Health applications of bioactive compounds from marine microalgae

Marine microalgae and cyanobacteria are very rich in several chemical compounds and, therefore, they may be used in several biological applications related with health benefits, among others. This review brings the research up-to-date on the bioactive compounds produced by marine unicellular algae, directly or indirectly related to human health. It covers and goes through the most studied applications of substances such as PUFA, sterols, proteins and enzymes, vitamins and pigments, in areas so diverse as human and animal nutrition, therapeutics, and aquaculture. The great potential of marine microalgae and the biocoumpounds they produce are discussed in this review.     

Larval life history and anti-predator strategies are affected by breeding phenology in an amphibian

Seasonal time constraints can pose strong selection on life histories. Time-constrained animals should prioritise fast development over predation risk to avoid unfavourable growing conditions. However, changes in phenology could alter the balance between anti-predator and developmental needs. We studied variation of anti-predator strategies in common frog (Rana temporaria) tadpoles in four populations from the two extremes of a latitudinal gradient across Sweden. We examined, under common conditions in the laboratory, the anti-predator responses and life histories of tadpoles raised with predatory Aeshna dragonfly larvae in two consecutive years with a difference of 20 days in breeding time in the north, but no difference in breeding time in the nouth. In a year with late breeding, northern tadpoles did not modify their behaviour and morphology in the presence of predators, and metamorphosed faster and smaller than tadpoles born in a year with early breeding. In the year with early breeding, northern tadpoles showed a completely different anti-predator strategy by reducing activity and developing morphological defences in the presence of predators. We discuss the possible mechanisms that could activate these responses (likely a form of environmentally-mediated parental effect). To our knowledge, this is the first study to show that a vertebrate modifies the anti-predator strategy of its offspring in response to natural variation in reproductive phenology, which highlights the need to consider phenology in studies of life-history evolution.     

Novel model for “calcium paradox” in sympathetic transmission of smooth muscles: Role of cyclic AMP pathway

It is well established that reduction of Ca²⁺ influx through L-type voltage-dependent Ca²⁺ channel (L-type VDCC), or increase of cytosolic cAMP concentration ([cAMP]c), inhibit contractile activity of smooth muscles in response to transmitters released from sympathetic nerves. Surprisingly, in this work we observed that simultaneous administration of L-type VDCC blocker (verapamil) and [cAMP]c enhancers (rolipram, IBMX and forskolin) potentiated purinergic contractions evoked by electrical field stimulation of rat vas deferens, instead of inhibiting them. These results, including its role in sympathetic transmission, can be considered as a “calcium paradox”. On the other hand, this potentiation was prevented by reduction of [cAMP]c by inhibition of adenylyl cyclase (SQ 22536) or depletion of Ca²⁺ storage of sarco-endoplasmic reticulum by blockade of Ca²⁺ reuptake (thapsigargin). In addition, cytosolic Ca²⁺ concentration ([Ca²⁺]_c) evaluated by fluorescence microscopy in rat adrenal medullary slices was significantly reduced by verapamil or rolipram. In contrast, simultaneous incubation of adrenal slices with these compounds significantly increased [Ca²⁺]_c. This effect was prevented by thapsigargin. Thus, a reduction of [Ca²⁺]_c due to blockade of Ca²⁺ influx through L-type VDCC could stimulate adenylyl cyclase activity increasing [cAMP]c thereby stimulating Ca²⁺ release from endoplasmic reticulum, resulting in augmented transmitter release in sympathetic nerves and contraction.     

A Metabolomics-driven Elucidation of the Anti-obesity Mechanisms of Xanthohumol

Mild, mitochondrial uncoupling increases energy expenditure and can reduce the generation of reactive oxygen species (ROS). Activation of cellular, adaptive stress response pathways can result in an enhanced capacity to reduce oxidative damage. Together, these strategies target energy imbalance and oxidative stress, both underlying factors of obesity and related conditions such as type 2 diabetes. Here we describe a metabolomics-driven effort to uncover the anti-obesity mechanism(s) of xanthohumol (XN), a prenylated flavonoid from hops. Metabolomics analysis of fasting plasma from obese, Zucker rats treated with XN revealed decreases in products of dysfunctional fatty acid oxidation and ROS, prompting us to explore the effects of XN on muscle cell bioenergetics. At low micromolar concentrations, XN acutely increased uncoupled respiration in several different cell types, including myocytes. Tetrahydroxanthohumol also increased respiration, suggesting electrophilicity did not play a role. At higher concentrations, XN inhibited respiration in a ROS-dependent manner. In myocytes, time course metabolomics revealed acute activation of glutathione recycling and long term induction of glutathione synthesis as well as several other changes indicative of short term elevated cellular stress and a concerted adaptive response. Based on these findings, we hypothesize that XN may ameliorate metabolic syndrome, at least in part, through mitochondrial uncoupling and stress response induction. In addition, time course metabolomics appears to be an effective strategy for uncovering metabolic events that occur during a stress response.     

Adaptation of the 3H-Leucine Incorporation Technique to Measure Heterotrophic Activity Associated with Biofilm on the Blades of the Seaweed Sargassum spp.

The ecological interaction between microorganisms and seaweeds depends on the production of secondary compounds that can influence microbial diversity in the water column and the composition of reef environments. We adapted the ³H-leucine incorporation technique to measure bacterial activity in biofilms associated with the blades of the macroalgae Sargassum spp. We evaluated (1) if the epiphytic bacteria on the blades were more active in detritus or in the biofilm, (2) substrate saturation and linearity of ³H-leucine incorporation, (3) the influence of specific metabolic inhibitors during ³H-leucine incorporation under the presence or absence of natural and artificial light, and (4) the efficiency of radiolabeled protein extraction. Scanning electron microscopy showed heterogeneous distribution of bacteria, diatoms, and polymeric extracellular secretions. Active bacteria were present in both biofilm and detritus on the blades. The highest ³H-leucine incorporation was obtained when incubating blades not colonized by macroepibionts. Incubations done under field conditions reported higher ³H-leucine incorporation than in the laboratory. Light quality and sampling manipulation seemed to be the main factors behind this difference. The use of specific metabolic inhibitors confirmed that bacteria are the main group incorporating ³H-leucine but their association with primary production suggested a symbiotic relationship between bacteria, diatoms, and the seaweed.     

