Crown age estimation of a monocotyledonous tree species Dracaena cinnabari using logistic regression

Unique woodlands of Dracaena cinnabari (DC) are at risk throughout most of their range (Socotra Island, Yemen) as a result of missing regeneration and overmaturity. Effective conservation measures depend on reliable predictions of future population dynamics, which depend on accurate data on current age structure. However, age determination of Dracaena sp. has long been a scientific challenge, because the common method of tree ring counts cannot be applied to this or to most other monocotyledonous trees. In the present study, the indirect method for crown age estimation proposed by Adolt and Pavlis (Trees 18:43–53, 2004) was further developed using a more appropriate statistical technique and an intuitive model formulation. This new technique is based on the relationship between the number of branching orders and the number of flowering events that result from a specific growth pattern. We used logistic regression to directly model annual flowering probability, the reciprocal value of which corresponds to the length of the interval between flowering events. Our methodology was applied to data sets collected at two ecologically distinct sites. In Firmihin, the time between flowering events decreases from 28?years between the first and second event to 10?years between the 25th and 26th event. The length of time between flower events in Skant, however, was estimated to be a constant value of 6.5?years. We propose the application of generalised mixed-effects models and methods of survey sampling to improve the accuracy of crown age estimation in DC. Our methodology may also be useful for age estimations of other tree species with similar growth patterns, such as Dracaena draco and Aloe dichotoma.     

Biotechnological methods of <Emphasis Type="Italic">in vitro</Emphasis> propagation in willows (<Emphasis Type="Italic">Salix</Emphasis> spp.)

Many populations of high-mountainous relic dioecious willows in Central Europe only consist of female individuals and are thus limited in their reproductive potential. We completed micropropagation experiments with shoot apexes and nodal segments of common and endangered willow (Salix) species, which can help to reintroduce autochthonous genotypes to their natural sites. Until recently, cultivation of green young shoot apexes of S. alba and S. lapponum showed the highest percentage of regeneration. We successfully applied the two-times-sterilisation due to high contamination of natural explants. The OK medium was the most efficient culture medium. In vitro propagation of willows with unisexual catkins, anther and ovule cultures were tested and optimised. Isolated anthers were cultivated on selected media and then microcallus and calluses of S. caprea and calluses of S. viminalis were formed on the A medium. Among various tested and optimised media for the ovule culture, the CP medium was the most efficient one. In this case, only the microcalluses of S. viminalis were observed. We developed biotechnological procedures that can be useful in conserving fragmented populations of high-mountainous willows.     

Calcium Influx Rescues Adenylate Cyclase-Hemolysin from Rapid Cell Membrane Removal and Enables Phagocyte Permeabilization by Toxin Pores

Bordetella adenylate cyclase toxin-hemolysin (CyaA) penetrates the cytoplasmic membrane of phagocytes and employs two distinct conformers to exert its multiple activities. One conformer forms cation-selective pores that permeabilize phagocyte membrane for efflux of cytosolic potassium. The other conformer conducts extracellular calcium ions across cytoplasmic membrane of cells, relocates into lipid rafts, translocates the adenylate cyclase enzyme (AC) domain into cells and converts cytosolic ATP to cAMP. We show that the calcium-conducting activity of CyaA controls the path and kinetics of endocytic removal of toxin pores from phagocyte membrane. The enzymatically inactive but calcium-conducting CyaA-AC⁻ toxoid was endocytosed via a clathrin-dependent pathway. In contrast, a doubly mutated (E570K+E581P) toxoid, unable to conduct Ca²⁺ into cells, was rapidly internalized by membrane macropinocytosis, unless rescued by Ca²⁺ influx promoted in trans by ionomycin or intact toxoid. Moreover, a fully pore-forming CyaA-ΔAC hemolysin failed to permeabilize phagocytes, unless endocytic removal of its pores from cell membrane was decelerated through Ca²⁺ influx promoted by molecules locked in a Ca²⁺-conducting conformation by the 3D1 antibody. Inhibition of endocytosis also enabled the native B. pertussis-produced CyaA to induce lysis of J774A.1 macrophages at concentrations starting from 100 ng/ml. Hence, by mediating calcium influx into cells, the translocating conformer of CyaA controls the removal of bystander toxin pores from phagocyte membrane. This triggers a positive feedback loop of exacerbated cell permeabilization, where the efflux of cellular potassium yields further decreased toxin pore removal from cell membrane and this further enhances cell permeabilization and potassium efflux.     

Multiple advantageous amino acid variants in the NAT2 gene in human populations

Background

Genetic variation at NAT2 has been long recognized as the cause of differential ability to metabolize a wide variety of drugs of therapeutic use. Here, we explore the pattern of genetic variation in 12 human populations that significantly extend the geographic range and resolution of previous surveys, to test the hypothesis that different dietary regimens and lifestyles may explain inter-population differences in NAT2 variation.

