Variability,function and phylogenetic significance of periostracal microprojections in unionoid bivalves (Mollusca)

Microprojections of unionoid shells are virtually unstudied but could be important characters for resolving questions on the phylogeny and ecology of these bivalves. By investigating 26 unionoid and three species of their closest living relatives, the Trigonioida, using scanning electron microscopy, we identified three types of periostracal microprojections. (1) Microridges were present only in one species from each of the two unionoid families Mycetopodidae (Anodontites trapesialis) and Iridinidae (Chambardia bourguignati) and may represent a synapomorphy for the mycetopodid‐iridinid clade. In A. trapesialis, microridges were additionally equipped with (2)ensp;flag‐like projections (microfringes), possibly a synapomorphic character for the Mycetopodidae. Examination of partially bleached specimens indicated that both microridges and microfringes are predominantly or purely organic. In contrast, previously undescribed (3) spicule‐like spikes represent calcifications within the periostracum. These were found in 20 of the 29 species and four of the six unionoid families. Spikes were particularly large and abundant in umbonal (juvenile) shell regions and species characteristic of fast‐flowing habitats. These structures may thus serve in protecting the periostracum and shell underneath, and/or stabilizing life position by increasing shell friction. Microfringes and microridges, on the other hand, possibly aid in the orientation of the mussel within the sediment.     

Similar Intracellular Location and Stimulus Reactivity,but Differential Mobility of Tailless (Vicia faba) and Tailed Forisomes (Phaseolus vulgaris) in Intact Sieve Tubes

Sieve elements of legumes contain forisomes—fusiform protein bodies that are responsible for sieve-tube occlusion in response to damage or wound signals. Earlier work described the existence of tailless and tailed forisomes. This study intended to quantify and compare location and position of tailless (in Vicia faba) and tailed (in Phaseolus vulgaris) forisomes inside sieve elements and to assess their reactivity and potential mobility in response to a remote stimulus. Location (distribution within sieve elements) and position (forisome tip contacts) of more than altogether 2000 forisomes were screened in 500 intact plants by laser scanning confocal microscopy in the transmission mode. Furthermore, we studied the dispersion of forisomes at different locations in different positions and their positional behaviour in response to distant heat shocks. Forisome distribution turned out to be species-specific, whereas forisome positions at various locations were largely similar in bushbean (Phaseolus) and broadbean (Vicia). In general, the tailless forisomes had higher dispersion rates in response to heat shocks than the tailed forisomes and forisomes at the downstream (basal) end dispersed more frequently than those at the upstream end (apical). In contrast to the tailless forisomes that only oscillate in response to heat shocks, downstream-located tailed forisomes can cover considerable distances within sieve elements. This displacement was prevented by gentle rubbing of the leaf (priming) before the heat shock. Movement of these forisomes was also prohibited by Latrunculin A, an inhibitor of actin polymerization. The apparently active mobility of tailed forisomes gives credence to the idea that at least the latter forisomes are not free-floating, but connected to other sieve-element structures.     

Comparison of the Cecal Microbiota of Domestic and Wild Turkeys

The extent to which production methods alter intestinal microbial communities of livestock is currently unknown. As the intestinal microbiota may affect animal health, nutrition, and food safety, a baseline comparison of the cecal communities of domestic and wild turkeys was performed. Oligonucleotide fingerprinting of ribosomal RNA (rRNA) genes (OFRG) of 2,990 16S rRNA clones and dot blot quantification of dominant populations were used to identify the dominant bacterial taxa. Seventy-three percent of all the clones belonged to as yet uncultured genera. However, at a higher phylogenetic level, the OFRG library was composed of 54% Bacteroidetes clones (52% of the domestic library clones, 56% of the wild library clones), 30% Firmicutes clones (33% of the domestic library clones, 32% of the wild library clones), 3% Proteobacteria clones (5% domestic, 2% wild), and 3% Deferribacteres clones (4% domestic, 1% wild). Seven percent of the clones were unidentifiable (6% domestic, 9% wild). Bacteroidetes clones included the genera Alistipes, Prevotella, Megamonas, and Bacteroides. Of the Clostridiales clones, groups IV, IX, and XIV including genera Faecalibacterium, Megasphaera, Phascolarctobacterium, and Papillibacter were predominant. Lactobacillus, Enterococcus, and Streptococcus bacilli were also identified. beta- delta- and gamma-proteobacterial genera included Acinetobacter, Sutterella, and Escherichia. Deferribacteres clones showed high similarity to Mucispirillum schaedleri. Statistical comparison of the domestic and wild turkey clone libraries indicated similar levels of community richness and evenness despite the fact that the two libraries shared only 30% of the total clone operational taxonomic units. Together these results indicate that although high level taxonomic community structure is similar, high-density turkey production causes considerable divergence of the genera found in the ceca of commercial birds from those of their wild counterparts.     

