Population trends for humpback whales (Megaptera novaeangliae) foraging in the Francisco Coloane Coastal‐Marine Protected Area,Magellan Strait,Chile

In 2003 a feeding aggregation of southeastern Pacific humpback whales (Megaptera novaeangliae) was reported in the Magellan Strait. While Chile established its first marine national park in the Strait to protect humpback whale habitat, fatal ship strikes remain a concern because of overlap with a busy shipping lane. To better understand population risk, we estimated abundance and survival for this population using Bayesian robust‐design mark‐recapture models fit to photographic data from 2004 to 2016. Overall, the model estimated a total of 204 whales (95% CI: 199–210) during the last 12 yr, and 93 (95% CI: 86–100) in the 2016/2017 austral summer. The population grew at 2.3% (CI: 2.1%–3.1%), an annual increase of two whales. Annual survival (including calves) was estimated at 0.892 (CI: 0.871–0.910). Our results corroborate a persistent feeding population, but one that is increasing relatively slowly. Owing to its vulnerability stemming from its small size, coupled with significant overlap with a busy shipping lane, we argue this subpopulation is at significant risk from ship strikes and may be one of the few populations where anthropogenic mortalities could regulate population dynamics. We therefore encourage continued monitoring via photographic mark‐resighting surveys, and analyses explicitly investigating potential population‐level ship strike effects.     

Ultrastructure and motility of the caudal epididymis spermatozoa from the volcano mouse (Neotomodon alstoni alstoni Merriam, 1898)

The volcano mouse Neotomodon alstoni alstoni is a genus endemic to the higher elevations of the Mexican transvolcanic belt. In the present study we examined for the first time the morphological features of the spermatozoa taken from the caudal epididymis of this species by transmission and scanning electron microscopy. Spermatozoan motility was studied in sucrose and bicarbonate solutions; vitality and morphology were observed by light microscopy. Transmission electron microscopy shows that the head of spermatozoon is asymmetric and possesses a large and curved hook. The axoneme of the spermatozoan tail is highly developed at fibers 1, 5, and 6. Absolute and relative measurements of the length of the head, the midpiece, and the rest of the tail were also obtained. N. alstoni alstoni spermatozoa were hyperactive in the presence of 290 mM sucrose and 10 and 20 nM bicarbonate solutions exhibited high motility (180-190 microm/sec), and high flagellum beating frequency (10-12 Hz). In contrast, the spermatozoa in 310 mM sucrose solution showed scarce motility (13.5 +/- 3.8 microm/sec) and low beating frequency (1.5 +/- 0.4 Hz). It is proposed that the volcano mouse spermatozoa possess some features very similar to other mammalian spermatozoa and that bicarbonate triggers caudal epididymal sperm motility of this species. J. Exp. Zool. 287:316-326, 2000.     

Hydrophobic interaction between contiguous residues in the S6 transmembrane segment acts as a stimuli integration node in the BK channel

Large-conductance Ca²⁺- and voltage-activated K⁺ channel (BK) open probability is enhanced by depolarization, increasing Ca²⁺ concentration, or both. These stimuli activate modular voltage and Ca²⁺ sensors that are allosterically coupled to channel gating. Here, we report a point mutation of a phenylalanine (F380A) in the S6 transmembrane helix that, in the absence of internal Ca²⁺, profoundly hinders channel opening while showing only minor effects on the voltage sensor active–resting equilibrium. Interpretation of these results using an allosteric model suggests that the F380A mutation greatly increases the free energy difference between open and closed states and uncouples Ca²⁺ binding from voltage sensor activation and voltage sensor activation from channel opening. However, the presence of a bulky and more hydrophobic amino acid in the F380 position (F380W) increases the intrinsic open–closed equilibrium, weakening the coupling between both sensors with the pore domain. Based on these functional experiments and molecular dynamics simulations, we propose that F380 interacts with another S6 hydrophobic residue (L377) in contiguous subunits. This pair forms a hydrophobic ring important in determining the open–closed equilibrium and, like an integration node, participates in the communication between sensors and between the sensors and pore. Moreover, because of its effects on open probabilities, the F380A mutant can be used for detailed voltage sensor experiments in the presence of permeant cations.     

Molecular Requirements for Ethanol Differential Allosteric Modulation of Glycine Receptors Based on Selective Gβγ Modulation

It is now believed that the allosteric modulation produced by ethanol in glycine receptors (GlyRs) depends on alcohol binding to discrete sites within the protein structure. Thus, the differential ethanol sensitivity of diverse GlyR isoforms and mutants was explained by the presence of specific residues in putative alcohol pockets. Here, we demonstrate that ethanol sensitivity in two ligand-gated ion receptor members, the GlyR adult α₁ and embryonic α₂ subunits, can be modified through selective mutations that rescued or impaired Gβγ modulation. Even though both isoforms were able to physically interact with Gβγ, only the α₁ GlyR was functionally modulated by Gβγ and pharmacological ethanol concentrations. Remarkably, the simultaneous switching of two transmembrane and a single extracellular residue in α₂ GlyRs was enough to generate GlyRs modulated by Gβγ and low ethanol concentrations. Interestingly, although we found that these TM residues were different to those in the alcohol binding site, the extracellular residue was recently implicated in conformational changes important to generate a pre-open-activated state that precedes ion channel gating. Thus, these results support the idea that the differential ethanol sensitivity of these two GlyR isoforms rests on conformational changes in transmembrane and extracellular residues within the ion channel structure rather than in differences in alcohol binding pockets. Our results describe the molecular basis for the differential ethanol sensitivity of two ligand-gated ion receptor members based on selective Gβγ modulation and provide a new mechanistic framework for allosteric modulations of abuse drugs.     

