96 Matching Annotations
  1. Apr 2019
    1. In our monosynaptic retrograde tracing with Cre-dependent rabies virus, although less robust than the projection from the ZI, we found a substantial projection to PVT glutamate neurons from the parasubthalamic nucleus (PSTh) (Fig. 4I and fig. S11) (27, 28).

      Analysis of the inputs to PVH VGlut2 neurons showed that these neurons receive input from the parasubthalamic nucleus, a brain region with previously described roles in appetite.

    2. In spite of the light aversion, photostimulation of VGATZI-PVTterminals significantly increased the time mice spent on the illuminated side to 61% when high-fat food was available (Fig. 3D). Photostimulation increased high-fat food intake in bright light (Fig. 3E).

      Mice that received stimulation of ZI GABA terminals in the PVT activated spent more time in the light compartment in the presence of high-fat food even though mice usually avoid places that are brightly lit. This means that the stimulation of the ZI to PVT projection was able to overcome the aversive nature of the light.

    3. o test the time course and efficiency of optogenetic activation of VGATZI-PVT inhibitory inputs to evoke feeding, we used a laser stimulation protocol of 10 s ON (20 Hz) followed by 30 s OFF for more than 20 min to study ZI axon stimulation in PVT brain slices and feeding behavior. Stimulation of ZI axons with this protocol hyperpolarized and inhibited PVT glutamatergic neurons each time the light was activated (Fig. 3A). Mice immediately started feeding for each of the 30 successive trials of ZI axon laser stimulation (Fig. 3B and movie S4). The mean latency to initiate feeding was 2.4 ± 0.6 s when we used laser stimulation of 20 Hz (Fig. 3C). This is almost 100 times faster than that reported for optogenetic stimulation of the AgRP neuron soma and 500 times faster than stimulation of AgRP-PVT axon terminals (19, 20). As soon as the laser was turned off, the mice stopped eating.

      The authors wanted to compare the latency of eating onset upon stimulation of ZI projections to the PVT to that of AgRP neurons which are known to promote food intake in response to hunger. They found that mice start to eat much faster than mice did in previous reports where AgRP neurons were stimulated or when AgRP projections to the PVT were stimulated.

      They did this by intermittently turning on the stimulation light for 10 seconds followed by 30 seconds of no stimulation. With each 10 second of light on, they measured how long it took for the mice to begin eating.

    4. photostimulation of ZI VGAT-ChIEF-tdTomato terminals in the PVT evoked GABA-mediated inhibitory currents in PVT vGlut2-GFP neurons (Fig. 2D).

      Stimulation of ZI GABA neuron projections (terminals) in the PVT with blue light led to inhibition of PVT excitatory neurons. This finding confirms the rabies tracing result and shows that the connection between ZI neurons and PVT neurons is inhibitory.

    5. Food deprivation lasting 24 hours increased ZI GABA neuron activity and excitatory neurotransmission to these neurons

      Recordings made in brain slices show that ZI GABA neurons fire more ie. are more active in food deprived mice. Further, inputs from other neurons that excite/activate ZI GABA neurons are increased.

      See this video that explains how information is transmitted between neurons: Molecular mechanism of synapse function

      Therefore, increased ZI GABA neuron activity correlates with hunger.

    6. Ghrelin, a hormone that signals a reduced gut energy state (12), excited ZI GABA neurons and increased excitatory synaptic input onto these neurons (Fig. 1, K to M, and fig. S2).

      Ghrelin is produced in the stomach. Its synthesis is increased by food deprivation.

      Application of Ghrelin to the brain slices containing ZI GABA neurons increases their activity similar to food deprivation.

  2. Mar 2019
    1. Stimulation of PSTh glutamatergic neuron terminals in the PVT inhibited food intake (Fig. 4L).

      PVT VGlut2 neurons decrease food intake. Therefore stimulation of excitatory neurons upstream of them ie. the vGlut2 PSTh neurons was also found to increase food intake.

    2. Brain slice electrophysiology confirmed that optogenetic activation of PSTh glutamatergic neuron terminals in the PVT evoked strong glutamate-mediated postsynaptic excitatory currents in PVT vGlut2-GFP neurons, suggesting a functional role for PSTh glutamate neurons in the synaptic excitation of PVT glutamate neurons (Fig. 4K).

      The authors confirmed that stimulation of the PSTh terminals in the PVT was able to activate PVT neurons. ie. induce excitatory activity in the PVT cells.

      This confirms the rabies tracing result and shows that the connection between the PSTh and the PVT is functional.

