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Memory study weaknesses

Submitted by jhussaini on Wed, 04/24/2019 - 15:16

The weaknesses of this study involve the mortality rate of their test subjects. I was shocked to hear in class that somewhere around 25% of the mice died during testing from seizures. This makes sense considering they are just activating a whole bunch of neurons with a simple injection. It makes me wonder whether this could be effecting the behavior of the mice that did survive the experiment. For example, could their fear response with and without CNO be a natural anxiety developed from brain damage from the experiment? Secondly, the results from Fig 1D are somewhat concerning as it takes about an hour for the mice to respond to CNO which could mess with results. Additionally, the results rarely ever revealed over a 50% freezing which are nor very strong results.  Despite that, because of their control experiments, and logical experimental outline, the results are still valid, just not as strong as we could hope for.

marine diving adaptations

Submitted by jhussaini on Tue, 04/23/2019 - 13:32

When marine mammals dive into deep, high pressurized waters, they experience an increase in dissolved nitrogen gas in their bloodstreams. The dissolved gas poses a threat because if the divers ascend too fast, they experience a phenomenon known as the “bends,” whereby gas bubbles form inside the body and increase the risk of contracting decompression sickness. Fortunately, marine mammals have a special lung architecture that creates two different pulmonary regions to combat high-pressure depths. They have a compressible chest that limits the amount of nitrogen gas that can be absorbed. The authors of the review article suggest that the physiology of diving mammals is poorly understood, and that there are other cardiorespiratory mechanisms that provide a better explanation for their ability to dive deeply. The results of the paper showed that many marine mammals can withstand high levels of nitrogen gas that would normally cause decompression sickness 50% of the time. The authors also hypothesized that parasympathetic stimulation helps limit lung perfusion, which is a necessary for diving to great depths. They propose that high amounts of stress can interfere with this process and might explain the failure of a normal dive response. Overall, these findings are significant because they offer a new perspective on the physiological and respiratory adaptations that enable cetaceans to dive at great depths. 

diving mechanisms paper

Submitted by jhussaini on Tue, 04/23/2019 - 13:32

When marine mammals dive into deep, high pressured waters, they experience an increase in dissolved nitrogen gas in their bloodstreams. The dissolved gas poses a threat because if divers ascend too fast, it can lead to a phenomenon known as the “bends,” whereby gas bubbles form inside the body and can potentially cause decompression sickness. Fortunately, marine mammals have special lung architecture that creates two different pulmonary regions to combat high-pressure depths. They have a compressible chest that limits the amount of nitrogen gas that can be absorbed. The authors of the review article suggest that the physiology of diving mammals is poorly understand, and that there are more cardiorespiratory mechanisms that provide a better explanation for their ability to dive deeply. The results of the paper showed that many marine mammals can withstand levels of nitrogen gas that would normally cause decompression sickness 50% of the time. The authors also hypothesized that parasympathetic stimulation helps limit lung perfusion, which is a necessary for diving to great depths. They propose that stress can interfere with this process which might explain failure of a normal dive response. Overall, these findings are significant because they offer a new perspective on the physiological and respiratory adaptations that enable cetaceans to dive at great depths. 

paper results2

Submitted by jhussaini on Mon, 04/22/2019 - 00:31

The authors first cloned melanopsin cDNA in rat cells to show that the protein sequence is nearly identical to that of mice. Then they generated specific antibodies targeting melanopsin to show the subset of cells that contained the protein. Tau-lacZ targeting shows the projections of melanopsin positive cells to the SCN and other regions of the brain. Lastly, they used a combination of immunofluorescence and Lucifer Yellow to show that intrinsically photosensitive RGC’s were melanopsin positive. Figure 3 shows that the authors targeted the tau-lacZ gene locus RGC’s and used immunofluorescence in mice. The structure of melanopsin positive cells was similar to that in rats. X-gal labeling not only showed retinal labeling of axons, cell bodies and dendrites, but it also showed B-galactosidase activity in parts of the brain such as the SCN, the olivary pretectal nucleus, the dorsal lateral geniculate, and other parts of the brain. This finding suggested that melanopsin positive cells are involved with processing information that is relayed to the brain.

