Diet of the Indochinese silvered langur (Trachypithecus germaini) in Kien Luong Karst area,Kien Giang Province

The Indochinese silvered langur (Trachypithecus germaini) is distributed to the west of Mekong River in Cambodia, Lao PDR, Thailand and Vietnam. During a two‐year study, from May 2014 to May 2016, we collected 320.44 hr of behavior, with 17,040 feeding bouts recorded (142 hr) for T. germaini on Chua Hang Karst Mountain, Kien Luong District, Kien Giang Province, Vietnam. Feeding accounted for 45% of the Indochinese silvered langurs’ activity budget. The plant diet of the Indochinese silvered langurs was principally composed of young leaves (58%), followed by mature leaves (9.5%), fruits (22.7%), flowers (4.7%), buds (3.3%), petioles (1.2%), and other (0.5%). A total of 58 plant species were fed on by the silvered langurs, and leaves of eight species (Phyllathus reticulatus, Ficus rumphii, Ficus tinctoria, Ficus microcarpa, Cayratia trifolia, Streblus ilicifolia, Combretum latifolium, and Streblus asper) were fed on throughout the year. P. reticulatus was most frequently eaten (13.9% feeding time, n = 1,733). Food selection differed significantly between months and seasons. The Indochinese silvered langurs ate 27 plant species in the wet season compared with 23 plant species in the dry season. Leaf chemical composition of two food categories, 16 eaten species (with 10 most frequently consumed species and six least consumed species), and four noneaten species, were analyzed. Feeding samples from eaten species in the Indochinese silvered langurs's diet contained lower amounts of condensed tannin, lignin, protein, ash, and lipids, but a higher amount of total sugar compared with samples from noneaten species. Furthermore, the most frequently consumed species contained lower amounts of lignin compared with the less frequently consumed species. Using a generalized linear model with five variables, including neutral detergent fiber (NDF), total sugar, lignin, lipid, and calcium (Ca) indicated that NDF positively correlated and lignin content negatively correlated with feeding records in the diet of these langur.     

Quantitative Modeling of GRK-Mediated β2AR Regulation

We developed a unified model of the GRK-mediated β2 adrenergic receptor (β2AR) regulation that simultaneously accounts for six different biochemical measurements of the system obtained over a wide range of agonist concentrations. Using a single deterministic model we accounted for (1) GRK phosphorylation in response to various full and partial agonists; (2) dephosphorylation of the GRK site on the β2AR; (3) β2AR internalization; (4) recycling of the β2AR post isoproterenol treatment; (5) β2AR desensitization; and (6) β2AR resensitization. Simulations of our model show that plasma membrane dephosphorylation and recycling of the phosphorylated receptor are necessary to adequately account for the measured dephosphorylation kinetics. We further used the model to predict the consequences of (1) modifying rates such as GRK phosphorylation of the receptor, arrestin binding and dissociation from the receptor, and receptor dephosphorylation that should reflect effects of knockdowns and overexpressions of these components; and (2) varying concentration and frequency of agonist stimulation “seen” by the β2AR to better mimic hormonal, neurophysiological and pharmacological stimulations of the β2AR. Exploring the consequences of rapid pulsatile agonist stimulation, we found that although resensitization was rapid, the β2AR system retained the memory of the previous stimuli and desensitized faster and much more strongly in response to subsequent stimuli. The latent memory that we predict is due to slower membrane dephosphorylation, which allows for progressive accumulation of phosphorylated receptor on the surface. This primes the receptor for faster arrestin binding on subsequent agonist activation leading to a greater extent of desensitization. In summary, the model is unique in accounting for the behavior of the β2AR system across multiple types of biochemical measurements using a single set of experimentally constrained parameters. It also provides insight into how the signaling machinery can retain memory of prior stimulation long after near complete resensitization has been achieved.     