    3. Ablation of PVT vGluT2 neurons substantially increased both food intake and body weight gain for an extended period (16-week study) (fig. S10, G and H).

      The increase in food intake and body weight gain with PVT neuron ablation shows that these cells are important for body weight maintenance.

      This finding is opposite to what was found when ZI GABA neurons were ablated, suggesting that PVT neurons are downsteam of ZI GABA neurons and have an opposing effect on food intake and body weight.

    4. Ablation of ZI GABA neurons decreased long-term food intake and reduced body weight gain by 53% over 8 weeks (Fig. 3, J and K).

      When the ZI GABA neurons were killed, the mice could no long maintain their normal body weight and ate less food than control mice that had their ZI GABA neurons intact. This suggests that these cells are required for normal food intake and body weight maintenance.

    5. After the days of photostimulation were completed, mice showed a significantly reduced food intake compared with that of controls (Fig. 3H).

      The authors measured daily food intake for 15 days during the stimulation protocol. They then continued measuring daily food intake in the absence of stimulation.

      The mice likely reduced their food consumption when the stimulation protocol ceased due to satiety signals that normally prevent overeating in the absence of the manipulation of the ZI to PVT pathway.

    6. To test the hypothesis that the VGATZI-PVT pathway is involved in a reward state, we explored the motivational valence of VGATZI-PVT in mice by using a two-chamber place preference test. In the absence of available food, optogenetic activation of the VGATZI-PVT pathway evoked a significant preference for the chamber associated with laser stimulation compared with the control chamber (Fig. 3, F and G).

      Motivational valence is the degree to which something is perceived as pleasurable (positive valence) or aversive (negative valence). The authors hypothesised that because the ZI to PVT projection promotes intake of foods that are pleasurable to eat and also makes mice overcome their aversion to light in order to eat that food, that stimulation of this pathway is pleasurable or rewarding for the mice.

      They tested this by placing the animals in a box with two identical compartments. The mice were able to freely move around the box. On one side of the chamber the mice received stimulation of their ZI-PVT neurons while the stimulation was turned off when the mice were on the other side.

      That the mice preferred to spend more time in the compartment where they received stimulation of the ZI-PVT pathway suggest that stimulation of the neurons is pleasurable for the animal.

    7. To further confirm the importance of the VGATZI-PVT projection in mediating ZI GABA neuron control of food intake, the type A GABA (GABAA) receptor antagonist bicuculline (Bic) was microinjected into the PVT 10 min before photostimulation of VGATZI-PVT axon terminals. Bic attenuated photostimulation-evoked feeding (Fig. 2K). That Bic did not completely block photostimulation-evoked food intake could be a diffusion limitation of Bic after application, or ZI VGAT-Cre neurons may coexpress other neurotransmitters responsible for the remaining action

      The authors found that blocking the function of the GABA receptor (GABA-A receptor) in the PVT could blunt the increase in food intake mediated by stimulation of ZI terminals in the PVT. This suggests that GABA is an important neurotransmitter underlying this effect.

      The limitations of this approach include that the authors cannot control the spread of the GABA-A receptor blocker or that other neurotransmitters might be involved.

    8. ZI GABA neurons project to multiple brain regions, including the hypothalamus and midline thalamus (fig. S6). We therefore measured the relative contribution of stimulation of ZI somata with selective stimulation of ZI axons targeting the PVT. Stimulation of ZI VGAT cell bodies or VGATZI-PVT terminals in the PVT evoked similar levels of feeding (Fig. 2J).

      This suggests that even though ZI GABA neurons project to other brain regions in addition to the PVT, the PVT projection appears to be the most important mediator of increased food intake. This is because ZI GABA cell body stimulation and stimulation of the projections to the PVT evoked similar degrees of food intake.

    9. Although mice prefer sweet and high-fat foods when stimulation is off,

      Mice will avidly consume high-fat and sweet foods even when not hungry. This is because these foods are palatable, meaning that they are pleasurable or rewarding to eat and so will be consumed even when nutrition requibments are met.

    10. Photostimulation of ZI-PVT inhibitory axons evoked gnawing, but not eating, of nonnutritional wood sticks (fig. S5, A and B); photostimulation leading to food intake eliminated subsequent evoked stick gnawing. A priori wood gnawing had no effect on photostimulation-evoked food intake (fig. S5, C and D).

      The authors conclude that the food intake seen with ZI stimulation is not because the manipulation increases gnawing behavior directed at any object, but directs behavior towards edible sources of food.

