the evolutionary separation between artiodactyls and cetaceans anchored at 60 million years before present (MYBP). Owing to the morphological transformations coinciding with the transition from terrestrial to aquatic (marine) life and the large body size of the animals (which makes their fossils easier to find), this reference can be defined, paleontologically, within much narrower time limits compared to any local primate calibration marker hitherto applied for dating hominoid divergences. Application of the artiodactyl/cetacean reference (A/C-60) suggests that hominoid divergences took place much earlier than has been concluded previously. According to a homogenous-rate model of sequence evolution, the primary hominoid divergence, i.e., that between the families Hylobatidae (gibbons) and Hominidae, was dated at 36 MYBP. The corresponding dating for the divergence betweenPongo (orangutan) andGorilla-Pan (chimpanzee)-Homo is 24.5 MYBP, that forGorilla vsHomo-Pan is 18 MYBP, and that forHomo vsPan 13.5 MYBP. The split between Sumatran and Bornean orangutans was dated at 10.5 MYBP and that between the common and pygmy chimpanzees at 7 MYBP. Analyses of a single gene (cytochromeb) suggest that the divergence within the Catarrhini, i.e., between Hominoidea and Old World monkeys (Cercopithecoidea), took place >40 MYBP; that within the Anthropoidea, i.e., between Catarrhini and Platyrrhini (New World monkeys), >60 MYBP; and that between Anthropoidea and Prosimii (lemur), 80 MYBP. These separation times are about two times more ancient than those applied previously as references for the dating of hominoid divergences. The present findings automatically imply a much slower evolution in hominoid DNA (both mitochondrial and nuclear) than commonly recognized.     

Measurement of the carrying capacity of benthic habitats using a metabolic-rate based index

Carrying capacities of grazed habitats are typically expressed as numbers or biomass of animals per unit area; however, such parameters are appropriate only when the body size of animals is constant because consumption and other metabolic-rate based parameters such as respiration and production are proportional to body mass raised by a power of 0.75 rather than 0 or 1. Habitat carrying levels are therefore better expressed in the form of an index of total community consumption by summing the body masses of individual animals after they have been scaled using a biomass exponent of 0.75. A parameter scaled in this way,P ₂₀, varied in a predictable manner when calculated for the mobile epifaunal assemblages associated with rope fibre habitats placed at marine and estuarine sites;P ₂₀ showed no significant difference between 17 shallow, clear-water sites worldwide, but declined consistently when photosynthesis was reduced.P ₂₀ also did not vary significantly when calculated for the mobile epifaunal communities associated with fourAmphibolis antarctica seagrass habitats in Australia ( = 100 µg ·g^–1 · day^–1), and reached but did not significantly exceed a ceiling of 280 g · g^-1 · day^-1 forSargassum plants. These results are consistent with the hypothesis that the production of shallow-water epifaunal communities of grazers is constrained by resource ceilings which can be quantified using metabolic-rate based indices. If this production ceiling hypothesis is correct then diffuse competition is generally more important than predation or environmental disturbance in restricting the growth of mobile epifaunal populations.     

Performance and seasonal abundance of the neotropical brown stink bug, shape Euschistus heros nymphs and adults on a novel food plant (pigeonpea) and soybean