Methodology/Principal Findings

The entire coding region was resequenced in 98 subjects and six polymorphic positions were genotyped in 150 additional subjects. A single previously undescribed variant was found (34T>C; 12Y>H). Several aspects of the data do not fit the expectations of a neutral model, as assessed by coalescent simulations. Tajima''s D is positive in all populations, indicating an excess of intermediate alleles. The level of between-population differentiation is low, and is mainly accounted for by the proportion of fast vs. slow acetylators. However, haplotype frequencies significantly differ across groups of populations with different subsistence.

Conclusions/Significance

Data on the structure of haplotypes and their frequencies are compatible with a model in which slow-causing variants were present in widely dispersed populations before major shifts to pastoralism and/or agriculture. In this model, slow-causing mutations gained a selective advantage in populations shifting from hunting-gathering to pastoralism/agriculture. We suggest the diminished dietary availability of folates resulting from the nutritional shift, as the possible cause of the fitness increase associated to haplotypes carrying mutations that reduce enzymatic activity.     

Sucking and allosucking duration in farmed red deer (Cervus elaphus)

Sucking duration in ungulates does not only mean milk transfer, but is also associated with maternal care in general. It seems to be a reflection of offspring demand rather than solely milk transfer rate. Thus, the objective of this study was to discriminate between sucking and allosucking (i.e. sucking non-maternal hind) behaviour in red deer according to the sucking duration.We hypothesized that: (1) calves should suck longer from their mothers than allosuck from non-maternal hinds; (2) sucking duration of calves frequently nursed by a particular non-maternal hind should be longer than that of calves occasionally allonursed; (3) sucking duration should be longer for bouts including one calf than two or more calves sucking simultaneously; (4) male calves should suck and allosuck longer than female calves; and (5) primiparous hinds should nurse and allonurse longer than multiparous hinds. We observed sucking behaviour of 25 hinds and their 38 calves (from birth until the youngest calf reached one month of age) in two seasons. We recorded 1730 sucking bouts, of which 11.62% in the first season and 4.37% in the second season were non-filial. The duration of filial sucking was significantly longer than non-filial sucking. A large individual variance in the incidence of non-filial sucking in both the calves and hinds was found. Therefore, the non-filial hind–calf pairs were categorized in two clusters according to the frequency of nursing non-filial calves for one hind in relationship to all nursing events for this hind by a cluster analysis (PROC CLUSTER, SAS). We used a general linear mixed model, GLMM (PROC MIXED, SAS) to test the influence of hind relationship to the nursed calf (filial, frequently allosucking non-filial, or occasionally allosucking non-filial pair). Sucking duration of occasionally allosucking non-filial calves was only marginally different from that of filial calves. There was no difference between the two groups of non-filial calves. Multiple sucking bouts were shorter than those with one calf. Male calves sucked longer than female calves; however, the greatest difference was recorded between frequently allosucking non-filial pairs of both sexes. Frequently allosucking non-filial males sucked the longest and differently from occasionally allosucking non-filial males. Frequently allosucking non-filial females sucked the shortest and differently from filial calves of both sexes. It is more likely that allosucking seems to be more important for male rather than female calves.Therefore, it is concluded that allosucking calves differ in their sucking behaviour and two types of allosuckers (frequent and occasional) should be taken into account when analyzing allosuckling behaviour.     

Repeated intraspecific divergence in life span and aging of African annual fishes along an aridity gradient

Life span and aging are substantially modified by natural selection. Across species, higher extrinsic (environmentally related) mortality (and hence shorter life expectancy) selects for the evolution of more rapid aging. However, among populations within species, high extrinsic mortality can lead to extended life span and slower aging as a consequence of condition‐dependent survival. Using within‐species contrasts of eight natural populations of Nothobranchius fishes in common garden experiments, we demonstrate that populations originating from dry regions (with short life expectancy) had shorter intrinsic life spans and a greater increase in mortality with age, more pronounced cellular and physiological deterioration (oxidative damage, tumor load), and a faster decline in fertility than populations from wetter regions. This parallel intraspecific divergence in life span and aging was not associated with divergence in early life history (rapid growth, maturation) or pace‐of‐life syndrome (high metabolic rates, active behavior). Variability across four study species suggests that a combination of different aging and life‐history traits conformed with or contradicted the predictions for each species. These findings demonstrate that variation in life span and functional decline among natural populations are linked, genetically underpinned, and can evolve relatively rapidly.     

Micronucleus frequency and content in healthy relatives of cancer patients

Objective: To compare chromosomal damage in lymphocytes of individuals who did or did not report first-degree relatives with cancer.

Materials and methods: Cases and controls (68 each) were matched for sex, age and radon exposure. Chromosomal damage was quantified as frequency of micronucleus-containing cells and proportion of centromere-free micronuclei.

Results: Individuals not reporting cancer in their families showed lower values of both the frequency of micronucleus-containing cells (n.s.) and the proportion of centromere-free micronuclei (p?<?0.05) in some subgroups, but not in all.

Conclusion: The chromosomal damage observed may be due to inheritable genomic instability, but environmental influences cannot be excluded.