    11. In control mice with tdTomato expression, consumption was only 4% of their 24-hour intake during the same period (Fig. 1E).

      Lack of food intake in a control animal that was injected with an AAV expressing only a fluorescent protein shows that the result seen in ChIEF expressing mice was not due to non-specific effects of AAV injection or protein expression in the neurons.

    12. Satiety feedback signals can thus attenuate ZI-induced feeding.

      Signals from the body inform the brain that sufficient food has been eaten (satiety). These include release of hormones from the gut as well as stomach distention.

      The finding that ZI-stimulated mice will not eat indefinitely suggests that satiety feedback mechanisms are still intact.

    13. Food deprivation lasting 24 hours increased inhibitory synaptic neurotransmission to PVT glutamate neurons (fig. S4)

      In food deprived mice, PVT glutamate neurons receive more inhibitory inputs compared to fed mice. These may come from ZI inhibitory GABA neurons which the authors showed have increased activity upon food deprivation.

    14. confirmed that PVT glutamate neurons receive strong and direct innervation from ZI neurons (Fig. 2, B and C, and fig. S3).

      The authors confirm their anterograde tracing findings using retrograde tracing to show that ZI GABA neurons send projections to excitatory neurons in the PVT.

    15. VGAT-Cre mice with ChIEF expression, bilateral laser stimulation (20 Hz) in the ZI increased food intake

      When ZI GABA neurons are activated by delivering blue light into the brains of the mice, the mice eat a large amount of food.

    16. ChIEF-tdTomato was selectively expressed in ZI GABA neurons

      The optogenetic tool ChIEF-tdTomato was found to be expressed only the ZI GABA neurons.

  3. Dec 2018
    1. larger fish have greater thermal inertia and increased cardiac capacity

      Thermal inertia is the ability of a body or object to maintain its temperature when ambient temperature changes. Larger objects have higher thermal inertia, so larger fish lose heat more slowly than smaller fish. Larger fish also have larger hearts, which can pump more blood.

    2. The largest size-based differences in energy intake were also observed in October (Fig. 6 and table S3), indicating that thermal niche expansion in this endothermic species results in high energetic reward.

      The increased temperature range allowed the tuna to forage and obtain energy more efficiently.

    3. Lower energy intake was observed during late summer (August and September), when bluefin tuna are moving up through the Southern California Bight (28° to 32°N).

      Lower energy intake during migrations.

  4. Jun 2018
    1. Many practicing ecologists still view large animals in general, and apex consumers in particular, as ecological passengers riding atop the trophic pyramid but having little impact on the structure below.

      There has previously been lack of appreciation for the role that top-down forces can have within a system, often until those organisms are removed.

      The authors are calling for a change in the lens through which ecosystem ecologists view the role of these species. Specifically, that the working hypothesis oof ecosystem ecologists should be that apex consumers play a fundamental role in any particular ecosystem's structure and stability until empirical research indicates otherwise.

    2. Bottom-up forces are ubiquitous and fundamental, and they are necessary to account for the responses of ecosystems to perturbations, but they are not sufficient. Top-down forcing must be included in conceptual overviews if there is to be any real hope of understanding and managing the workings of nature

      Given the numerous instances of trophic cascades noted in the literature, and the critical impacts that top-down forcing can have as noted above, it is necessary for researchers to consider both bottom-up and top-down controls when looking at ecosystem function, change, and decline.

    3. We propose that many of the ecological surprises that have confronted society over past centuries—pandemics, population collapses of species we value and eruptions of those we do not, major shifts in ecosystem states, and losses of diverse ecosystem services—were caused or facilitated by altered top-down forcing regimes associated with the loss of native apex consumers or the introduction of exotics.

      The disruption of many biological processes and natural ecosystem functions can be traced to the loss of predators shifting systems to a new state. Alternatively, introducing invasive exotic species that may outcompete native organisms, removing food sources of predators/herbivores, may cause ecosystem collapse via trophic cascade.