Pigeonpea, Cajanus cajan (L.) Millsp. (Leguminosae) was found as a novel food plant of the neotropical brown stink bug, Euschistus heros (F.), in Paraná State, Brazil. Laboratory studies indicated nymphs performing better when fed on immature pods of soybean, Glycine max (L.) Merrill (Leguminosae), than on immature pods of pigeonpea. Female nymphs required 1.7 d less to complete development and tended to have a lower mortality on soybean (17.5%) than on pigeonpea (25.0%). At emergence, fresh body weight was greater on soybean than on pigeonpea. Adult E. heros performed better on soybean than on pigeonpea. After 120 d, 35% of adults were alive on soybean and 30% on pigeonpea; 93.3% of females oviposited on soybean, and 73.3% on pigeonpea, with an oviposition delay of 17 days on pigeonpea compared to soybean. Fecundity was 63% greater on soybean than on pigeonpea, and adult body weight gain for females and males at different ages was 6–36% greater on soybean than on pigeonpea. E. heros colonized soybean during January–March, from the pod-setting and filling stages (R3–R6) to maturity (R7–R8), and pigeonpea during April–June. These results indicate that E. heros has expanded its host range to pigeonpea in Brazil; pods of this plant are suitable food, and can support the insect during autumn-early winter, after soybean harvest, and before it enters into partial hibernation.     

Effects of seed distribution and competitors on seed harvesting efficiency in heteromyid rodents

Summary The foraging strategies of four naturally co-existing heteromyid rodent species were investigated: Dipodomys deserti (100 g), D. merriami (38 g), Microdipodops pallidus (13 g), and Perognathus longimembris (7 g). In 208 over-night laboratory foraging trials animals were provided with millet seed distributed in clumped and scattered patterns. Net removal of seeds from the foraging arena and amounts of seeds in cheek pouches and in caches were determined. When alone in an areana none of these species specialized extensively on either clumped or scattered seeds, although each tended to take more clumped than scattered seeds. When placed together with other individuals, animals once again tended to cache more clumped than scattered seeds in all but one paired combination of species: P. longimembris cached more scattered than clumped seeds when opposed by D. deserti. This suggests that the smaller species obtained a less preferred distribution of seeds in the face of competition. The two smaller species showed a great reduction in general foraging success in the presence of either of the two larger species. In general, a species cached less seeds when faced by larger opponent species.     

Competition for nitrogen in a tussock tundra ecosystem

Summary The objective was to measure the competition for nitrogen among vascular plants, mosses, and soil microbes along a continuum of nitrogen availability, induced by carbon and nitrogen amendments, in a tussock tundra ecosystem.¹⁵N was used as a tracer. Vascular plants showed an increasing¹⁵N recovery with increasing time and with increasing nitrogen availability; the latter suggests that nitrogen was limiting vascular plant growth. Green mosses took up¹⁵N initially, but showed no significant trends with either treatment or time. There was a higher¹⁵N recovery in the soil insoluble compartment for the carbon-amended treatment than in the nitrogen-amended treatments; this suggested that carbon as an energy source limited microbial activity. After two months, the relative¹⁵N recovery fell in the order: soil microbes (79%)>vascular plants (16%) >green mosses (2%).     

Carbohydrate status in roots of two soybean cultivars: A possible parameter to explain different efficiencies concerning phosphate uptake

The carbohydrate levels in the roots of two soybean cultivars (Century, Woodworth) were determined during the early vegetative growth stage. Based on Michaelis-Menten kinetics Century was characterized as being more efficient at phosphate uptake when compared to Woodworth. The experiments were carried out at normal nutrition (+P treatment) as well as under a condition of moderate phosphate stress (–P treatment). The stress situation was created by withdrawal of phosphate from the nutrient solution for five or nine days. Compared to the +P-treatment the deprivation of phosphate led to a reduction of more than 50% in the phosphate content of the plant tissue.The carbohydrates in the roots exhibited differences between both cultivars with Century generally having higher sucrose levels. During the morning the +P treatment of Century exhibited 10 mg g^-1 and in the afternoon 16 mg g^-1 sucrose (plant dry weight basis). This compares to 8 mg g^-1 sucrose (morning) and 13 mg g^-1 sucrose (afternoon) for Woodworth. Phosphate stress increased the levels of hexoses (glucose, fructose) in both varieties significantly. The sucrose levels remained higher for the Century variety even during phosphate stress. We conclude that the shoot of the Century variety supplies its root with an increased amount of energy in form of carbohydrates compared to the Woodworth variety. This may enable the plant to take up phosphate more efficiently. It is also remarkable that the Century variety reduces the pH of the nutrient medium more rapidly. This active proton deposition may create a high membrane potential which is known to be necessary for phosphate uptake.     

