Neo-tropical felid activity patterns in relation to potential prey and intraguild competitors in the Calakmul Biosphere Reserve,Mexico

Predator behaviors influence, and are influenced by, prey and competitor behaviors. Jaguars (Panthera onca), pumas (Puma concolor), and ocelots (Leopardus pardalis) coexist throughout their geographic range as the three largest predators in a multi-predator community across diverse environments. This study tested for non-random segregation and overlap in the activity patterns of these felids and their shared prey in the southern buffer zone of the Calakmul Biosphere Reserve, in southern Mexico, using camera traps during February to August 2019. We detected little temporal segregation between the nocturnal activities of jaguars, pumas, and ocelots, although pumas were more active closer to dawn. Jaguars had low activity overlap with species likely to be common prey, whereas ocelots had high overlap with their potential prey. Pumas displayed finer-scale similarities in activity with species likely to be common prey. In an understudied area of conservation importance, this study shows that temporal segregation is an unlikely mechanism of coexistence. Further research should incorporate spatio-temporal avoidance and dietary differences to improve our understanding of the mechanisms that drive coexistence between generalist species in a diverse assemblage of threatened felids. Abstract in Spanish is available with online material.     

Polymerization of τ into Filaments in the Presence of Heparin: The Minimal Sequence Required for τ - τ Interaction

Abstract: Paired helical filaments isolated from the brains of patients with Alzheimer's disease are composed of a major protein component, the microtubule-associated protein termed τ, together with other nonprotein components, including heparan, a glycosaminoglycan, the more extensively sulfated form of which is heparin. As some of these nonprotein components may modulate the assembly of τ into filamentous structures, we have analyzed the ability of the whole τ protein or some of its fragments to self-assemble in the presence of heparin. Different τ fragments, all of them containing some sequences of the tubulin-binding motif, can assemble in vitro into filaments. We have also found formation of polymers with the 18-residue-long peptide corresponding to the third tubulin-binding motif of τ. This suggests that the ability of τ for self-assembly could be localized in a short sequence of amino acids present in the tubulin-binding repeats of the τ molecule.     

Homothorax switches function of Drosophila photoreceptors from color to polarized light sensors

Different classes of photoreceptors (PRs) allow animals to perceive various types of visual information. In the Drosophila eye, the outer PRs of each ommatidium are involved in motion detection while the inner PRs mediate color vision. In addition, flies use a specialized class of inner PRs in the "dorsal rim area" of the eye (DRA) to detect the e-vector of polarized light, allowing them to exploit skylight polarization for orientation. We show that homothorax is both necessary and sufficient for inner PRs to adopt the polarization-sensitive DRA fate instead of the color-sensitive default state. Homothorax increases rhabdomere size and uncouples R7-R8 communication to allow both cells to express the same opsin rather than different ones as required for color vision. Homothorax expression is induced by the iroquois complex and the wingless (wg) pathway. However, crucial wg pathway components are not required, suggesting that additional signals are involved.     

Identification and characterization of vaccinia virus genes encoding proteins that are highly antigenic in animals and are immunodominant in vaccinated humans.

Vaccinia virus (VV) is a potent immunogen, but the nature of VV proteins involved in the activation of the immune response of the host is not yet known. By screening a lambda gt11 expression library of rabbitpox virus DNA with serum from humans vaccinated against smallpox or with serum from VV-immunized animals, we identified several VV genes that encode highly antigenic viral proteins with molecular masses of 62, 39, 32, 25, 21, and 14 kDa. It was found that VV proteins of 62, 39, 25, and 21 kDa are part of the virus core, while proteins of 32 and 14 kDa are part of the virus envelope. All of these proteins were synthesized at late times postinfection. Proteins of 62 and 25 kDa were produced by cleavage of larger precursors of 95 kDa (p4a) and 28 kDa, respectively. The 21-kDa protein was the result of a cleavage of p4a, presumably at amino acid Gly-697. DNA sequence analysis, in comparison with the known nucleotide sequence of VV, provided identification of the corresponding open reading frames. Expression of the viral genes in Escherichia coli was used to monitor which of the viral antigens elicit immunodominant responses and the location of antigenic domains. Three viral antigens of 62, 39, and 32 kDa exhibited immunodominant characteristics. The most antigenic sites of 62 and 39 kDa were identified at the N terminus (amino acids 132 to 295) and C terminus (last 103 amino acids), respectively. Immunization of mice with the 62-, 39-, or 14-kDa antigenic proteins conferred different degrees of protection from VV challenge. Proteins of 32 and 14 kDa induced cellular proliferative responses in VV-infected mice. Our findings demonstrate the nature of VV proteins involved in the activation of host immune responses after vaccination, provide identification of the viral gene locus, and define structural and immunological properties of these antigenic VV proteins.     

