Seed dispersal by carnivores in temperate and tropical dry forests

The seed dispersal mechanisms and regeneration of various forest ecosystems can benefit from the actions of carnivores via endozoochory. This study was aimed to evaluate the role of carnivores in endozoochory and diploendozoochory, as well as their effect on seed viability, scarification, and germination in two forest ecosystems: temperate and tropical dry forest. We collected carnivore scat in the Protected Natural Area of Sierra Fría in Aguascalientes, Mexico, for 2 years to determine the abundance and richness of seeds dispersed by each carnivore species, through scat analysis. We assessed seed viability through optical densitometry using X‐rays, analyzed seed scarification by measuring seed coat thickness using a scanning electron microscope, and evaluated seed germination in an experiment as the percentage of seeds germinated per carnivore disperser, plant species, and forest type. In the temperate forest, four plant species (but mainly Arctostaphylos pungens) were dispersed by four mammal species. The gray fox dispersed the highest average number of seeds per scat (66.8 seeds). Bobcat dispersed seeds through diploendozoochory, which was inferred from rabbit (Sylvilagus floridanus) hair detected in their scats. The tropical dry forest presented higher abundance of seeds and richness of dispersed plant species (four species) than in the temperate forest, and the coati dispersed the highest number of seeds (8,639 seeds). Endozoochory and diploendozoochory did not affect viability in thick‐testa seeds (1,480 µm) in temperate forest and thin‐testa seeds (281 µm) in tropical dry forest. Endozoochory improved the selective germination of seeds. Nine plant species were dispersed by endozoochory, but only one species (Juniperus sp.) by diploendozoochory. These results suggest that carnivores can perform an important ecological function by dispersing a great abundance of seeds, scarifying these seeds causing the formation of holes and cracks in the testas without affecting viability, and promoting the selective germination of seeds.     

Rosmarinic acid improves function and in vitro fertilising ability of boar sperm after cryopreservation

During cryopreservation, oxidative stress exerts physical and chemical changes on sperm functionality. In the present study we investigated the antioxidant effect of rosmarinic acid (RA) on quality and fertilising ability of frozen–thawed boar spermatozoa. Ejaculates collected from mature boar were cryopreserved in lactose–egg yolk buffer supplemented with different concentrations of RA (0 μM, 26.25 μM, 52.5 μM and 105 μM). Motion parameters, acrosome and plasma membrane integrity, lipoperoxidation levels, DNA oxidative damage (8-hydroxy-2-deoxyguanosine base lesion) and in vitro fertilisation ability were evaluated. Total and progressive motility were significantly higher in experimental extenders with RA than in the control (P < 0.05) at 0 and 120 min post-thawing. The plasma and acrosomal membrane integrity were improved by supplementation with 105 μM RA (P < 0.05). Negative correlation between RA and malondialdehyde (MDA) concentration were determined (P < 0.05). After thawing, the percentage of spermatozoa with oxidised DNA did not differ between extenders, however, at 120 and 240 min post-thawing, the samples supplemented with 105 μM RA showed the lowest DNA oxidation rate (P < 0.05). The penetration rate was significantly higher on spermatozoa cryopreserved with 105 μM RA (P < 0.05). The results suggest that RA provides a protection for boar spermatozoa against oxidative stress during cryopreservation by their antioxidant properties.     

Differential usage of alternative pathways of double-strand break repair in Drosophila

Double-strand DNA breaks can be repaired by any of several alternative mechanisms that differ greatly in the nature of the final repaired products. We used a reporter construct, designated "Repair reporter 3" (Rr3), to measure the relative usage of these pathways in Drosophila germ cells. The method works by creating a double-strand break at a specific location such that expression of the red fluorescent protein, DsRed, in the next generation can be used to infer the frequency at which each pathway was used. A key feature of this approach is that most data come from phenotypic scoring, thus allowing large sample sizes and considerable precision in measurements. Specifically, we measured the proportion of breaks repaired by (1) conversion repair, (2) nonhomologous end joining (NHEJ), or (3) single-strand annealing (SSA). For conversion repair, the frequency of mitotic crossing over in the germ line indicates the relative prevalence of repair by double Holliday junction (DHJ) formation vs. the synthesis-dependent strand annealing (SDSA) pathway. We used this method to show that breaks occurring early in germ-line development were much more frequently repaired via single-strand annealing and much less likely to be repaired by end joining compared with identical breaks occurring later in development. Conversion repair was relatively rare when breaks were made either very early or very late in development, but was much more frequent in between. Significantly, the changes in relative usage occurred in a compensatory fashion, such that an increase in one pathway was accompanied by decreases in others. This negative correlation is interpreted to mean that the pathways for double-strand break repair compete with each other to handle a given breakage event.     

Membrane bioreactor wastewater treatment plants reveal diverse yeast and protist communities of potential significance in biofouling

The yeast community was studied in a municipal full-scale membrane bioreactor wastewater treatment plant (MBR-WWTP). The unexpectedly high diversity of yeasts indicated that the activated sludge formed a suitable environment for them to proliferate, with cellular concentrations of 2.2 ± 0.8?×?10³ CFU ml^?1. Sixteen species of seven genera were present in the biological reactor, with Ascomycetes being the most prevalent group (93%). Most isolates were able to grow in a synthetic wastewater medium, adhere to polyethylene surfaces, and develop biofilms of variable complexity. The relationship between yeast populations and the protists in the MBR-WWTP was also studied, revealing that some protist species preyed on and ingested yeasts. These results suggest that yeast populations may play a role in the food web of a WWTP and, to some extent, contribute to membrane biofouling in MBR systems.     