La crise du transformisme

Ohne Zusammenfassung     

The strength of SMAD1/5 activity determines the mode of stem cell division in the developing spinal cord

The different modes of stem cell division are tightly regulated to balance growth and differentiation during organ development and homeostasis. However, the mechanisms controlling such events are not fully understood. We have developed markers that provide the single cell resolution necessary to identify the three modes of division occurring in a developing nervous system: self-expanding, self-renewing, and self-consuming. Characterizing these three modes of division during interneuron generation in the developing chick spinal cord, we demonstrated that they correlate to different levels of activity of the canonical bone morphogenetic protein effectors SMAD1/5. Functional in vivo experiments showed that the premature neuronal differentiation and changes in cell cycle parameters caused by SMAD1/5 inhibition were preceded by a reduction of self-expanding divisions in favor of self-consuming divisions. Conversely, SMAD1/5 gain of function promoted self-expanding divisions. Together, these results lead us to propose that the strength of SMAD1/5 activity dictates the mode of stem cell division during spinal interneuron generation.     

Orthologs of key vertebrate neural genes are expressed during neurogenesis in the annelid Platynereis dumerilii

SUMMARY The molecular mechanisms underlying the formation and patterning of the nervous system are relatively poorly understood for lophotrochozoans (like annelids) as compared with ecdysozoans (especially Drosophila ) and deuterostomes (especially vertebrates). Therefore, we have undertaken a candidate gene approach to study aspects of neurogenesis in a polychaete annelid Platynereis dumerilii . We determined the spatiotemporal expression for Platynereis orthologs of four genes ( SoxB, Churchill, prospero / Prox , and SoxC) known to play key roles in vertebrate neurogenesis. During Platynereis development, SoxB is expressed in the neuroectoderm and its expression switches off when committed neural precursors are formed. Subsequently, Prox is expressed in all differentiating neural precursors in the central and peripheral nervous systems. Finally, SoxC and Churchill are transcribed in patterns consistent with their involvement in neural differentiation. The expression patterns of Platynereis SoxB and Prox closely resemble those in Drosophila and vertebrates—this suggests that orthologs of these genes play similar neurogenic roles in all bilaterians. Whereas Platynereis SoxC , like its vertebrate orthologs, plays a role in neural cell differentiation, related genes in Drosophila do not appear to be involved in neurogenesis. Finally, conversely to Churchill in Platynereis , vertebrate orthologs of this gene are expressed during neuroectoderm formation, but not later during nerve cell differentiation; in the insect lineage, homologs of these genes have been secondarily lost. In spite of such instances of functional divergence or loss, the present study shows conspicuous similarities in the genetic control of neurogenesis among bilaterians. These commonalities suggest that key features of the genetic program for neurogenesis are ancestral to bilaterians.     

Atx1-like chaperones and their cognate P-type ATPases: copper-binding and transfer

Copper is an essential yet toxic metal ion. To satisfy cellular requirements, while, at the same time, minimizing toxicity, complex systems of copper trafficking have evolved in all cell types. The best conserved and most widely distributed of these involve Atx1-like chaperones and P_1B-type ATPase transporters. Here, we discuss current understanding of how these chaperones bind Cu(I) and transfer it to the Atx1-like N-terminal domains of their cognate transporter.     

Polypyrimidine Tract Binding Protein Prevents Activity of an Intronic Regulatory Element That Promotes Usage of a Composite 3��-Terminal Exon

Alternative splicing of 3′-terminal exons plays a critical role in gene expression by producing mRNA with distinct 3′-untranslated regions that regulate their fate and their expression. The Xenopus α-tropomyosin pre-mRNA possesses a composite internal/3′-terminal exon (exon 9A9′) that is differentially processed depending on the embryonic tissue. Exon 9A9′ is repressed in non-muscle tissue by the polypyrimidine tract binding protein, whereas it is selected as a 3′-terminal or internal exon in myotomal cells and adult striated muscles, respectively. We report here the identification of an intronic regulatory element, designated the upstream terminal exon enhancer (UTE), that is required for the specific usage of exon 9A9′ as a 3′-terminal exon in the myotome. We demonstrate that polypyrimidine tract binding protein prevents the activity of UTE in non-muscle cells, whereas a subclass of serine/arginine rich (SR) proteins promotes the selection of exon 9A9′ in a UTE-dependent way. Morpholino-targeted blocking of UTE in the embryo strongly reduced the inclusion of exon 9A9′ as a 3′-terminal exon in the endogenous mRNA, demonstrating the function of UTE under physiological circumstances. This strategy allowed us to reveal a splicing pathway that generates a mRNA with no in frame stop codon and whose steady-state level is translation-dependent. This result suggests that a non-stop decay mechanism participates in the strict control of the 3′-end processing of the α-tropomyosin pre-mRNA.