On the movement and distribution of calcium in white cabbage in dependence of the water status

Summary The uptake and distribution of Ca in white cabbage have been measured under controlled climatic conditions. The uptake of Ca has been determined by continuous -intensity measurements of⁴⁵Ca simultaneously at an outer transpiring leaf and at an inner head leaf. In the outer leaves the Ca content increased during the day in dependence of the transpiration amplitude. With-in the inner head leaves Ca was transported mainly during the night when the head mass additionally measured by -absorption increased due to the increasing plant water potential. At the end of the experiment the stable and active Ca concentration has been measured. re]19760823     

Association between proximity to the attending nephrologist and mortality among patients receiving hemodialysis

Background

Many Canadian patients who receive hemodialysis live far from their attending nephrologist, which may affect clinical outcomes. We investigated whether patients receiving hemodialysis who live farther from their attending nephrologist are more likely to die than those who live closer.

Methods

We studied a random sample of 18 722 patients who began hemodialysis between 1990 and 2000 in Canada. We calculated the distance between each patient''s residence location at the start of dialysis and the practice location of their attending nephrologist. We used Cox proportional hazards models to examine the adjusted relation between distance and clinical outcomes (death from all causes, infectious causes and cardiovascular causes) over a follow-up period of up to 14 years.

Results

During the follow-up period (median 2.5 yr, interquartile range 1.0–4.7 yr), 11 582 (62%) patients died. Compared with patients who lived within 50 km of their nephrologist, the adjusted hazard ratio of death among those who lived 50.1–150 km away was 1.06 (95% confidence interval [CI] 1.01–1.12), 1.13 (95% CI 1.04–1.22) for those who lived 150.1–300 km away and 1.13 (95% CI 1.03–1.24) for those who lived more than 300 km from their nephrologist (p for trend < 0.001). The risk of death from infectious causes increased with greater distance from the attending nephrologist (p for trend < 0.001). The risk of death from cardiovascular causes did not increase with distance from the attending nephrologist (p for trend = 0.21). Compared with patients who lived within 50 km of their nephrologist, the adjusted hazard ratio of death among those who lived more than 300 km away was 1.75 (95% CI 1.32–2.32) for infectious causes and 0.93 (95% CI 0.79–1.09) for cardiovascular causes.

Conclusions

Mortality associated with hemodialysis was greater among patients who lived farther from their attending nephrologist, as compared with those who lived closer. This was especially evident for death from infectious causes.In Canada, no one is denied renal replacement therapy because of their residence location; however, a substantial proportion of patients receiving dialysis live more than 300 km from the closest nephrologist.¹ Since this geographic barrier may make it more difficult to provide high-quality renal care, it is plausible that disparities in access to appropriate care may result in differences in health outcomes. Despite the potential implications for health policy, this issue has not been formally studied.We sought to examine this issue using data collected prospectively from patients who began hemodialysis in Canada between 1990 and 2000. We hypothesized that patients who lived farther away from their attending nephrologist would be more likely than patients who lived closer to die after starting dialysis.     

Phylogeography of the invasive seaweed Asparagopsis (Bonnemaisoniales, Rhodophyta) reveals cryptic diversity

The rhodophyte seaweed Asparagopsis armata Harvey is distributed in the northern and southern temperate zones, and its congener Asparagopsis taxiformis (Delile) Trevisan abounds throughout the tropics and subtropics. Here, we determine intraspecific phylogeographic patterns to compare potential causes of the disjunctions in the distributions of both species. We obtained specimens throughout their ranges and inferred phylogenies from the hypervariable domains D1-D3 of the nuclear rDNA LSU, the plastid spacer between the large and small subunits of RuBisCo and the mitochondrial cox 2-3 intergenic spacer. The cox spacer acquired base changes the fastest and the RuBisCo spacer the slowest. Median-joining networks inferred from the sequences revealed the absence of phylogeographic structure in the introduced range of A. armata, corroborating the species' reported recent introduction. A. taxiformis consisted of three nuclear, three plastid and four mitochondrial genetically distinct, lineages (1-4). Mitochondrial lineage 3 is found in the western Atlantic, the Canary Islands and the eastern Mediterranean. Mitochondrial lineages 1, 2, and 4 occur in the Indo-Pacific, but one of them (lineage 2) is also found in the central Mediterranean and southern Portugal. Phylogeographic results suggest separation of Atlantic and Indo-Pacific lineages resulted from the emergence of the Isthmus of Panama, as well as from dispersal events postdating the closure event, such as the invasion of the Mediterranean Sea by mitochondrial lineages 2 and 3. Molecular clock estimates using the Panama closure event as a calibration for the split of lineages 3 and 4 suggest that A. taxiformis diverged into two main cryptic species (1 + 2 and 3 + 4) about 3.2-5.5 million years ago (Ma), and that the separation of the mitochondrial lineages 1 and 2 occurred 1-2.3 Ma.     

Heme oxygenase-1 plays a pro-life role in experimental brain stem death via nitric oxide synthase I/protein kinase G signaling at rostral ventrolateral medulla

Background  

Despite its clinical importance, a dearth of information exists on the cellular and molecular mechanisms that underpin brain stem death. A suitable neural substrate for mechanistic delineation on brain stem death resides in the rostral ventrolateral medulla (RVLM) because it is the origin of a life-and-death signal that sequentially increases (pro-life) and decreases (pro-death) to reflect the advancing central cardiovascular regulatory dysfunction during the progression towards brain stem death in critically ill patients. The present study evaluated the hypothesis that heme oxygnase-1 (HO-1) may play a pro-life role as an interposing signal between hypoxia-inducible factor-1 (HIF-1) and nitric oxide synthase I (NOS I)/protein kinase G (PKG) cascade in RVLM, which sustains central cardiovascular regulatory functions during brain stem death.     