Regulation of progesterone receptor isoforms content in human astrocytoma cell lines

Progesterone regulates several functions through the interaction with its intracellular receptor (PR) which expresses two isoforms with different functions and regulation: PR-A and PR-B. Both PR isoforms have been detected in human astrocytomas, the most common and aggressive primary brain tumours, but their regulation and function are unknown. We studied the effects of estradiol, progesterone and their receptor antagonists (ICI 182,780 and RU 486) on PR isoforms content in U373 and D54 human astrocytoma cell lines, respectively derived from grades III and IV astrocytomas, by Western blot analysis. In U373 cells we also evaluated the effects of PR-A overexpression on cell growth. We observed that in U373 cells estradiol increased the content of both PR isoforms whereas in D54 cells it had no effects. Estradiol effects were blocked by ICI 182,780. In both cell lines, PR isoforms content was down-regulated by progesterone after estradiol treatment. This effect was blocked by RU 486. We observed that overexpression of PR-A significantly diminished the increase in U373 cells number produced after progesterone treatment. Our results suggest a differential PR isoforms regulation depending on the evolution grade of human astrocytoma cells, and an inhibitory role of PR-A on progesterone effects on astrocytomas cell growth.     

Use of a Chagas Urine Nanoparticle Test (Chunap) to Correlate with Parasitemia Levels in T. cruzi/HIV Co-infected Patients

Background

Early diagnosis of reactivated Chagas disease in HIV patients could be lifesaving. In Latin America, the diagnosis is made by microscopical detection of the T. cruzi parasite in the blood; a diagnostic test that lacks sensitivity. This study evaluates if levels of T. cruzi antigens in urine, determined by Chunap (Chagas urine nanoparticle test), are correlated with parasitemia levels in T. cruzi/HIV co-infected patients.

Methodology/Principal Findings

T. cruzi antigens in urine of HIV patients (N = 55: 31 T. cruzi infected and 24 T. cruzi serology negative) were concentrated using hydrogel particles and quantified by Western Blot and a calibration curve. Reactivation of Chagas disease was defined by the observation of parasites in blood by microscopy. Parasitemia levels in patients with serology positive for Chagas disease were classified as follows: High parasitemia or reactivation of Chagas disease (detectable parasitemia by microscopy), moderate parasitemia (undetectable by microscopy but detectable by qPCR), and negative parasitemia (undetectable by microscopy and qPCR). The percentage of positive results detected by Chunap was: 100% (7/7) in cases of reactivation, 91.7% (11/12) in cases of moderate parasitemia, and 41.7% (5/12) in cases of negative parasitemia. Chunap specificity was found to be 91.7%. Linear regression analysis demonstrated a direct relationship between parasitemia levels and urine T. cruzi antigen concentrations (p<0.001). A cut-off of > 105 pg was chosen to determine patients with reactivation of Chagas disease (7/7). Antigenuria levels were 36.08 times (95% CI: 7.28 to 64.88) higher in patients with CD4+ lymphocyte counts below 200/mL (p = 0.016). No significant differences were found in HIV loads and CD8+ lymphocyte counts.

Conclusion

Chunap shows potential for early detection of Chagas reactivation. With appropriate adaptation, this diagnostic test can be used to monitor Chagas disease status in T. cruzi/HIV co-infected patients.     

Modified basal elements in Dicroidium fronds (Corystospermales)

We describe a distinct type of heteromorphic basal frond element in four species of the seed-fern foliage Dicroidium, based principally on a survey of plant-fossil collections from the Triassic of Antarctica. The modified foliar elements are conspicuously enlarged, and arise at wide angles and obliquely to the frond plane. Those of D. elongatum and D. crassinerve arise more or less directly from the petiole base; they are overall wedge- to fan-shaped with variably dissected margins and fan-shaped venation. Those of D. odontopteroides and D. dubium are (sub)circular, reniform, or obcordate, also with fan-shaped venation, or divided into narrow tongue-shaped segments with alethopteroid venation. The basal elements of some species commonly occur isolated. By analogy with comparable structures among other plant groups, we conclude that the basal elements represent a distinct, early leaf-ontogenetic architectural unit in the frond bauplan of Dicroidium, which provides an important additional character for a more accurate delimitation and systematic classification. Similar structures also occur on the corystosperm reproductive organs Umkomasia and Pteruchus. It appears that the basal elements were particularly common among high-latitude Dicroidium trees that flourished in a strongly seasonal light regime. We hypothesize that the modified elements may represent the initial foliar outgrowths during spring flush, ensuring a rapid re-initiation of sap flow and metabolic activity after the extended period of winter dormancy.     

Exploring polymorphisms in B-DNA helical conformations

The traditional mesoscopic paradigm represents DNA as a series of base-pair steps whose energy response to equilibrium perturbations is elastic, with harmonic oscillations (defining local stiffness) around a single equilibrium conformation. In addition, base sequence effects are often analysed as a succession of independent XpY base-pair steps (i.e. a nearest-neighbour (NN) model with only 10 unique cases). Unfortunately, recent massive simulations carried out by the ABC consortium suggest that the real picture of DNA flexibility may be much more complex. The paradigm of DNA flexibility therefore needs to be revisited. In this article, we explore in detail one of the most obvious violations of the elastic NN model of flexibility: the bimodal distributions of some helical parameters. We perform here an in-depth statistical analysis of a very large set of MD trajectories and also of experimental structures, which lead to very solid evidence of bimodality. We then suggest ways to improve mesoscopic models to account for this deviation from the elastic regime.