��-Amyloid Causes Depletion of Synaptic Vesicles Leading to Neurotransmission Failure

Alzheimer disease is a progressive neurodegenerative brain disorder that leads to major debilitating cognitive deficits. It is believed that the alterations capable of causing brain circuitry dysfunctions have a slow onset and that the full blown disease may take several years to develop. Therefore, it is important to understand the early, asymptomatic, and possible reversible states of the disease with the aim of proposing preventive and disease-modifying therapeutic strategies. It is largely unknown how amyloid β-peptide (Aβ), a principal agent in Alzheimer disease, affects synapses in brain neurons. In this study, we found that similar to other pore-forming neurotoxins, Aβ induced a rapid increase in intracellular calcium and miniature currents, indicating an enhancement in vesicular transmitter release. Significantly, blockade of these effects by low extracellular calcium and a peptide known to act as an inhibitor of the Aβ-induced pore prevented the delayed failure, indicating that Aβ blocks neurotransmission by causing vesicular depletion. This new mechanism for Aβ synaptic toxicity should provide an alternative pathway to search for small molecules that can antagonize these effects of Aβ.     

Canonical Wnt3a Modulates Intracellular Calcium and Enhances Excitatory Neurotransmission in Hippocampal Neurons

A role for Wnt signal transduction in the development and maintenance of brain structures is widely acknowledged. Recent studies have suggested that Wnt signaling may be essential for synaptic plasticity and neurotransmission. However, the direct effect of a Wnt protein on synaptic transmission had not been demonstrated. Here we show that nanomolar concentrations of purified Wnt3a protein rapidly increase the frequency of miniature excitatory synaptic currents in embryonic rat hippocampal neurons through a mechanism involving a fast influx of calcium from the extracellular space, induction of post-translational modifications on the machinery involved in vesicle exocytosis in the presynaptic terminal leading to spontaneous Ca²⁺ transients. Our results identify the Wnt3a protein and a member of its complex receptor at the membrane, the low density lipoprotein receptor-related protein 6 (LRP6) coreceptor, as key molecules in neurotransmission modulation and suggest cross-talk between canonical and Wnt/Ca²⁺ signaling in central neurons.     

Intrathecal administration of autologous mesenchymal stromal cells for spinal cord injury: Safety and efficacy of the 100/3 guideline

Background aims

Cell therapy with autologous mesenchymal stromal cells (MSCs) in patients with spinal cord injury (SCI) is beginning, and the search for its better clinical application is an urgent need.

Adenosine A<Subscript>2A</Subscript> receptor regulates expression of vascular endothelial growth factor in feto-placental endothelium from normal and late-onset pre-eclamptic pregnancies

We aim to investigate whether A_2A/nitric oxide-mediated regulation of vascular endothelial growth factor (VEGF) expression is impaired in feto-placental endothelial cells from late-onset pre-eclampsia. Cultures of human umbilical vein endothelial cells (HUVECs) and human placental microvascular endothelial cells (hPMECs) from normal and pre-eclamptic pregnancies were used. Assays by using small interference RNA (siRNA) for A_2A were performed, and transfected cells were used for estimation of messenger RNA (mRNA) levels of VEGF, as well as for cell proliferation and angiogenesis in vitro. CGS-21680 (A_2A agonist, 24 h) increases HUVEC and hPMEC proliferation in a dose response manner. Furthermore, similar to CGS-21680, the nitric oxide donor, S-nitroso-N-acetyl-penicillamine oxide (SNAP), increased cell proliferation in a dose response manner (logEC₅₀ 10^?9.2 M). In hPMEC, CGS-21680 increased VEGF protein levels in both normal (～1.5-fold) and pre-eclamptic pregnancies (～1.2-fold), an effect blocked by the A_2A antagonist, ZM-241385 (10^?5 M) and the inhibitor of NO synthase, N _ω-nitro-L-arginine methyl ester hydrochloride (L-NAME). Subsequently, SNAP partially recovered cell proliferation and in vitro angiogenesis capacity of cells from normal pregnancies exposed to siRNA for A_2A. CGS-21680 also increased (～1.5-fold) the level of VEGF mRNA in HUVEC from normal pregnancies, but not in pre-eclampsia. Additionally, transfection with siRNA for A_2A decrease (～30 %) the level of mRNA for VEGF in normal pregnancy compared to untransfected cells, an effect partially reversed by co-incubation with SNAP. The A_2A-NO-VEGF pathway is present in endothelium from microcirculation and macrocirculation in both normal and pre-eclamptic pregnancies. However, NO signaling pathway seems to be impaired in HUVEC from pre-eclampsia.