Plasmolysis bays in Escherichia coli: are they related to development and positioning of division sites?

Plasmolysis bays, induced in Escherichia coli by hypertonic treatment, are flanked by zones of adhesion between the plasma membrane and the cell wall. To test the proposition of Cook et al. (W. R. Cook, F. Joseleau-Petit, T. J. MacAlister, and L. I. Rothfield, Proc. Natl. Acad. Sci. USA 84:7144-7148, 1987) that these zones, called periseptal annuli, play a role in determining the division site, we analyzed the positions of these zones by phase-contrast and electron microscopy. In situ treatment of cells grown in agar showed that the youngest cell pole was the most susceptible to plasmolysis, whereas the constriction site was resistant. Lateral bays occurred only at some distance from a polar bay or a resistant constriction site. Orienting cells with their most prominently plasmolyzed polar bay in one direction showed that the lateral bays were always displaced away from the polar bay at about half the distance to the other cell pole. If no poles were plasmolyzed, lateral bays occurred either in the centers of nonconstricting cells or at the 1/4 or 3/4 position of cell length in constricting cells. The asymmetric positions of lateral plasmolysis bays, caused by their abrupt displacement in the presence of polar bays or constriction sites, does not confirm the periseptal annulus model (Cook et al.), which predicts a gradual and symmetric change in the position of lateral bays with increasing cell length. Our analysis indicates that plasmolysis bays have no relation to the development and positioning of the future division site.     

Kinship and sociality in coastal river otters: are they related?

Previous studies of coastal river otters (Lontra canadensis)in Prince William Sound, Alaska, USA, documented atypical socialorganization for mammals. Social groups were composed largelyof males, but some males remained solitary year-round and mostfemales were asocial. Because, in carnivores, groups are usuallycomposed of highly related individuals but group living alsoprovides advantages unrelated to kinship, we concurrently evaluatedthe role of relatedness and ecological benefits in socialityamong coastal river otters. By using DNA microsatellite analysisand radiotelemetry, we were able to reject the hypothesis thatsocial groups of otters were kin based. In addition, we foundno indication of kin avoidance, as would be expected from lowdispersal and high local competition. Sociality conferred noreproductive benefits or costs to otters; number of offspringand number of relatives in the population did not differ betweensocial and solitary animals. Solitary males were not older orlarger than were social males, and there was no relation betweenmale size and number of offspring, indicating that sexual selectiondid not mask a potential relation between sociality and reproductivesuccess. Among coastal river otters in this region, socialitycould be explained by the benefits obtained from cooperativeforaging on high-quality schooling pelagic fishes. Such benefitsdid not require association with kin, resulting in no selectionpressure for kin-based groups. The prediction that the degreeof sociality in the population will fluctuate relative to theabundance of schooling pelagic fishes merits further investigation.     

Immunological abnormalities in haemophilia: are they caused by American factor VIII concentrate?

Scottish patients with haemophilia, most of whom had received no American factor VIII concentrate for over two years, were found to have immunological abnormalities similar to those in their American counterparts--that is, a reduced proportion of T helper cells, an increased proportion of T suppressor cells, and a reduced response to concanavilin A. Factor VIII from both the United States and Scotland severely inhibited the in vitro lymphocyte response to mitogens in patients and controls. The American and Scottish concentrates could not be distinguished in terms of either patient usage or their effect in vitro. These results argue against a disease vector specific to American blood products.     

Cancer and diet: How are they related?

Extensive research in the past decade has revealed cancer to be a multigenic disease caused by perturbation of multiple cell signalling pathways and dysregulation of numerous gene products, all of which have been linked to inflammation. It is also becoming evident that various lifestyle factors, such as tobacco and alcohol use, diet, environmental pollution, radiation and infections, can cause chronic inflammation and lead to tumourigenesis. Chronic diseases caused by ongoing inflammation therefore require chronic, not acute, treatment. Nutraceuticals, compounds derived from fruits, vegetables, spices and cereals, can be used chronically. This study discusses the molecular targets of some nutraceuticals that happen to be markers of chronic inflammation and how they can prevent or treat cancer. These naturally-occurring agents in the diet have great potential as anti-cancer drugs, thus proving Hippocrates, who proclaimed 25 centuries ago, 'Let food be thy medicine and medicine be thy food'.     

Phytoplankton configuration in six deep lakes in the peri-Alpine region: are the key drivers related to eutrophication and climate?

The aim of this study was to draw a general picture of the phytoplankton community in peri-Alpine lakes, including for the first time a broad data set of six deep peri-Alpine lakes, belonging to the same geographical region. The objective was to define the main key drivers that influence the phytoplankton community composition in this particular vulnerable region, for which the impacts of climate change have been demonstrated to be stronger than on a global average. The phytoplankton was investigated with a particular focus on cyanobacteria and using a classification approach based on morpho-functional groups. We hypothesized that phytoplankton in peri-Alpine lakes is mainly driven by nutrient loads as well as by water temperatures, variables that are strongly influenced by climate change and eutrophication. Though different phytoplankton configurations among lakes were partly due to their geographical (altitude) position, assemblages were mostly linked to temperature and nutrients. Furthermore, the results confirmed the significant role of the spring fertilization on the seasonal phytoplankton development. Cyanobacteria were related to the increasing annual average of air and water temperature gradient and therefore might become more important under future warming scenario. Air temperatures have a significant impact on water temperature in the uppermost meters of the water column, with a stronger influence on warmer lakes.     

