Pro-BDNF–induced synaptic depression and retraction at developing neuromuscular synapses

Postsynaptic cells generate positive and negative signals that retrogradely modulate presynaptic function. At developing neuromuscular synapses, prolonged stimulation of muscle cells induces sustained synaptic depression. We provide evidence that pro–brain-derived neurotrophic factor (BDNF) is a negative retrograde signal that can be converted into a positive signal by metalloproteases at the synaptic junctions. Application of pro-BDNF induces a dramatic decrease in synaptic efficacy followed by a retraction of presynaptic terminals, and these effects are mediated by presynaptic pan-neurotrophin receptor p75 (p75^NTR), the pro-BDNF receptor. A brief stimulation of myocytes expressing cleavable or uncleavable pro-BDNF elicits synaptic potentiation or depression, respectively. Extracellular application of metalloprotease inhibitors, which inhibits the cleavage of endogenous pro-BDNF, facilitates the muscle stimulation–induced synaptic depression. Inhibition of presynaptic p75^NTR or postsynaptic BDNF expression also blocks the activity-dependent synaptic depression and retraction. These results support a model in which postsynaptic secretion of a single molecule, pro-BDNF, may stabilize or eliminate presynaptic terminals depending on its proteolytic conversion at the synapses.     

Roosting patterns in a captive colony of short-nosed fruit bat Cynopterus sphinx (Vahl)

Development of roosting patterns under a limited resource was studied in the short-nosed fruit bat C. sphinx in captivity. Spatial fidelity during the resting period (day time) and the individual male bat's presence/absence in the roost (occupancy index) were estimated during the active period (night time). Results show the presence of three groups on the basis of spatial fidelity. The first group was associated with the tent consisting of a harem male and seven females. The second group stayed near to the harem. The third group consisting of two males showed little occupancy index and no spatial fidelity. Female turnover between the first and second groups, and harem male replacement were observed. These findings of male groupings and female loyalty on the basis of "resource", suggest that resource defence polygyny is the primary mating strategy in C. sphinx.     

Differential effects of transient and sustained activation of BDNF‐TrkB signaling

Brain‐derived neurotrophic factor (BDNF) serves a pleiotropic role in the central nervous system, ranging from promoting neuronal survival and differentiation during development and synaptic modulation in the adult. An important, yet unanswered question is how BDNF could serve such diverse functions, sometimes in the same cell. At least two modes of BDNF actions have been elucidated so far based on BDNF signaling kinetics and/or the activity status of the responding neurons. Acute and gradual increases in extracellular BDNF concentrations elicit, respectively, transient and sustained activation of TrkB receptor and its downstream signaling, leading to differential molecular and cellular functions. In cultured neurons, sustained TrkB activation promotes neuronal dendritic arborization and spinogenesis, whereas transient TrkB activation facilitates dendritic growth and spine morphogenesis. In hippocampal slices, slow delivery of BDNF facilitates LTP, whereas fast application of BDNF enhances basal synaptic transmission in schaffer collateral synapses. High‐frequency stimulation of neurons converts BDNF‐induced TrkB signaling from a transient to a sustained mode. These initial insights lay the foundation for future investigation of the BDNF‐TrkB pathway, and analogous signaling pathways to gain a comprehensive understanding to enable translational research. © 2018 Wiley Periodicals, Inc. Develop Neurobiol 78: 647–659, 2018     

Transition of nonharem male to harem male status in the short-nosed fruit bat Cynopterus sphinx

The short-nosed fruit bat Cynopterus sphinx is known to exhibit resource defence polygyny as its primary mating strategy. Tent construction by harem males to recruit females represents a heavy investment of time and effort, which is not done by nonharem males. The previously unobserved mode of harem formation by the solitary males was studied using mark-recapture and radio-telemetry. In our observation, the solitary males roosting near to harems started recruiting females by occupying the tent abandoned by the harems. This result suggests that the transition of nonharem male to harem male status possibly by a previously unobserved mode and the female recruitment is associated with resource (roost). It implies that the solitary males are actively involving in female recruitment and also presumably mating.     

Utilization of cyanide as nitrogenous substrate by Pseudomonas fluorescens NCIMB 11764: evidence for multiple pathways of metabolic conversion.