Differences exist in bird communities using restored and natural wetlands in the Parkland region,Alberta, Canada

Wetland restoration is used to compensate for historic and ongoing wetland losses. We compared bird community composition in 24 restored wetlands and 36 natural wetlands in the Parkland region of Alberta. Natural wetlands ranged in exposure to agricultural activity and were binned into three classes (low, medium, and high disturbance). Although the abundance and average species richness of birds were similar between restored and natural wetlands (analysis of variance: p > 0.22), the avian community composition differed significantly among wetland types (multiresponse permutation procedure [MRPP]: A = 0.05, p < 0.001). The avifauna using restored wetlands was distinct from the avifauna using natural wetlands spanning a range of disturbance levels (A = 0.02–0.06; p ≤ 0.006). Notably, restored wetlands were surrounded by less shrub/forest cover and more open water than low‐disturbance, natural wetlands. The majority (58%) of species using the surveyed wetlands were not classified as wetland‐dependent. Interestingly, if only wetland‐dependent species are considered, the avifauna using restored wetlands is no longer distinctive (MRPP: A < 0.01, p = 0.187), although the abundance of wetland‐dependent birds was marginally higher in restored wetlands (n = 24) than in low‐disturbance, natural wetlands (n = 10; Tukey's honestly significant difference test: p = 0.041). Overall, restored wetlands had reduced beta diversity compared to natural wetlands, regardless of whether the avifauna were restricted to wetland‐dependent species or considered comprehensively. This draws into question the legitimacy of the assumption that restoration can fully offset continued losses of natural wetlands.     

Osmotic Forces and Gap Junctions in Spreading Depression: A Computational Model

In a computational model of spreading depression (SD), ionic movement through a neuronal syncytium of cells connected by gap junctions is described electrodiffusively. Simulations predict that SD will not occur unless cells are allowed to expand in response to osmotic pressure gradients and K⁺ is allowed to move through gap junctions. SD waves of [K⁺]_out 25 to 60 mM moving at 2 to 18 mm/min are predicted over the range of parametric values reported in gray matter, with extracellular space decreasing up to 50%. Predicted waveform shape is qualitatively similar to laboratory reports. The delayed-rectifier, NMDA, BK, and Na⁺ currents are predicted to facilitate SD, while SK and A-type K⁺ currents and glial activity impede SD. These predictions are consonant with recent findings that gap junction poisons block SD and support the theories that cytosolic diffusion via gap junctions and osmotic forces are important mechanisms underlying SD.     

Structure of the fission yeast centromere cen3: Direct analysis of the reiterated inverted region

We determined the structure of the Schizosaccharomyces pombe centromere cen3 using direct genomic mapping and cosmid walking. The repetitive region of cen3 is approximately 110 kb, much longer than that of the previously determined cen1 and cen2 regions. The 30 kb long left and 60 kb right repetitive sequences are arranged with an inverted symmetry and flank the 1520 kb central domain. The repeat motifs in cen3, although they consist of the common centromeric repeat elements, are slightly different from those in cen1 and cen2. The cen3 repeat motifs appear to be reiterated four times in the left and nine times in the right side repetitive regions. We found that the central domain consists of the common 5 kb core sequence associated with the pair of innermost inverted sequences, most of which are reiterated only twice in the genome. Although their sizes differ significantly, the general features of cen1, cen2 and cen3 are similar, and a prototype, consensus structure for the fission yeast centromere may be deduced.by J.A. Huberman     

Upland burning and grazing as strategies to offset climate-change effects on wetlands

