Histology staining of three dopamine-synthesizing sources in the hypothalamus support the findings in Figure 5E. The amount of TH cells (dopamine-synthesizing cells) in these regions decreases with 6-OHDA and can be partially rescued with short-day photoperiod exposure.

Even with 6'OHDA treatment, exposing the animals to short-day photoperiod resulted in some behavioral rescue, reflected by the animals spending more time spent in the open arm in the EPM test and less time spent immobilized in the forced swim test. The difference in behavior is significant comparing results of the short- vs long-day photoperiod exposure. One additional comparison that could be insightful are the results of 6'OHDA on 12L:12D photoperiod exposure; these can be found in Figure 5 B, and do not appear to be significantly different from the long-photoperiod exposure results. Thus, a follow up idea for the researchers is to consider when the effect of increasing the duration of light-exposure in a day begins to saturate.

Here, dopamine synthesis is being stopped by two things: the neurotoxic agent 6-OHDA and long-day light exposure, a stressor for nocturnal animals. Both treatments should reduce the presence of dopamine-making neurons.

These findings validate the specificity of 6-OHDA's delivery. In the dopaminergic cell group A13 just 200 μm away from the treatment site, the effects of 6-OHDA are not observed.

Following action potential firing, transmitters will be sent from the presynaptic, or sending, neuron to the postsynaptic, or receiving, neuron; the received transmitter will thereby alter the likelihood of that postsynaptic neuron firing its own action potential. The experimenters had observed that at certain clusters of neurons in the CNS, short photoperiod exposure increased production of the transmitter dopamine, and long photoperiod exposure led to an increased production of somatostatin. Consequently, the experimenters are questioning whether expression of those cognate postsynaptic receptors, i.e., dopamine receptors or somatostatin receptors, follow suit.

For rats, nocturnal mammals, increased photoperiod exposure is a stressor. Consequently, in both the EPM and FST, rats exhibit more depressive/anxious behaviors following long photoperiod exposure. In the EPM test, these rats spend less time in the open arm, and in the FST, they give up swimming and become almost immobile much sooner than the control group. For the short-day exposure group, the rats have more open arm activity, and in the FST persevere for longer, indicating reduced anxiety relative to the control group.

When expression of a receptor is greater than that of its transmitter, the likelihood of those transmitters binding to the receptor will be high. Thus, if levels of SST2/4R are high compared to the presynaptic SST, then presynaptic SST will likely be able to bind to the cognate receptor, and induce its inhibitory effects.

A decreased amount of TH-IR neurons means that less dopamine is being produced; this was observed when the rats were given long-day exposure (19 hours of light, 5 hours of darkness). Short-day exposure (5 hours of light, 19 hours of darkness) resulted in the number of TH-IR neurons increasing, a sign of greater dopamine production. These results were all relative to the control group, rats that experienced a balanced-day with 12 hours of light and 12 hours of darkness.

It is known that the young developing brain is able to add or switch the transmitters that their neurons express. The question guiding this research is whether sensory stimuli can cause the already mature (adult) brain to experience changes in the types of transmitters that are produced by their neurons.

Hydrology is the main reason for the carbon balance of wetlands by controlling the uptake of CO₂ and CH4. Determining the effect of droughts on CO2, fluxes and CH4 emission was stimulated by hydroperiod with three scenarios. These three scenarios affect the rate of drought from being gradual, intermediate, and rapid transition into drought. It resulted in higher net CO2 losses net ecosystem exchange (NEE) over a 22-week manipulation. Due to drought vegetation dieback, it increased ecosystem respiration (Reco), and it also reduced carbon uptake gross ecosystem exchange (GEE). The NEE did not offset methane production during periods of flooding. Changes in precipitation patterns and drought occurrence altered the carbon storage of freshwater marshes. We can determine that with the change in the climate will modify the storage capacity of freshwater marshes by influencing the water availability.

Connects to AP Chemistry Learning Standard 6: Any bond or intermolecular attraction that can be formed can be broken. These two processes are in dynamic competition, sensitive to initial conditions and external perturbations.

Found on page 71 of the AP Chemistry Course and Exam Description:

http://media.collegeboard.com/digitalServices/pdf/ap/ap-chemistry-course-and-exam-description.pdf

Connects to AP Chemistry Learning Standard:2.B

Forces of attraction between particles (including the noble gases and also different parts of some large molecules) are important in determining many macroscopic properties of a substance, including how the observable physical state changes with temperature

Found on page 27 of the AP Chemistry Course and Exam Description:

http://media.collegeboard.com/digitalServices/pdf/ap/ap-chemistry-course-and-exam-description.pdf

Connects to AP Chemistry Learning Standard:2.A.3: Solutions are homogeneous mixtures in which the physical properties are dependent on the concentration of the solute and the strengths of all interactions among the particles of the solutes and solvent:

Found on page 25 of the AP Chemistry Course and Exam Description:

http://media.collegeboard.com/digitalServices/pdf/ap/ap-chemistry-course-and-exam-description.pdf

CCSS.ELA-LITERACY.RST.11-12.8

http://www.corestandards.org/ELA-Literacy/RST/11-12/

Whenever an observation is not fully understood, scientists try to analyze the issue from different angles. Here, the authors observed that the inhibition of dynein wasn't sufficient for inhibiting the viral uncoating completely. Therefore, they deduced that other factors were implicated with uncoating and decided to explore this possibility.

Connect to Learning Standards: http://www.nap.edu/openbook.php?record_id=13165&page=69

Progression for explanation. In a previous study, the authors observed that HDAC6 was required for viral infection. As a consequence, they continued to study the function of HDAC6 in deep detail.

http://www.nap.edu/openbook.php?record_id=13165&page=43

Science can contribute to meeting many of the major challenges that confront society today, such as preventing and treating disease.