  5. Dec 2017
    1. Table 1

      mtDNA CO1 is a gene found within the mitochondria, it is used to measure the genetic difference between organisms. A higher mean indicates a larger difference between two organisms, which is indicative of being a different species. (JP)

    2. Fig. 2

      In general, this graph illustrates that as genetic distance between species increases (this is measured by Nei's D) then mtDNA divergence increases as well. Overall, compatibility between two different organisms will be less if they have high mtDNA divergence and a high Nei's D value. (JP)

    3. All the shrimps we studied are shallow water, fully marine forms with planktonic larvae.

      Main subjects studied. Planktonic larva is significant in this study because larva shrimp would migrate to different regions of the Isthmus of Panama which may be a significant contributor to speciation events ~J.D.A. (+ JP)

    4. Even the least divergent pairs show substantial reproductive isolation

      Species so closely related showed two differ clutches. Isolation could've been geographical, though nothing that could completely cut them off from each other since they are similar. If anything, this could infer that they could've been selective in mating, or aggressive in behavior to even mate, thus preventing creation of offspring between them. ~J.D.A

    5. The null hypothesis, that isolation was simultaneous but rates of divergence are highly variable, is incompatible with the observed pattern because metabolic enzymes, mtDNA, and mate recognition share no mechanistic basis that would cause their divergence rates to be automatically associated.

      Basically, the null is rejected because it contradicts the observed data. The null states that isolation occurred around at the same time, but the observed data shows divergence indicators such as metabolic enzymes, mtDNA, and mate recognition, all of which are not associated at a single mechanistic basis required for concurrent divergence. ~S.Z.

    6. However, they do show some distributional differences that could affect sensitivity to changing conditions associated with gradual rise of the isthmus.

      The physical location of the shrimp could effect the divergence associated with the gradual rise of isthmus. ~S.Z

    7. Pacific members of the most divergent pairs are found deeper in the intertidal or are rare in habitats with heavy sedimentation (25) (Fig. 2). Thus, larval avoidance (26) of shoaling waters over the rising isthmus (6, 7) may have accelerated genetic isolation of these pairs.

      The shrimp located closer to the sea floor had a slimmer chance of being pushed over the isthmus; therefore had a higher chance of isolation and divergence. ~S.Z.

    8. Our data can also be used to estimate rates of divergence in reproductive compatibility. Even the least divergent pairs show substantial reproductive isolation

      The less compatible they are the more they have diverged. ~S.Z.

    9. Geographic isolation is thought to permit divergence and speciation by disruption of gene flow

      The physical barrier created by the Isthmus of Panama prevented the exchange of genes; therefore, allowing the organism to develop differently on wither side of the barrier or diverge. (SZ)

    1. a phosphorylation-mimicking Thr205→Glu205 (T205E) tau variant coprecipitated significantly less with PSD-95 as compared with nonmutant and T205A (A, Ala) tau (Fig. 4C and fig. S21)

      Phosphorylation at T205 inhibits complex formation.

    2. T205 phosphorylation of tau is part of an Aβ toxicity–inhibiting response.

      Phosphorylation at T205 on tau limits Amyloid beta toxicity.

    3. p38γ regulated PSD-95/tau/Fyn complexes, likely at the level of PSD-95/tau interaction

      From Fig. 3 the authors conclude that p38y reduces PSD-95/tau/Fyn complex formation by affecting PSD-95/Fyn interactions.

    4. PTZ transiently increased PSD-95/tau/Fyn complex formation in p38γ+/+ animals; this effect was even more noticeable in p38γ−/− mice

      p38y was shown to inhibit the formation of complexes, but the addition of PTZ lowers the protective function of p38y.

    5. PSD-95/tau/Fyn interaction was reduced in transgenic mice with neuronal expression of p38γCA

      The interactions that are required to form the complexes are reduced in mice with an active form of p38y, demonstrating that p38y may prevent complex formation.

    6. PSD-95 copurified more tau and Fyn from p38γ−/− versus p38γ+/+ brains, and even more from APP23.p38γ−/− compared with APP23.p38γ+/+ and p38γ−/− brains

      An immunoprecipitation for PSD-95 was ran. The proteins that were associated with PSD-95 complexes also precipitated due being in a complex with PSD-95. The results show that tau and Fyn were contributing more to the PSD-95 complexes when p38y was not present.

    7. PSD-95/tau/Fyn interaction was enhanced in Alz17.p38γ−/− animals versus Alz17.p38γ+/+ mice

      Results show that more PSD-95/tau/Fyn complexes were in the brains of p38𝛾-/- vs. p38𝛾+/+. This shows that PSD-95/tau/Fyn complexes are associated Amyloid-beta induced excitotoxicity

    8. when compared to tau−/−.p38γ+/+mice, tau−/−.p38γ−/− animals showed similar protection from PTZ-induced seizures

      p38y only protects agianst PTZ-induce siezures only when tau is present. A difference between p38y being present and p38 being absent is only seen in mice that have tau.