Oxidative stress in acute pancreatitis: lost in translation?

Abstract

Oxidative stress has been implicated in the pathogenesis of acute pancreatitis, a severe and debilitating inflammation of the pancreas that carries a significant mortality, and which imposes a considerable financial burden on the health system due to patient care. Although extensive efforts have been directed towards the elucidation of critical underlying mechanisms and the identification of novel therapeutic targets, the disease remains without a specific therapy. In experimental animal models of acute pancreatitis, increased oxidative stress and decreased antioxidant defences have been observed, changes also detected in patients clinically. However, despite the promise of studies evaluating the effects of antioxidants in these model systems, translation to the clinic has thus far been disappointing. This may reflect many factors involved in the design of both preclinical and clinical evaluations of antioxidant therapy, not least the fact that most experimental studies have focussed on pre-treatment rather than post-injury assessment. This review has examined evidence relating to the involvement of oxidative stress in the pathophysiology of acute pancreatitis, focussing on experimental models and the clinical experience, including the experimental techniques employed and potential of antioxidant therapy.     

Has mortality related to alcohol decreased in Sweden?

In Sweden sales of alcohol dropped 17% from 1976 to 1982. Similarly, comparison of data from 1979 and 1982 shows that the mortality from cirrhosis of the liver declined appreciably, by 28% in men and 29% in women. During 1979-82 mortality from pancreatitis also declined noticeably, by 30% in men and 36% in women. By contrast, no decrease occurred in mortality from alcoholic psychosis, alcoholism, or alcohol intoxication. The decrease in mortality from cirrhosis of the liver and pancreatitis is probably explained by a decrease in the consumption of alcohol among an important subgroup of high consumers of alcohol. The lack of a decrease in mortality from alcoholic psychosis, alcoholism, and alcohol intoxication may be because such diagnoses are often made in socially deteriorated, more dependent alcoholic subjects who have not been able to reduce their consumption.     

Is group size related to longevity in mammals?

Life-history theory predicts that reduced extrinsic risk of mortality should increase species longevity over evolutionary time. Increasing group size should reduce an individual''s risk of predation, and consequently reduce its extrinsic risk of mortality. Therefore, we should expect a relationship between group size and maximum longevity across species, while controlling for well-known correlates of longevity. We tested this hypothesis using a dataset of 253 mammal species and phylogenetic comparative methods. We found that group size was a poor predictor of maximum longevity across all mammals, as well as within primates and rodents. We found a weak but significant group-size effect on artiodactyl longevity, but in a negative direction. Body mass was consistently the best predictor of maximum longevity, which may be owing to lower predation risk and/or lower basal metabolic rates for large species. Artiodactyls living in large groups may exhibit higher rates of extrinsic mortality because of being more conspicuous to predators in open habitats, resulting in shorter lifespans.     

Foraminifera and Cercozoa are related in actin phylogeny: two orphans find a home?

In recent years, the increased sampling of protein-coding genes from diverse eukaryotes has revealed that many aspects of each gene tree are at odds with other phylogenies. This has led to the belief that each gene tree has unique strengths and weaknesses, suggesting that an accurate picture of eukaryotic relationships will be achieved only through comparative phylogeny using several different genes. To this end, actin genes were characterized from two genera of chlorarachniophytes, Chlorarachnion and Lotharella, and three species of the cercomonad flagellate Cercomonas: Phylogenetic trees including these new actin genes confirm the recently proposed relationship between chlorarachniophytes and cercomonads (Cercozoa) and, more importantly, also show a close relationship between Cercozoa and Foraminifera. Both of these are major eukaryotic groups encompassing extremely diverse organisms, yet there is no strong evidence for the evolutionary position of either from morphological or molecular data. The union of Cercozoa and Foraminifera suggested by actin phylogeny represents a novel step in the long process of determining the broad relationships between all major eukaryotic groups.     

Hyponatremia: Is it related to the seasons?