Wetland ecosystems perform a multitude of services valued by society and provide critical habitat for migratory birds and other wildlife. Despite their importance, wetlands have been lost to different local, regional, and global drivers. Remaining wetlands are extremely sensitive to changing temperature and precipitation regimes. Management of grassland areas in wetland catchments may be an effective strategy for counteracting potentially negative impacts of climate change on wetlands. Our objective was to estimate the effects of climate changes on wetland hydrology, and to explore strategies for increasing surface-water inputs to wetlands. We coupled a field study with process-based simulation modeling of wetland-water levels. We found that climate change could decrease the number of wetlands that hold ponded water during the waterfowl breeding season by 14% under a hot wet scenario or 29% under a hot dry scenario if no upland-management actions were taken. Upland burning reduced pond losses to 9% (hot wet) and 26% (hot dry). Upland grazing resulted in the smallest loss of ponded wetlands, 6% loss under the hot-and-wet scenario and 22% loss under the hot-and-dry scenario. Overall, water inputs could be increased by either burning or grazing of upland vegetation thereby reducing pond losses during the waterfowl breeding season. While field results suggest that both grazing and burning can reduce the vegetative structure that could lead to increases in runoff in grassland catchments, our model simulations indicated that additional actions may be needed for managers to minimize future meteorologically driven water losses.

     

Anuran occupancy of created wetlands in the Central Appalachians

Evaluating the adequacy of created wetlands to replace the functions of lost natural wetlands is important because wetland mitigation is a major tool used to offset wetland losses. However, measurements such as vegetative cover and presence of wildlife may not provide sufficient evidence that created wetlands are functioning properly and thus examining the ecology of wetland biota such as that of amphibians may be a more useful surrogate for function. The objectives of this study were to compare the occupancy and detection of calling anurans in created wetlands relative to beaver-created wetlands. Five-, 10-min, and broadcast call surveys were performed at 24 wetlands throughout the Central Appalachians once every month from March through August of 2009 and 2010. Occupancy modeling was used to estimate the occupancy and detection of individual species, incorporating relevant environmental variables. The occupancy of anurans did not differ between human-created and beaver (Castor canadensis)-created wetlands. Detection of anurans was largely unaffected by call survey type, but several environmental covariates had a significant effect on the detectability of calling anurans. Our results suggest that the function of providing adequate chorusing habitat for adult anurans is being fulfilled by the created wetlands that we examined.     

Characterization of two different Ca2+ uptake and IP3-sensitive Ca2+ release mechanisms in microsomal Ca2+ pools of rat pancreatic acinar cells