    9. These data also showed that, compared with APP23 mice, APP23.p38γ−/− animals had aggravated memory deficits that persisted with aging

      APP23.p38y+/+ mice survived longer and had performed better in water maze than APP23.p38y-/- mice. Also shown in the results is that APP23.p38y+/+.tau-/- vs. APP23.p38y-/-tau-/- mice, are statistically the same, suggesting that the protective effect of p38 comes from phosphorylating tau.

    10. The exacerbating effects of p38γ loss on reduced survival, memory deficits, and neuronal network dysfunction of APP23 mice were virtually abolished in APP23.p38γ−/−.tau−/− mice

      The APP23 deficits improved when tau was not present in mice.

    11.  p38γ−/− mice showed no deficits and had normal motor function

      The lack of p38y kinase did not negatively affect the movement and motor function of the mice.

    12. Aβ pathology was comparable in the brains of APP23.p38γ−/− and APP23.p38γ+/+ mice (fig. S6), but p38γ deletion aggravated premature mortality and memory deficits of APP23 mice

      APP23 mice that had p38y and did not have p38y displayed similar traits, but the deficits in mice that did not possess p38y kinase were worse.

    13. Surprisingly, only p38γ depletion (p38γ−/−), but not systemic p38β, p38δ, or neuronal p38α (p38αΔneu) knockout, changed PTZ-induced seizures

      The only knockout mouse that displayed a change associated with PTZ-seizures was p38y. Because p38y was the only one that influenced the results, it is the focus of all the experiments.

    14. Finally, we found that tau-dependent Aβ toxicity was modulated by site-specific tau phosphorylation, which inhibited postsynaptic PSD-95/tau/Fyn complexes, revealing an Aβ toxicity–limiting role of p38γ in AD that is distinct and opposite to the effects of p38α and p38β (11, 13, 14).

      The authors state, contrary to popular belief, that tau can play a protective role in limiting amyloid beta toxicity by interacting with p38γ. By phosphorylating specific sites tau can increase neuron survival and improve memory loss.

    15. PTZ-induced seizures are reduced in tau−/− mice (8, 9). Adeno-associated virus (AAV)–mediated expression of WT and T205A neurons, but not T205E tau or green fluorescent protein (GFP), in the forebrains of tau−/− mice enhanced PTZ-induced seizures (Fig. 4D and fig. S25).

      The data shows that the tau-/-.AAV tauWT and tau-/-.AAV tauT205A were the most susceptible to seizures and had the most severe seizures out of the four genotypes.

    16. Hence, phosphorylation of tau at T205 should similarly mitigate neurotoxicity. Aβ caused cell death in WT and T205A neurons but significantly less in T205E tau-expressing neurons (fig. S23). Similarly, neurons expressing p38γ and, more so, p38γCA were significantly more resistant to Aβ-induced cell death than controls (fig. S24).

      The results from previous experiments showed that neurons survived at higher rates when they had T205E and p38γ.

    17. Pan-p38 inhibition stopped p38γ/p38γCA-induced disruption of PSD-95/tau/Fyn complexes

      If p38y is completely inhibited, the complexes are stable.

    18. Hence, p38γ regulated PSD-95/tau/Fyn complexes via phosphorylating tau at T205.

      The results of this experiment showed that p38γ helped to disrupt the PSD-95/tau/Fyn complexes through phosphorylation of T205.

    19. Increasing p38γ levels compromised PSD-95/tau/Fyn interaction in cells, and expression of a constitutively active p38γ variant (p38γCA) completely abolished this interaction

      p38y was shown to prevent the interactions required to form the complexes associated.

    20. Similarly, pT205 was markedly reduced in APP23.p38γ−/− animals compared with APP23.p38γ+/+ mice (Fig. 4B)

      The results of the previous experiment showed that APP23p38𝛾-/- mice had decreased T205 phosphorylation compared to the APP23p38𝛾+/+, which had T205 phosphorylation.

    21. no PSD-95/tau/Fyn complexes were isolated from tau−/− and tau−/−.p38γ−/− brains

      Demonstrates that the complexes will not form if unless tau is present.

    22. In summary, the levels of active p38γ kinase and tau phosphorylation at T205 determined susceptibility to excitotoxicity and Aβ toxicity.
    23. the effects of p38γ on excitotoxicity and Aβ toxicity were tau-dependent.

      The protective qualities of p38y are dependent on tau being present. If tau is not present, amyloid-beta toxicity effects the cells the same, even if p38y is present.