results

Submitted by jhussaini on Mon, 04/22/2019 - 00:30

The experiment showed that melanopsin is the photopigment present on specific RGC’s that is likely to be involved in photoentrainment. Figures 1 and 2 show melanopsin positive RGC’s using immunofluorescence in rats. Melanopsin positive cells were only about 1% of the total number of RGC’s, and only a few of the melanopsin positive cells are found in the inner nuclear layer while the rest are in the ganglion cell layer. Confocal, stained images as well as digital images of melanopsin positive RGC’s were generated. The data from figures 1 and 2 showed the abundance of melanopsin on the dendrites, axons, and cell bodies in addition to the shape and structure of RGC’s. 

more synapse

Submitted by jhussaini on Fri, 04/19/2019 - 13:41

The authors use both mice and rats in their experiment. Mice are used because their genome is largely similar to the human genome. Rats were used because their genome is 92% similar to mice. Rats were also used because they are larger than mice, which makes them a good model organism for examining retinal circuitry. The authors first cloned melanopsin cDNA in rat cells to show that the protein sequence is nearly identical to that of mice. Then they generated specific antibodies targeting melanopsin to show the subset of cells that contained the protein. Tau-lacZ targeting shows the projections of melanopsin positive cells to the SCN and other regions of the brain. Lastly, they used a combination of immunofluorescence and Lucifer Yellow to show that intrinsically photosensitive RGC’s were melanopsin positive.

Synapse

Submitted by jhussaini on Fri, 04/19/2019 - 13:40

The objective for this study is to understand the mechanism of non-visual reflexes such as regulation of the circadian clock and pupillary reflexes. The suprachiasmatic nucleus (SCN) is a site for photoentrainment in the brain. A portion of light-sensitive retinal ganglion cells protrude into the SCN. The authors hypothesized that melanopsin is a photopigment on the retinal ganglion cells (RPG’s) that generate action potentials to the brain in response to light, and play a role in photoentrainment. Although it was known that some RPG’s are photosensitive, the reasons for this phenomenon were unknown. It was also known that rods and cones are not photoentraining receptors. Provided this context, the reason for the study was to understand the function of RPG photosensitivity, and to use them to study the pathway that gives rise to photoentrainment.

structure of paper

Submitted by jhussaini on Wed, 04/17/2019 - 17:19

The publication by Abrams has a level 2 heading whereas the other one has a level 1 heading. The paper by John and Dale is structured more like a lab report following an experiment. It includes labeled figures, tables, and headings such as “abstract” and “results.” The publication by Abrams is structured more like a question-and-answer paper written in an essay format. The questions are bolded with long paragraphs that follow in response. The first paragraph of both publications gives an overview of the objective in addition to brief background information. The publication by Abrams has multiple in-text-citations in every paragraph whereas the publication by John and Dale has few in-text citations. The publication by Abrams also has many more references than that of John and Dale. This makes sense to me because the goal of the publication by John and Dale is to add new knowledge to Ecology, whereas the goal of the other paper is to present the knowledge in an understandable way. The format of each publications is tailored to its objective.

Hh signalling

Submitted by jhussaini on Wed, 04/17/2019 - 17:15

Although all of these developmental malformations impact the Hh signaling pathway in some way, they give rise to different phenotypes. These differences are visual indicators of different ways the Hh pathway can be disrupted. By discerning the gene that causes each syndrome and the molecule(s) that are disrupted as a result, you can figure out the role that the disrupted molecule normally plays in the pathway. For instance, based on the syndromes described above, you can infer that the Hh signaling pathway is responsible for eye and brain development. Knowledge of related abnormalities caused by disrupting a single pathway can elucidate the function of multiple components in the pathway and how those components interact with one another.

limb malformations

Submitted by jhussaini on Wed, 04/17/2019 - 17:14

Malformations in the SOX9 gene can result in a variety of syndromes including Pierre Robin Syndrome, Campomelic Dysplasia, and Acampomelic Campomelic Dysplasia. In Greek, Campomelic means “bent limb,” which is a common symptom of Campomelic Dysplasia. Individuals born without bowed limbs are said to have Acampomelic Dysplasia. Both syndromes involve skeletal and reproductive malformations and are life-threatening in newborns. Malformations in the Hh signaling pathway can cause Holoprosencephaly, Microphthalamia with Coloboma, and Schizencephaly. Holoprosencephaly is an abnormality in brain development when the prosencephalon does not divide into the left and right hemispheres. Microphthalmia occurs when one or both eyeballs is abnormally small. People with Microphthalmia often have Coloboma, an anatomic abnormality in which pieces of tissue are missing from the eye. Finally, Schizencephaly is a rare birth defect that causes clefts in the cerebral hemispheres of the brain.

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