Cytogenetic diversity of SSR motifs within and between Hordeum species carrying the H genome: H. vulgare L. and H. bulbosum L.

Non-denaturing FISH (ND-FISH) was used to compare the distribution of four simple sequence repeats (SSRs)—(AG) _n , (AAG) _n , (ACT) _n and (ATC) _n —in somatic root tip metaphase spreads of 12 barley (H. vulgare ssp. vulgare) cultivars, seven lines of their wild progenitor H. vulgare ssp. spontaneum, and four lines of their close relative H. bulbosum, to determine whether the range of molecular diversity shown by these highly polymorphic sequences is reflected at the chromosome level. In both, the cultivated and wild barleys, clusters of AG and ATC repeats were invariant. In contrast, clusters of AAG and ACT showed polymorphism. Karyotypes were prepared after the identification of their seven pairs of homologous chromosomes. Variation between these homologues was only observed in one wild accession that showed the segregation of a reciprocal translocation involving chromosomes 5H and 7H. The two subspecies of H. vulgare analysed were no different in terms of their SSRs. Only AAG repeats were found clustered strongly on the chromosomes of all lines of H. bulbosum examined. Wide variation was seen between homologous chromosomes within and across these lines. These results are the first to provide insight into the cytogenetic diversity of SSRs in barley and its closest relatives. Differences in the abundance and distribution of each SSR analysed, between H. vulgare and H. bulbosum, suggest that these species do not share the same H genome, and support the idea that these species are not very closely related. Southern blotting experiments revealed the complex organization of these SSRs, supporting the findings made with ND-FISH.     

Entrainment of shovelnose sturgeon by towboat navigation in the Upper Mississippi River

Estimated number of shovelnose sturgeon Scaphirhynchus platorynchus impacted annually by towboat entrainment in navigation pools of the Upper Mississippi River were compared against estimates of fishery harvest and ambient population densities to evaluate the relevance of entrainment at the population level. Mean number of sturgeon entrained per kilometer of navigation was estimated at 0.02, and mean number entrained annually considering towboat traffic was estimated at 0.38 sturgeon/ha. Losses associated with entrainment were mostly lower than fishery harvest, although differences were not large. The two sources of mortality combined could potentially reduce the mature adult population to a level where it no longer has the reproductive capacity to replenish itself. Thus, through a combination of entrainment and fishing mortality shovelnose sturgeon may be looming near unsustainable population levels. These estimates are preliminary considering the many uncertainties associated with quantifying entrainment and its effects. Additional research is needed not only to derive better estimates, but also to develop options for managing entrainment.     

Mathematical Modeling of Respiratory System Mechanics in the Newborn Lamb

In this paper, a mathematical model of the respiratory mechanics is used to reproduce experimental signal waveforms acquired from three newborn lambs. As the main challenge is to determine specific lamb parameters, a sensitivity analysis has been realized to find the most influent parameters, which are identified using an evolutionary algorithm. Results show a close match between experimental and simulated pressure and flow waveforms obtained during spontaneous ventilation and pleural pressure variations acquired during the application of positive pressure, since root mean square errors equal to 0.0119, 0.0052 and 0.0094. The identified parameters were discussed in light of previous knowledge of respiratory mechanics in the newborn.     

Pollen consumed by the solitary bee Tetrapedia diversipes (Apidae: Tetrapediini) in a tropical agroecosystem

Pollen analysis of the larval food supply is an important tool for identifying the plants that provide the floral resources used by bees. The present study documents the pollen sources consumed by larvae of the solitary bee Tetrapedia diversipes in a tropical agroecosystem. A total of 60 pollen types were recorded with three families being the most important. Euphorbiaceae (60.5%), Malpighiaceae (16.8%) and Asteraceae (12.2%) pollen had the greatest representation in the samples examined. The pollen of Dalechampia dioscoreifolia predominated in the diet of the larvae of T. diversipes (RF?=?56.35%) and indicates the importance of this plant in maintaining populations of this solitary bee.     

Cyanobacterial dominance in Brazil: distribution and environmental preferences

Based on a literature survey, we evaluated the periods of cyanobacterial dominance in Brazil. We hypothesized that variability of environmental forces along the country will promote or facilitate temporal and spatial mosaic in cyanobacterial dominance. The most striking outcomes are related to the dominance of Cylindrospermopsis, Dolichospermum, and Microcystis. Although they share important adaptive strategies (e.g., aerotopes, large size and toxins production), our findings suggest that they have different environmental preferences. Dolichospermum and Microcystis dominated mainly in warm-rainy periods whereas Cylindrospermopsis was more common during dry periods and in mixed systems, or formed perennial dominance. Maximum phosphorus concentrations were observed in reservoirs dominated by Cylindrospermopsis. Although the main genera reached high biomass levels individually, different abilities to form dominance and co-dominance were observed. The number of co-dominance of Chroococales and Nostocales was almost the same as the individual occurrence of the main genera from these groups. This dataset reveals patterns of dominance of these cyanobacteria and also indicates that physiological features will cause differences in the mechanisms of interactions between species. The understanding of these processes and their relationship to environmental conditions will promote better understanding of cyanobacterial dominance and increase our ability to predict and manage these events.