BackgroundHyponatremia is a common electrolyte disorder in inpatients related to morbidity and mortality. In this study, we aimed to examine whether there is a relationship between the incidence of hyponatremia and the seasons among the patients hospitalized in our nephrology department.MethodsThe inpatients in our Nephrology Department between 2012 and 2015 were retrospectively analyzed. The patients with serum sodium levels below 135 mmol/L were included in the study. Hyponatremia incidence was calculated as the proportion of inpatients with low sodium levels in a season to the total number of inpatients in the same season.ResultsOut of 1950 inpatients in four years, 509 were found to have hyponatremia (26.1%). The mean serum sodium level of the patients was 129.7±4.7 mmol/L. Hyponatremia incidences in autumn, winter, spring, and summer were found to be 28.7%, 15.4%, 20.4%, and 36.6%, respectively. Upon comparing the incidence of hyponatremia in patients hospitalized in winter and summer seasons, there was a significantly higher incidence of hyponatremia in summer (p<0.001). We found a positive correlation between hyponatremia incidence and temperature (r=0.867, p=0.001). However, there was a negative correlation between hyponatremia incidence and relative humidity (r=-0.735, p=0.001).ConclusionsThe highest hyponatremia incidence was observed in summer in a four-year period. Loss of sodium by perspiration, along with increased temperature and/or excessive hypotonic fluid intake, might contribute to the development of hyponatremia.     

Acetylcholinesterase: how is structure related to function?

In accordance with its biological role, termination of neurotransmission at cholinergic synapses by rapid hydrolysis of the neurotransmitter, acetylcholine, acetylcholinesterase is one of nature's most efficient enzymes. Solution of its three-dimensional structure revealed that its active site is located at the bottom of a deep and narrow gorge. Such an architecture was unanticipated in view of its high turnover number. The present review examines how the highly specialized structure of acetylcholinesterase, with its sequestered active site, contributes to its catalytic efficacy, and discusses how the traffic of substrate and products to and from the active site is controlled.     

Individual aging and mortality rate: how are they related?

Many researchers working in the area of aging and longevity base their conclusions on the behavior of empirical age trajectories of mortality rates. In such analyses, changes in the slope of the logarithm of the mortality curve are often associated with changes in the rate of individual aging. We show that such interpretation may be incorrect: the changes in the slope of this curve do not necessarily correspond to the changes in the rate of individual aging. We use three models of mortality and aging to illustrate this statement. The first one is based on the idea of frailty. We show that changes in frailty distribution alone may be responsible for changes in the slope. The second model exploits the idea of saving lives. It evaluates changes in mortality rate after elimination of lethal stressful events. The third model uses the idea of Strehler and Mildvan (1960). It shows that changes in the rate of individual aging may take place without changes in the slope of the logarithm of the mortality curve.     

Is diabetes mellitus related to undernutrition in rural Tanzania?

OBJECTIVE--To investigate the relation between undernutrition and diabetes. DESIGN--Survey of glucose tolerance in rural Tanzania. SETTING--Eight villages in three widely separated regions of Tanzania. SUBJECTS--8581 people aged 15 and above: 3705 men and 4876 women. MAIN OUTCOME MEASURES--Oral glucose tolerance, body mass index, height, and low haemoglobin and cholesterol concentrations. RESULTS--In the eight villages 42.7-56.9% of all men and 30.0-45.2% of all women had a body mass index below 20 kg/m2; the lowest quintile was 18.2 kg/m2 in men and 18.6 kg/m2 in women. The prevalence of diabetes did not change significantly from the lowest to the highest fifths of body mass index in men (lowest 1.6% (95% confidence interval 0.8% to 2.9%) v highest 1.3% (0.7% to 2.5%)) or women (1.1% (0.6% to 2.1%) v 0.5% (0.2% to 1.2%)). In men and in women prevalence of impaired glucose tolerance was greater in the lowest fifths of height (8.2% (6.3% to 10.6%), and 11.1% (9.2% to 13.3%)) respectively and body mass index (9.6% (7.5% to 12.1%), and 8.4% (6.7% to 10.5%)) than in the highest fifths (impaired glucose tolerance 4.7% (3.4% to 6.5%); and 5.1% (3.9% to 6.7%); body mass index 5.1% (3.7% to 7.0%), and 7.7% (6.2% to 9.6%). CONCLUSION--Rates of diabetes were not significantly associated with low body mass index or height, but overall rates were much lower than those in well nourished Western populations. Increased impaired glucose tolerance in the most malnourished people may reflect the larger glucose load per kilogram weight. The role of undernutrition in the aetiology of diabetes must be questioned.     

Self-organization in relation to several similar concepts: are the boundaries to self-organization indistinct?

Self-organization is a concept and phenomenon whereby system-level patterns spontaneously arise solely from interactions among subunits of the system. Focusing on self-organization at the organismal level, I ask the question: are the boundaries to self-organization indistinct? After reviewing a number of published definitions of self-organization, I explore the conceptual boundaries among self-organization and two similar concepts, stigmergy and self-assembly. I highlight borderline cases that may blur the distinction among these and suggest that they may indeed be conceptually indistinct and difficult to separate in practice. Consequently, I propose a classification scheme based upon three aspects: whether the stimuli to which individuals respond are quantitative or qualitative, whether positive feedback is involved, and whether interindividual interactions are direct or indirect (stigmergic). In addition, I consider several other issues about self-organization, including (1) could a self-organized system use global information? (2) what is the role of the degree of correlation of activity among individuals? and (3) what is the role of positive feedback?