We have examined the effect of the Ca²⁺ (Mg²⁺)-ATPase inhibitors thapsigargin (TG) and vanadate on ATP-dependent ⁴⁵Ca²⁺ uptake into IP₃-sensitive Ca²⁺ pools in isolated microsomes from rat pancreatic acinar cells. The inhibitory effect of TG was biphasic. About 40–50% of total Ca²⁺ uptake was inhibited by TG up to 10 nm (apparent K_i4.2 nm, Ca²⁺ pool I). An additional increase of inhibition up to 85–90% of total Ca²⁺ uptake could be achieved at 15 to 20 nm of TG (apparent K_i12.1 nm, Ca²⁺ pool II). The rest was due to TG-insensitive contaminating plasma membranes and could be inhibited by vanadate (apparent K_i10 m). In the absence of TG, increasing concentrations of vanadate also showed two phases of inhibition of microsomal Ca²⁺ uptake. About 30–40% of total Ca²⁺ uptake was inhibited by 100 m of vanadate (apparent K_i18 m, Ca²⁺ pool II). The remaining 60–70% could be inhibited either by vanadate at concentrations up to 1 mm (apparent K_i300 m) or by TG up to 10 nm (Ca²⁺ pool I). The amount of IP₃-induced Ca²⁺ release was constant at 25% over a wide range of Ca²⁺ filling. About 10–20% remained unreleasable by IP₃. Reduction of IP₃ releasable Ca²⁺ in the presence of inhibitors showed similar dose-response curves as Ca²⁺ uptake (apparent K_i 3.0 nm for IP₃-induced Ca²⁺ release as compared to 4.2 nm for Ca²⁺ uptake at TG up to 10 nm) indicating that the highly TG-sensitive Ca²⁺ pump fills the IP₃-sensitive Ca²⁺ pool I. At TG concentrations >10 nm which blocked Ca²⁺ pool II the apparent K_i values were 11.3 and 12.1 nm, respectively. For inhibition by vanadate up to 100 m the apparent K_i values were 18 m for Ca²⁺ uptake and 7 m for Ca²⁺ release (Ca²⁺ pool II). At vanadate concentrations up to 1 mm the apparent K_i values were 300 and 200 m, respectively (Ca²⁺ pool I). Both Ca²⁺ pools I and II also showed different sensitivities to IP₃. Dose-response curves for IP₃ in the absence of inhibitors (control) showed an apparent K_m value for IP₃ at 0.6 m. In the presence of TG (inhibition of Ca²⁺ pool I) the curve was shifted to the left with an apparent K_m for IP₃ at 0.08 m. In the presence of vanadate (inhibition of Ca²⁺ pool II), the apparent K_m for IP₃ was 2.1 m. These data allow the conclusion that there are at least three different Ca²⁺ uptake mechanisms present in pancreatic acinar cells: TG- and IP₃ insensitive but highly vanadate-sensitive Ca²⁺ uptake occurs into membrane vesicles derived from plasma membranes. Two Ca²⁺ pools with different TG-, vanadate- and IP₃-sensitivities are most likely located in the endoplasmic reticulum at different cell sites, which could have functional implications for hormonal stimulation of pancreatic acinar cells.This work was supported by the Deutsche Forschungsgemeinschaft, Sonderforschungsbereich 246. The authors wish to thank Dr. KlausDieter Preuß for valuable discussions and Mrs. Gabriele Mörschbächer for excellent secretarial help.     

The nucleotide sequence of the mitochondrial DNA molecule of the grey seal,Halichoerus grypus,and a comparison with mitochondrial sequences of other true seals

The sequence of the mtDNA of the grey seal, Halichoerus grypus, was determined. The length of the molecule was 16,797 base pairs. The organization of the molecule conformed with that of other eutherian mammals but the control region was unusually long due to the presence of two types of repeated motifs. The grey seal and the previously reported harbor seal, Phoca vitulina, belong to different but closely related genera of family Phocidae, true (or earless) seals. In order to determine the degree of differences that may occur between mtDNAs of closely related mammalian genera, the 2 rRNA genes, the 13 peptide coding genes, and the 22 tRNA genes of the 2 species were compared. Total nucleotide difference in the peptide coding genes was 2.0–6.1%. The range of conservative difference was 0.0–1.5%. In the inferred peptide sequences the amino acid difference was 0.0–4.5%, and the difference with respect to chemical properties of amino acids was 0.0–3.0%. A gene that showed a limited degree of difference in one mode of comparison did not necessarily show a corresponding limited difference in another mode. The ratio for differences in codon positions 1, 2, and 3 was 2.7:1:16. The corresponding ratio for conservative differences was 1.8:1. l:1. The evolutionary separation of the two species was calculated to have taken place 2–2.5 million years ago. This dating gives the figure 8 × 10^–9 as the mean rate of substitution per site and year in the entire mtDNA molecule. Comparison with the cytochrome b gene of the Hawaiian monk seal and the Weddell seal suggested that the lineage of these two species and that of the grey and harbor seals separated 8 million years ago. Correspondence to: Ú. Árnason     

Symbiotic functioning,structural adaptation,and subcellular organization of root nodules from <Emphasis Type="Italic">Psoralea pinnata</Emphasis> (L.) plants grown naturally under wetland and upland conditions in the Cape Fynbos of South Africa