Steroid Hydroxylation by Basidiomycete Peroxygenases: a Combined Experimental and Computational Study

The goal of this study is the selective oxyfunctionalization of steroids under mild and environmentally friendly conditions using fungal enzymes. With this purpose, peroxygenases from three basidiomycete species were tested for the hydroxylation of a variety of steroidal compounds, using H₂O₂ as the only cosubstrate. Two of them are wild-type enzymes from Agrocybe aegerita and Marasmius rotula, and the third one is a recombinant enzyme from Coprinopsis cinerea. The enzymatic reactions on free and esterified sterols, steroid hydrocarbons, and ketones were monitored by gas chromatography, and the products were identified by mass spectrometry. Hydroxylation at the side chain over the steroidal rings was preferred, with the 25-hydroxyderivatives predominating. Interestingly, antiviral and other biological activities of 25-hydroxycholesterol have been reported recently (M. Blanc et al., Immunity 38:106–118, 2013, http://dx.doi.org/10.1016/j.immuni.2012.11.004). However, hydroxylation in the ring moiety and terminal hydroxylation at the side chain also was observed in some steroids, the former favored by the absence of oxygenated groups at C-3 and by the presence of conjugated double bonds in the rings. To understand the yield and selectivity differences between the different steroids, a computational study was performed using Protein Energy Landscape Exploration (PELE) software for dynamic ligand diffusion. These simulations showed that the active-site geometry and hydrophobicity favors the entrance of the steroid side chain, while the entrance of the ring is energetically penalized. Also, a direct correlation between the conversion rate and the side chain entrance ratio could be established that explains the various reaction yields observed.     

Identification of a unique gene cluster of Brucella spp. that mediates adhesion to host cells

Brucella, the causative agent of brucellosis, a major zoonotic disease affecting a broad range of mammals, is a gram-negative bacterium whose virulence is dependent on the capacity to attach and invade different cells of the host. The bacterium is able to infect through a diverse repertoire of epitheliums: skin, airways or gastric. Although much has been studied on the mechanisms Brucella uses to establish an intracellular replication niche, almost none is known on how the bacterium adheres and invades host cells. We report here the identification of a pathogenicity island that harbors a gene homologous to proteins with bacterial immunoglobulin-like domains present in other pathogens that play a role in attachment and invasion. Deletion of the entire island results in a mutant with a reduced attachment capacity measured by intracellular replication and adhesion assays. Intraperitoneal and oral experimental infection of mice strongly suggests that this island plays a role during the oral infection probably mediating attachment and trespassing of the gastric epithelium to establish a systemic infection.     

On-line monitoring of responses to nutrient feed additions by multi-frequency permittivity measurements in fed-batch cultivations of CHO cells