Mnl2, a novel component of the ER associated protein degradation pathway

In eukaryotes, membrane and soluble proteins of the secretory pathway enter the endoplasmic reticulum (ER) after synthesis in an unfolded state. Directly after entry, most proteins are modified with glycans at suitable glycosylation sites and start to fold. A protein that cannot fold properly will be degraded in a process called ER associated degradation (ERAD). Failures in ERAD, either by loss of function or by premature degradation of proteins, are a cause of severe diseases. Therefore, the search for novel ERAD components to gain better insight in this process is of high importance. Carbohydrate trimming is a relevant process in ER quality control. In this work a novel putative yeast mannosidase encoded by the open reading frame YLR057W was identified and named Mnl2. Deletion of MNL2 diminished the degradation efficiency of misfolded CPY^* in the absence of the cognate mannosidase Mnl1, indicating a specific role in ERAD.     

Characterization of enhanced monovalent and bivalent thrombin DNA aptamer binding using single molecule force spectroscopy

Thrombin aptamer binding strength and stability is dependent on sterical parameters when used for atomic force microscopy sensing applications. Sterical improvements on the linker chemistry were developed for high-affinity binding. For this we applied single molecule force spectroscopy using two enhanced biotinylated thrombin aptamers, BFF and BFA immobilized on the atomic force microscopy tip via streptavidin. BFF is a dimer composed of two single-stranded aptamers (aptabody) connected to each other by a complementary sequence close to the biotinylated end. In contrast, BFA consists of a single DNA strand and a complementary strand in the supporting biotinylated part. By varying the pulling velocity in force-distance cycles the formed thrombin-aptamer complexes were ruptured at different force loadings allowing determination of the energy landscape. As a result, BFA aptamer showed a higher binding force at the investigated loading rates and a significantly lower dissociation rate constant, k_off, compared to BFF. Moreover, the potential of the aptabody BFF to form a bivalent complex could clearly be demonstrated.     

Anti-retroviral treatment outcomes among older adults in Zomba district, Malawi

Background

There are approximately 3 million people aged 50 and older in sub-Saharan Africa who are HIV-positive. Despite this, little is known about the characteristics of older adults who are on treatment and their treatment outcomes.

Methods

A retrospective cohort analysis was performed using routinely collected data with Malawi Ministry of Health monitoring tools from facilities providing antiretroviral therapy services in Zomba district. Patients aged 25 years and older initiated on treatment from July 2005 to June 2010 were included. Differences in survival, by age group, were determined using Kaplan–Meier survival plots and Cox proportional hazards regression models.

Results

There were 10,888 patients aged 25 and older. Patients aged 50 and older (N = 1419) were more likely to be male (P<0.0001) and located in rural areas (P = 0.003) than those aged 25–49. Crude survival estimates among those aged 50–59 were not statistically different from those aged 25–49 (P = 0.925). However, survival among those aged 60 and older (N = 345) was worse (P = 0.019) than among those 25–59. In the proportional hazards model, after controlling for sex and stage at initiation, survival in those aged 50–59 did not differ significantly from those aged 25–49 (hazard ratio 1.00 (95% CI: 0.79 to 1.27; P = 0.998) but the hazard ratio was 1.46 (95% CI: 1.03 to 2.06; P = 0.032) for those aged 60 and older compared to those aged 25–49.

Conclusions

Treatment outcomes of those aged 50–59 are similar to those aged 25–49. A better understanding of how older adults present for and respond to treatment is critical to improving HIV services.     

Mitochondrial haplogroups, control region polymorphisms and malignant melanoma: a study in middle European Caucasians

Background

Because mitochondria play an essential role in energy metabolism, generation of reactive oxygen species (ROS), and apoptosis, sequence variation in the mitochondrial genome has been postulated to be a contributing factor to the etiology of multifactorial age-related diseases, including cancer. The aim of the present study was to compare the frequencies of mitochondrial DNA (mtDNA) haplogroups as well as control region (CR) polymorphisms of patients with malignant melanoma (n = 351) versus those of healthy controls (n = 1598) in Middle Europe.

Methodology and Principal Findings

Using primer extension analysis and DNA sequencing, we identified all nine major European mitochondrial haplogroups and known CR polymorphisms. The frequencies of the major mitochondrial haplogroups did not differ significantly between patients and control subjects, whereas the frequencies of the one another linked CR polymorphisms A16183C, T16189C, C16192T, C16270T and T195C were significantly higher in patients with melanoma compared to the controls. Regarding clinical characteristics of the patient cohort, none of the nine major European haplogroups was associated with either Breslow thickness or distant metastasis. The CR polymorphisms A302CC-insertion and T310C-insertion were significantly associated with mean Breslow thickness, whereas the CR polymorphism T16519C was associated with metastasis.

Conclusions and Significance

Our results suggest that mtDNA variations could be involved in melanoma etiology and pathogenesis, although the functional consequence of CR polymorphisms remains to be elucidated.