The growth of Pseudomonas fluorescens NCIMB 11764 on cyanide as the sole nitrogen source was accomplished by use of a modified fed-batch cultivation procedure. Previous studies showing that cyanide metabolism in this organism is both an oxygen-dependent and an inducible process, with CO2 and ammonia representing conversion products, were confirmed. However, washed cells (40 mg ml-1 [dry weight]) metabolized cyanide at concentrations far exceeding those previously described; 85% of 50 mM KCN was degraded in 6 h. In addition, two other C1 metabolites were detected in incubation mixtures; their identities were confirmed as formamide and formate by 13C nuclear magnetic resonance spectrocopy, high-pressure liquid chromatography, radioisotopic trapping experiments, and other analytical means. The relative yields of all four metabolites (CO2, formamide, formate, and ammonia) were shown to be dependent on the KCN concentration and availability of oxygen; at 0.5 to 10 mM substrate, CO2 was the major C1 product, whereas at 20 and 50 mM substrate, formamide and formate were principally formed. The latter two metabolites also accumulated during prolonged anaerobic incubation, suggesting that P. fluorescens NCIMB 11764 can elaborate several pathways of cyanide conversion. One is formally similar to that proposed previously (R. E. Harris and C. J. Knowles, FEMS Microbiol. Lett. 20:337-341, 1983), involving the oxygen-dependent conversion of cyanide to CO2 and ammonia. The other two, occurring in the presence or absence of oxygen, involve separate reactions to yield, respectively, formate plus ammonia or formamide.(ABSTRACT TRUNCATED AT 250 WORDS)     

Osteopontin improves in vitro development of porcine embryos and decreases apoptosis

An optimal environment for fertilization and early embryonic development is provided by the mammalian oviduct and uterus. The secretory cells lining the lumen of the oviduct and uterus synthesize and secrete proteins that have been shown to interact with and influence the activities of gametes and embryos. Western blotting in this study demonstrated that a 50-kDa secreted phosphoprotein 1 (SPP1) form was present in the uterus on Days 0, 3, and 5 in pregnant and nonbred gilts, and the concentration of SPP1 on Day 0 was higher than on Days 3 and 5 in pregnant gilts, but in nonbred gilts the concentration of SPP1 on Day 0 was higher than Day 3, but not Day 5. In addition, we show that addition of 0.1 microg/ml SPP1 to the culture medium after fertilization increased the percent cleaved (24 hr: 23.6 +/- 1.29(a) vs. 18.7 +/- 0.65(b) (2-cell %)), and the percent blastocyst (37.2 +/- 1.12(a) vs. 30.9 +/- 0.56(b)) derived from IVF (P < 0.05). In parthenogenetic-derived embryos the percent cleaved was increased due to SPP1 at 24 hr (24.0 +/- 1.59(a) vs. 19.7 +/- 1.59(b) (>2-cell %)), and at 48 hr (72.9+/- 2.99(a) vs. 63.3 +/- 2.99(b)), but not the percent blastocyst. By TUNEL assay, SPP1 decreased both apoptosis (7.9 +/- 0.04(a) vs. 13.1 +/- 0.02(b)) and the percent fragmentation (45.2 +/- 0.07(a) vs. 58.8 +/- 0.03(b)). We conclude that SPP1 can improve development in vitro possibly by reducing the rate of apoptosis.     

The establishment of an ELISA for the detection of pregnancy-associated glycoproteins (PAGs) in the serum of pregnant cows and heifers

The pregnancy-associated glycoproteins (PAGs) are a large gene family expressed in trophoblast cells of ruminant ungulates. The detection of PAGs (more specifically, PAG-1) in maternal serum has served as the basis for pregnancy detection in cattle. Unfortunately, PAG-1 and/or antigenically-related PAGs exhibit a long half-life in maternal serum (>8 d) and can be detected 80-100 d post-partum, thereby producing false positives in animals bred within 60-d of calving. The goal of the present studies was to develop a monoclonal-based assay that targeted early-pregnancy PAGs whose persistence in maternal serum post-partum might be relatively short-lived. Three anti-PAG monoclonal antibodies that recognized distinct subsets of PAGs were selected and used as trapping reagents in a 'sandwich' type of enzyme-linked immunosorbant assay (ELISA). A polyclonal antiserum with broad specificity was used for detecting bound PAGs. A total of 42 cows and heifers were bled daily on day 15, days 22 to 28, and then weekly throughout pregnancy and for 10 weeks (approximately 70 d) into the post-partum period. The ELISA was able to detect PAG in maternal serum of all animals unambiguously by day 28 post-insemination (PAG concentration: 8.75 +/- 3.04 ng/mL). In maternal serum, PAG concentrations peaked during the week of parturition at 588.9 +/- 249.9 ng/mL, and after calving, PAG was completely cleared (half-life: 4.3 d) by eight-week post-partum in 38 of 40 of the animals tested and was at very low concentrations in the remaining two (1.4 and 4.9 ng/mL, respectively). In summary, a monoclonal-based assay has been established that is sensitive enough to detect PAG in maternal serum by the forth week of pregnancy, but does not suffer from carry-over of antigen from a previous pregnancy.