    24. increasing tau levels in p38γ−/− mice [brought about by crossing with nonmutant tau-expressing Alz17 mice (23)] significantly enhanced PTZ-induced seizures in Alz17.p38γ−/− mice

      Mice that had higher levels of tau were more susceptible to seizures.

    25. In summary, p38γ depletion exacerbated excitotoxicity, neuronal circuit synchronicity, mortality, and memory deficits in APP23 mice, without changes in Aβ pathology.

      Overall, every deficit associated with APP23 was made worse when p38y was not present.

    26. Electroencephalography showed enhanced spontaneous epileptiform activity and interictal hypersynchronous discharges in APP23.p38γ−/− compared with APP23.p38γ+/+ mice

      From the results, the researchers can infer that the presence of p38𝛾 kinase has a protective ability that lessens the amount of seizure trains that occur due to Aβ density bodies

    27. Compared with APP23.p38γ+/+ mice, APP23.p38γ−/− animals had increased sensitivity to PTZ-induced seizures

      From the results conducted in the experiment, specifically the Fig. 1 G-J, mice that did not possess p38y were more sensitive to seizures

    28. only p38γ localized to postsynapses and limited excitotoxicity.

      The only knockout mouse that was shown to cause a change in PTZ-induced seizures was p38𝛾. p38𝛾 was also the only kinase that was shown to localize in postsynapses between neurons.

  6. Nov 2017
    1. mimicking site-specific tau phosphorylation alleviated Aβ-induced neuronal death and offered protection from excitotoxicity.

      The site that is phosphorylated by p38y was found to be important for reducing effects of AD. Demonstrates that the function of p38y is important, and the mere presence of p38y in the cell is not protective, it has to be functional.

    2. depletion of p38γ exacerbated neuronal circuit aberrations, cognitive deficits, and premature lethality in a mouse model of AD, whereas increasing the activity of p38γ abolished these deficits

      The research found that the presence of p38y reduced the effects of AD in the mouse model.

    1. first, the sex-determining proteins studied in the present work evolve at constant rates, as suggested by global molecular clock tests (Table 1).

      From Table 1, the following sex-determining proteins display InL, InL(clock), and the p-value. These factors display the final calculations. From what the author first concluded, the InL(clock) values show that there is in fact a constant rate with which the proteins evolve. It is tested by the likelihood ratio tests based off the models of evolution defined. -Melanie

    1. The high levels of genetic differentiation detected within C. jimenezii raise questions whether these two populations can be treated as different varieties/subspecies within this taxon or if indeed they may represent two different species.

      In this study, the researchers found some questions as to whether the two species of C. jimenezii could be grouped with the same taxa.

      Upon meeting with the author, it was stated that the molecular tools used, found a large amount of differentiation. This was not what the authors hoped and in turn was concluded that they were to remain in separate taxa.

      RA

    2. Therefore we recommend not translocating material between these two populations for genetic conservation or ecological restoration programs until the taxonomy of this species within Coccothrinax is further studied.

      Genetic conservation of this population is important due to the few individuals left in Haiti and the Dominican Republic.

      Upon meeting with the author, the difficulty of finding the purebred species was discussed as were the methods.

      RA

    3. The taxonomic uncertainties between the two populations of C. jimenezii have important implications for reintroduction programs. These two sites of C. jimenezii represent two clear management units for conservation, and the population genetic data suggest that we cannot rule out that they are two distinct taxa.

      The authors concluded based off of the molecular data, that the two species of C. jimenezii could not be identified as two different taxa.

      RA

    4. We have not been able to find data regarding the environmental history in these two populations since the 15th century. However, there is agreement among conservation biologists that since the arrival of the Europeans to this island there has been habitat fragmentation and deforestation linked to rapid expansion of urban and rural activities (Sambrook et al., 1999; Alscher, 2011; Foxx, 2012). Palms have long-life cycles; therefore, the detrimental consequences of genetic drift on genetic diversity can take a long period of time to manifest because of their long generation time and the presence of overlapping cohorts (Duminil et al., 2009).

      Since the extinction of C. jimenezii is of primary concern, the authors grab resources from other works to help solidify this concept. It is clear that the conservation of this species is vital to this study.

      RA

    1. The answers to fundamental questions about the origins of animal life and the evolution of their diverse phenotypes may be held in the genomes of distinct invertebrate phyla.

      The conclusion explains why they investigated what standards an invertebrate must reach to be tested for a successful genome sequencing. The researchers also add that geneticists could choose another option than searching an organism that meets their criteria. This option is sequencing organisms and modeling them for another organism. This would allow the geneticist to understand the other organism by having an idea of how the genome functions.