In the Cape Fynbos of South Africa, Psoralea pinnata (L.) plants occur naturally in both wetland and well-drained soils and yet effectively fix N₂ under the two contrasting conditions. In this study, nodule structure and functioning in P. pinnata plants from the two habitats were evaluated using light and transmission electron microscopy (TEM), as well as the ¹⁵N natural abundance technique. The results showed that, structurally, fully developed P. pinnata nodules were spherical in shape with six components (namely, lenticels, periderm, outer cortex, middle cortex, inner cortex, and a central bacteria-infected medulla region). Morphometric analysis revealed 44 and 84 % increase in cell area and volume of wetland nodules compared to those from upland. The percentage area of nodules occupied by the middle cortex in wetland nodules was twice that of upland nodules. As a result, the size of the medulla region in wetland nodules was significantly reduced compared to upland nodules. Additionally, the average area of medulla occupied by intercellular air spaces in wetland nodules was about five times that of upland nodules (about 431 % increase in wetland over upland nodules). TEM data also showed more bacteroids in symbiosomes of upland nodules when compared to wetland nodules. However, isotopic analysis of above-ground plant parts revealed no differences in symbiotic parameters such as N concentration, ?¹⁵N and %Ndfa between wetland and upland P. pinnata plants. These results suggest that, under limiting O₂ conditions especially in wetlands, nodules make structural and functional adjustments to meet the O₂ demands of N₂-fixing bacteroids.     

A note on the kinetics of uptake of d-glucose by the food yeast,Candida utilis

Unlike other yeasts so far investigated, the d-glucose carrier of Candida utilis (strain NCYC 737) appears to change affinity for d-glucose according to its exogenous concentration. When the concentration of d-glucose was <0.4 mM, the apparent K _m 0.2 mM; at >0.4 mM, the K _m 10 mM.     

Blue through UV polarization sensitivities in insects

A Signal-to-Noise optimization model has now been extended to explain the range of species-specific polarization sensitivities of insects. The different polarization sensitivities are shown to represent optimizations for the detection of plane polarized (Rayleigh-scattered) skylight over a range of atmospheric polarization conditions. Rhodopsin absorption spectra with peaks in the Blue (max450 nm) maximize detection efficiencies under conditions of high polarization. Rhodopsin absorption spectra peaking in the UV (max350 nm) maximize Signal-to-Noise Ratios for the detection of polarized skylight at the other extreme of low polarization.     

The limits of phosphorus removal in wetlands

The phosphorus concentrations exported from wetlands are explored via data and a first order model. The graph of outlet concentration versus areal phosphorus loading is used to display these data and the model. For a given wetland, data and models show that P concentrations show an S curve response to increasing P loadings. The lower plateau is the background concentration and the upper plateau is the inlet concentration. The position of the ascending limb between the two plateaus is positioned differently for different wetlands. Phosphorus (P) removal in wetlands is often typified by a stable decreasing gradient of P concentrations from inlet to outlet, and an accompanying stable decreasing gradient in P assimilation. Limits to removal are inherent in the physical, chemical and biological processes. A lower outlet concentration limit exists because of the P cycle in the un-impacted wetland. The loading at which the outlet concentration departs from background, the lower knee in the loading curve, varies from wetland to wetland. An upper outlet concentration limit is imposed by the source concentration for extremely high inflows. The first order mass balance equation interpolates between these limits. The model gives further insights about performance within an overall envelope. The water carrying capacity of the wetland precludes flows in excess of the hydraulic conveyance capacity, thus limiting the possible P loadings to the system. Conversely, extremely low hydraulic loadings cause the wetland to be dominated by atmospheric additions and losses. The central tendency of inter-system data in the North American Database is shown to be inadequate to draw generalized conclusions about ecosystem processes in an individual wetland. The proposed one gram rule of Richardson, et al. (1997) is shown to be an over-simplification.