Changes in the nutrient availability of mammalian cell cultures are reflected in the β-dispersion parameter characteristic frequency (f _C ) and the on-line dual frequency permittivity signal. Multi-frequency permittivity measurements were therefore evaluated in fed-batch cultivations of two different CHO cell lines. Similar responses to nutrient depletions and discontinuous feed additions were monitored in different cultivation phases and experimental setups. Sudden increases in permittivity and f _C occurred when feed additions were conducted. A constant or declining permittivity value in combination with a decrease in f _C indicated nutrient limitations. f _C correlated well with changes in oxygen uptake rate when cell diameter remained constant, indicating that metabolic activity is reflected in the value of f _C . When significant cell size changes occurred during the cultivations, the analysis of the β-dispersion parameters was rendered complex. For the application of our findings in other systems it will be hence required to conduct additional off-line measurements. Based on these results, it is hypothesized that multi-frequency permittivity measurements can give information on the intracellular or physiological state in fed-batch mode. Similar observations were made when using different cell lines and feeding strategies, indicating that the findings are transferable to other cell lines and systems. The results should lead to an improved understanding of routine fed-batch processes. Additional studies are, however, required to explore how these observations can be used for fed-batch process development and optimization.     

Potentially handicapped but otherwise functional: Malformations in prey capture tools show no impacts on octopus life

Larval mortality is a keystone ecological factor for many benthic octopus since it mostly occurs before their settlement in the sea bottom as benthic juveniles. The literature had revealed that records of adult animals with morphological abnormalities (teratologies) are fewer in species with complex life cycle than in those with direct development. This is a direct consequence of the morphological, physiological, and development challenges that the transition from the larval to the adult morphology represents. During a routine fishing sample, we found an immature female horned octopus with additional buccal structures in two suckers of its ventral arms, likely rendering these suckers as inefficient. Based on the literature about the natural history of octopus, we provide evidence that these abnormalities were present at the moment of hatch. We evaluated the impact of the teratologies by comparing the shape of the buccal beaks and the trophic niche of the individual with five normal conspecifics. Although the beaks showed a different shape than normal individuals, the trophic niche was similar. Surprisingly, the teratological condition of the individual likely had no severe impacts on its life, even though it likely represents a handicap for its survival during its planktonic life. We also comment on other previous records from the literature of teratological adult octopus to highlight the amazing adaptive capacity of octopus to deal with challenging morphologies.     

Bone marrow stromal cells produce nerve growth factor and glial cell line-derived neurotrophic factors

Bone marrow stromal cells (BMSC) have attracted interest through their possible use for cell therapy in neurological diseases. Recent reports demonstrated that these cells are able to migrate and have potential for neuronal differentiation after transplantation into brain parenchyma. The objective of this work was determine whether rat BMSC express NGF and GDNF, in order to study its potential application for treatment of neurodegenerative diseases. BMSC were harvested from male rats and cultured in DMEM supplemented with 20% fetal bovine serum. At passage 6 the total RNA was isolated using TriZol reactive. RT-PCRs to evaluate the expression of NGF and GDNF using specific primers were carried out. Our results indicate that rat BMSC have potential to produce NGF and GDNF. We have not found any report in favor of GDNF or NGF production from rat BMSC.     

Bacterial luciferase is naturally destabilized in Mycobacterium tuberculosis and can be used to monitor changes in gene expression

Reporter systems efficient at monitoring temporal gene expression in slow-growing mycobacteria would significantly aid the characterization of gene expression in specific environments. Bacterial luciferase is a reporter that has not been widely used to study gene expression in mycobacteria. This report describes the determination of the degradation of bacterial luciferase in Mycobacterium tuberculosis H37Ra and its utility as a reporter of temporal gene expression in this slow-growing mycobacterium. The inducible/repressible alanine dehydrogenase promoter of M. tuberculosis H37Rv was used to track the decay kinetics of Vibrio harveyi luciferase in both mid-log phase and stationary phase grown M. tuberculosis H37Ra, which proved to be highly similar during both phases of growth. The luciferase reporter was then used to detect changes in expression from the heat-shock promoter, phsp60, of M. bovis BCG during M. tuberculosis H37Ra growth in culture. Quantitative real-time PCR analysis of groEL2, the hsp60 homologue in M. tuberculosis, displayed a similar pattern of expression to phsp60-driven luciferase. These results strongly suggest that the luciferase reporter can be used to monitor temporal changes in gene expression in M. tuberculosis and may serve as a novel system to examine gene expression under specific conditions.