      The researchers also state a challenge faced by the science community is understanding the data they collect from the genome sequence, apart from also gathering the sequences. They state the research they do will help advance knowledge about invertebrate genomes by providing the necessary tools to investigate the sequences. (NAJ)

    1. Likewise, there is no evidence for differences among the pairs in historical effective population sizes or generation times that can be related to divergence (20).

      The generation types (ex. F1, F2, etc.) and population size were taken into account for each shrimp pair. These factors were found to not support the phenomenon of divergence among shrimp pairs because no differences were found. ~J.D.A.

    2. Our data can also be used to estimate rates of divergence in reproductive compatibility.

      The less compatible they are the more they have diverged. ~S.Z.

    3. Pacific members of the most divergent pairs are found deeper in the intertidal or are rare in habitats with heavy sedimentation (25) (Fig. 2). Thus, larval avoidance (26) of shoaling waters over the rising isthmus (6, 7) may have accelerated genetic isolation of these pairs.

      The shrimp located closer to the sea floor had a slimmer chance of being pushed over the isthmus; therefore had a higher chance of isolation and divergence. ~S.Z.

    4. However, they do show some distributional differences that could affect sensitivity to changing conditions associated with gradual rise of the isthmus.

      The physical location of the shrimp could effect the divergence associated with the gradual rise of isthmus. ~S.Z

    5. The null hypothesis, that isolation was simultaneous but rates of divergence are highly variable, is incompatible with the observed pattern because metabolic enzymes, mtDNA, and mate recognition share no mechanistic basis that would cause their divergence rates to be automatically associated.

      Basically, the null is rejected because it contradicts the observed data. The null states that isolation occurred around at the same time, but the observed data shows divergence indicators such as metabolic enzymes, mtDNA, and mate recognition, all of which are not associated at a single mechanistic basis required for concurrent divergence. ~S.Z.

    6. Geographic isolation is thought to permit divergence and speciation by disruption of gene flow

      The physical barrier created by the Isthmus of Panama prevented the exchange of genes; therefore, allowing the organism to develop differently on wither side of the barrier or diverge. (SZ)

    7. All the shrimps we studied are shallow water, fully marine forms with planktonic larvae.

      Main subjects studied. Planktonic larva is significant in this study because larva shrimp would migrate to different regions of the Isthmus of Panama which may be a significant contributor to speciation events ~J.D.A. (+ JP)

    8. Fig. 2

      In general, this graph illustrates that as genetic distance between species increases (this is measured by Nei's D) then mtDNA divergence increases as well. Overall, compatibility between two different organisms will be less if they have high mtDNA divergence and a high Nei's D value. (JP)

    9. Table 1

      mtDNA CO1 is a gene found within the mitochondria, it is used to measure the genetic difference between organisms. A higher mean indicates a larger difference between two organisms, which is indicative of being a different species. (JP)

    1. Energy intake and thermal excess were positively correlated with body size as measured by the curved fork length (CFL) of tagged tunas

      A big tuna (large body size) requires more energy which means it needs to feed from a higher amounts of prey or big preys. Consequently, the heat production is higher provoking a thermal excess. YS & WT

    2. Lower energy intake was observed during late summer (August and September), when bluefin tuna are moving up through the Southern California Bight (28° to 32°N).

      Lower energy intake during migrations - M.A.S

    1. Management of nutrient effects on both of these pathways would positively affect riverine health.

      The purpose of these experiments were to test the effects of nutrients on terrestrial carbon loss that ultimately leads to a change in ecosystems.

      Learning the effects and ideal ratios of nitrogen to phosphorus for ecosystems will lead to better policies to protect them.

    2. Litter quantity in the streambed was predicted to be 2.8 times and 7.7 times higher in reference versus nutrient-enriched streams after 6 and 12 months,

      In the experiment, it was found that the addition of nutrients encouraged terrestrial organic carbon loss.

      This was tested by observing the litterbags of the experimental streams and comparing the data to the litterbags of the control stream.

      Since a large amount of mass was lost in the stream with nutrient additions, this gives some evidence that too many nutrients off-balances organic carbon levels.

    3. Reach-scale outputs of C increased as fine POC export, as well as respiration (15).

      Fine POC export represents the movement of broken down carbon along the stream. Finer particles move faster and further down a stream as biological factors such as microbes and fungi decomposing the terrestrial organic carbon.

    4. They may limit terrestrial C loss as CO2 and maintain downstream C export, but contribute to depletion of local C resources (22, 23).