Determinants of parental care and offspring survival during the post-fledging period: males care more in a species with partially reversed sex roles

Sexual conflict is magnified during the post-fledging period of birds when the sexes face different trade-offs between continuing parental care or investing in self maintenance or other mating opportunities. Species with reversed sex roles provide a unique opportunity to study the relationship between mating systems and investment in parental care. Here, we provide the first detailed study of the length of care by males versus females (n = 24 pairs) during the post-fledging period, assessing factors that may promote care within and between the sexes. In the northern flicker Colaptes auratus, a species with partly reversed sex roles, males cared longer than females (average 16 versus 12 days, respectively). Overall, 36 % of females but no males deserted the brood prior to fledgling independence. Parents that provisioned nestlings at a high rate also spent more days feeding fledglings. Among males, age and nestling feeding rates were positively associated with the length of care. Among females, a low level of feather corticosterone (CORT_f) was associated with a longer length of care. About 45 % of fledglings died within the first week, but fledglings with intermediate body mass had the highest survival suggesting stabilizing selection on mass. Fledgling survival was also higher in individuals with larger broods and lower levels of CORT_f. We demonstrate that because females can be polyandrous they often desert the brood before males, and that the sexes respond to different cues relating to their energy balance when deciding the length of care given to their offspring.     

Influence of moisture, heat, and light stress on hydrogen fluoride fumigation injury to soybeans

Soybean (Glycine max (L) Merr.) plants were exposed to a single fumigation with hydrogen fluoride at concentrations sufficient to cause visible injury within 2 days. They were subjected to soil moisture or osmotic stress prior to, during, or after fumigation. Moisture stress before or during fumigation reduced injury because of stomatal closure and reduced fluoride uptake. Moisture stress after fumigation markedly accentuated the injury resulting from a single fumigation compared to plants kept continually under optimum soil moisture conditions. Full sunlight following the fumigation accentuated injury, while shade reduced it. Higher temperatures following fumigation also increased severity of symptoms.     

Global diversity and biogeography of Skeletonema species (bacillariophyta)

Recent studies have shown that the cosmopolitan diatom Skeletonema costatum sensu lato is composed of several morphologically and genetically distinct species. To assess whether the separate species have a cosmopolitan distribution, we analysed 184 strains from marine and estuarine sites worldwide. We identified the strains using light and electron microscopy, and we sequenced the hyper-variable region of nuclear LSU rDNA. All recently described species were genetically distinct, and all but two were morphologically distinct. Variability was found for the only ultrastructural character used to distinguish Skeletonema dohrnii and S. marinoi, which cannot be identified based on morphology alone. Furthermore, multiple genetically distinct taxa, which may represent cryptic species, were found within the S. menzelii and S. tropicum clades. We found that all currently recognized species of Skeletonema are widespread, however, gaps seem to occur in their geographical ranges. For example, some species are found in both the northern and southern temperate latitudes whereas other species appear to have only subtropical to tropical ranges. Skeletonema pseudocostatum and S. grethae seem to have more restricted geographical ranges because the former was not found along American coasts and the latter was encountered only in US waters. A taxonomic update is provided for Skeletonema strains currently available in several culture collections, which could aid reinterpretation of results obtained in comparative studies using these strains.     

Foraging Trade‐offs between Prey Size,Delivery Rate and Prey Type: How Does Niche Breadth and Early Learning of the Foraging Niche Affect Food Delivery?

Optimal foraging theory suggests that avian parents should prefer the most energetically efficient (largest) prey items when delivering food to offspring at a central place. However, during periods of high demand, selectivity of prey may decline, leading to the delivery of smaller and/or less nutritious items. We compared foraging trade‐offs between great tits (Parus major) which had a wider feeding niche than blue tits (Cyanistes caeruleus). We also compared the foraging efficiency of cross‐fostered young, which had learned the spatial foraging niche and prey size of the foreign species, to that of control conspecifics. Mean delivery rates did not differ between control and cross‐fostered parents of either species but as delivery rates increased, prey size declined for both species and both treatment groups. However, across the range of increasing delivery rates, parents were able to increase the total biomass of prey delivered. Cross‐fostering did not alter the proportion of different prey taxa in the diet, but cross‐fostered birds shifted the size of the prey taken to that of their foster species. Consistent with their broader feeding niche, great tits, but not blue tits, incorporated more unpalatable items (flies) as delivery rates increased. Although great tits foraged less efficiently in the blue tit niche, paradoxically, blue tits seem to deliver more prey biomass when foraging in the great tit niche.     

Functional analysis of amino acids of the Na+/H+ exchanger that are important for proton translocation

The Na⁺/H⁺ exchanger is an integral membrane protein found in the plasma membrane of eukaryotic and prokaryotic cells. In eukaryotes it functions to exchange one proton for a sodium ion. In mammals it removes intracellular protons while in plants and fungal cells the plasma membrane form removes intracellular sodium in exchange for extracellular protons. In this study we used the Na⁺/H⁺ exchanger of Schizosaccharomyces pombe (Sod2) as a model system to study amino acids critical for activity of the protein. Twelve mutant forms of the Na⁺/H⁺ exchanger were examined for their ability to translocate protons as assessed by a cytosensor microphysiometer. Mutation of the amino acid Histidine 367 resulted in defective proton translocation. The acidic residues Asp145, Asp178, Asp266 and Asp267 were important in the proton translocation activity of the Na⁺/H⁺ exchanger. Mutation of amino acids His98, His233 and Asp241 did not significantly impair proton translocation by the Na⁺/H⁺ exchanger. These results confirm that polar amino acids are important in proton flux activity of Na⁺/H⁺ exchangers.