      Detrivores have a different method of carbon depletion from streams. finer particulate organic carbon travels faster and further away from an area, deleting the area of carbon sources.

      Invertebrates may leave the system if there are no food sources and alter the food chain.

    5. However, roughly similar-sized effects of N and P on loss rates are strong evidence of co-limitation (Fig. 2 and table S3).

      Both nitrogen and phosphorus are contributing factors to changes in terrestrial carbon loss.

      Within the ecosystem, different organisms require different ratios of nutrients to react and convert terrestrial carbon to carbon dioxide.

    1. Another study in which mouse NC cultures were treated with Edn3, Edn1, or Kitl showed an increase in the number of melanocyte progenitors; however, Kitl alone was not sufficient to induce the differentiation of melanocyte progenitors into mature melanocytes. Mature melanocytes were however observed, when treatment with Kitl was followed by Edn3 or Edn1 (Reid et al., 1996). As previously noted, although in the absence of Edn3, Kit-positive and DOPA-positive cells arose in mouse NC cultures, Ednrb signaling was required for the generation of fully pigmented melanocytes (Ono et al., 1998). These findings hint to a specific requirement for Ednrb signaling, independent of Kit signaling, in melanocyte differentiation. This requirement for Ednrb in the final phase of melanocyte differentiation may occur cell-autonomously, as suggested by the inability of Ednrb null cells to generate pigment even in the presence of Kitl (Hou et al., 2004). Together these findings point at a cooperative interaction between Kit and Ednrb signaling in melanocyte development, with Ednrb signaling being specifically required in the final differentiation step

      This paragraph discusses how Ednrb is needed in order to further a melanocyte into melanoma, even if Kitl (another signaling pathway) is present. Therefore, this is the direct link to melanoma.

      (NB)

  7. Oct 2017
    1. Table 2

      By quantifying behavioral tolerance and intolerance of male-female transisthmian pairs, the researchers are able to compare interactions between closely related and distantly related species of snapping shrimp.

      For example, while keeping figure 1 and table 2 in mind, more closely related species have higher compatibility compared to more distantly related species. Although this is not an indicator of having viable offspring, this shows that closely related species may share similar behaviors or may have similar niches. (JP)

    2. Fig. 1 Single most parsimonious phylogenetic tree constructed on the basis of mtDNA sequences with PAUP (18). Transitions were given one-quarter the weight of transversions (based on the fourfold greater abundance of transitions than transversions in our data), and trees were rooted by the P7-P7'-C7 clade. Taxon codes are as in Table 1.

      Figure 1 is a visual representation of the relationship between differing species of snapping shrimps. This diagram was made using the mitochondria DNA sequences of the organisms and the PAUP program which calculates the level of relatedness between the sibling species of snapping shrimp.

      Comparing Table 1 with Figure 1, it is found that species more closely related, such as P2 and C2, had a lower mtDNA mean value (6.6). Meanwhile, species that were more distantly related, such as P7' and C7, had a higher mtDNA mean value (19.7). (JP)

    1. our findings suggest that the overexploitation of spawning aggregations can fundamentally alter the natural predator-prey equilibrium, limiting foraging options for reef sharks within aggregation sites.

      The inverted biomass pyramid is a good thing, but the fish spawning aggregations play an important role in whether or not this stays a good thing.

      • D.N.B.
    2. These observations confirmed that hundreds of sharks actively feed on a large variety of prey (at least 14 fish species; Figures 4 and S3). In particular, sharks feed aggressively on the large number of groupers present during spawning aggregations in June and July [13]. Shark abundance and residency times both increase when camouflage groupers (Epinephelus polyphekadion) arrive from the surrounding reef area to spawn

      there is an active correlation between the populations of prey and predators, when the camouflage groupers aggregate in order to spawn. This increase in prey is what attracts the sharks. MSARS , WT & YS

    3. Overall, sharks showed different degree of residency (mean ± SEM = 42.21% ± 7.75% of days present in the pass; range = 2.1%–95.9%; Table S3), with three transient (<20% residency), six semi-resident (20%–70% residency), and four highly resident (>70% residency) sharks (Figure S2).

      The study showed that overall, there was a higher number of sharks observed that spent most of their time in the pass than there were that spent less of their time in the pass. YS & WT

  8. Aug 2017
    1. Western assay of induced SX4 cells showed the presence of Venus only in the membrane fraction and not in the cytoplasmic fraction, suggesting efficient membrane localization of Tsr-Venus.

      The e coli strain engineered by the authors is behaving as they predicted.