Animal Movement Article Summary 2

Submitted by brdougherty on Thu, 11/09/2017 - 22:06

In order to test his hypothesis Biewener made different sized mammals run on a force platform where he filmed the mammals in lateral view in order to determine the mechanical advantage of the ground reaction force in relation to the moments exerted at the joints that corresponded. To determine the mechanical advantage of the extensor groups Biewener used radiographs or anatomic dissection, and adjusted for observed angular displacements at joints. Once the mechanical advantage for both of these were found the EMA of extensor muscle was calculated for the joints of the forelimb and hindlimb when the limb was in contact with the ground.

            The results in Biewener’s experiment show that the peak stresses in the muscle are relatively uniform in mammals of varying body sizes. In fact the results show the EMA scales almost proportional to body mass. The results also show that there was no significant change in EMA when a species was changing gates or moving at varying speeds. These results support Biewener’s theory that limb posture would adjust when species got larger to a more upright position in order to have similar stresses act upon joints as smaller mammals

Neurobio Paper 2 Draft

Submitted by samihaalam on Thu, 11/09/2017 - 21:27

1. What is the objective/hypothesis/question of this study? 

  • melanopsin is a visual pigment 
  • how is this signal transmitted to the brain?

2. What is the rationale/relevance of this question?

  • found that melanopsin goes to SCN 
  • studied mice that lack rods and cones to see if hey have photosensitivity
  • how did they know circadian clock is associated with the eyes?
    • mice without eyes can't reset their circadian clock
    • mice without rods and cones, mice that are blind, can still reset their clocks 

3. What system are the authors using to answer this question? Why?

  • mice 
    • similar to rats 
    • small
    • transgenic mice! - can easily put their lacZ gene in the mice and test them out, not a lot of other models can do dat 
  • rats
    • maybe because they're bigger than mice, yet still comparable 
    • maybe because they had more experinece/better at handling the rats

4.  What methodological approach has been used? 

  • make antibody, then make the protein from that → use rabbits, then take out of rabbits 
  • tested a bunch of parameters: where the cells are, etc
  • immunochemistry with the antibodies → only see stains in the retina
  • add lacz → when it binds, it turns blue
    • bound to the protein that  takes it to the axons and dendrites 
    • only see it in retinas, not axons?
  • if see it projecting to SCN, now have mechanism to find controls for circadian rhythm
  • inject with Lucifer yellow, measure membrane potential, use antibody
  • inject dye in SCN (Luc - yellow) --> project backwards --> called backfill!! 
    • projects backwards into the retina and see if those cells contain melanopsin positive --> shows that in those cells, melanopsin is definitely involved in this mechanism
    • if backfill found 1/2 the cells that go to SCN are melanopsin positive and 1/2 the cells are melanopsin negative, would suggest others,
    • BUT, this shows that all the cells that come from the SCN are melanopsin positive! 

Acclimating planaria

Submitted by vthong on Thu, 11/09/2017 - 18:52

Before being distributed to their assigned groups, we will acclimate the planaria to their respective environments. All 90 planaria will be placed in Poland Spring water for one day prior to being placed into increasing concentrations of the three varying environments. If we observe that the planarians die in the process of being acclimated in higher concentrations of solute, then we will decrease the experimental concentrations so that the planarians will survive the duration of the experiment. Once acclimated, each group will receive planaria for both their control and given environmental groups.


Persuasive statement Perfect paragraph

Submitted by briangriffin on Thu, 11/09/2017 - 18:45

              The breed of dog that should be given the vaccine is a husky. This type of dog should be saved because it is a relatively healthy. Many breeds of dogs have gone through tight bottlenecks over the past hundred years, which has led to many shared recessive diseases and phenotypic mutations. Huskies do not possess many of these phenotypic mutations such as stunted growth and a compressed face. Huskies are most phenotypically similar to the ancestors of all dogs. This provides us evidence that huskies contains a healthier genome than any other breed of dog. And with this healthier genome a bottleneck of one dog will lead to a better future population of dogs than any other breed.

Animal Movement Article Summary

Submitted by brdougherty on Thu, 11/09/2017 - 16:45

            In the article, Scaling Body Support in Mammals: Limb Posture and Muscle Mechanics, Biewener examines the effects of body structure on peak stresses.  In theory the way bones scale and the muscle geometry of mammals suggest that peak stresses should increase with increasing size. However, if this statement were true then large animals would be functioning near the limit possible for the skeleton which research shows is untrue. Research shows in fact that when mammals ranging from 0.1 to 300 kg were tested doing strenuous activities that their peak skeletal stresses were fairly uniform and their safety factor ranged from a 2 to 4.  In order to explain this Biewener proposes “that similar stresses are achieved in the mammalian skeleton by a size-dependent change in locomotor limb posture, shifting from the crouched postures of small animals to the more upright postures of larger species.” The thought process behind this theory was originally recognized by Gray, who noted that a more upright position would align the segments and joints in the limb more with the ground reaction force vector, exerted at the foot. This transformation would vastly reduce the moments exerted on the joints of the limbs. 

Planarian Sensory Organs

Submitted by alexispena on Thu, 11/09/2017 - 15:22

Although basic, planarians have been shown to exhibit decision making behavior. Planarians are able to process external stimuli by their sensory organs, eye spots and auricles. The eyespots are located on the head of the planarian, and are used to detect light. The behavior in response to the change in light is called phototaxis. Planarians exhibit negative phototaxis, moving away from the light source. Auricles are on the side of the planarians head, and contribute to its triangular shape. The auricles contain chemoreceptors which respond to chemical stimuli. The auricles can play a role in finding food or the detection of changes in habitat.

Trimyristin mass and TLC plate

Submitted by daniellam on Thu, 11/09/2017 - 13:59

The original mass of the nutmeg was 4.013 grams. After the extraction, the mass of the trimyristin was 0.186 grams. The percent recovery of the trimyristin was rather low, only 4.63%. This was an expected value because it was an extraction of nutmeg.

The TLC plate indicates that the product was not pure.  It showed a streak that went from the baseline of the plate to about a third of the plate where it begins to dissipate.  The Rf value of the trimyristin is 0.36 and the Rf of the dissipating substance is 0.5.  The values are within the 0.2 to 0.5 range, however, there are two substances meaning it could be impure.  The streaking may be from putting too concentrated a sample onto the plate.  A possible solution for this would be to increase the amount of solvent, decreasing the substance’s concentration.

Perfect Paragraph 11/9

Submitted by dwiley on Thu, 11/09/2017 - 11:55

Planaria have been used for research on regeneration primarily because of their short regeneration time. However, one thing to consider is whether they regenerate at the same rate in all different types of circumstances. That is what this study set out to determine. In a two-week examination, students in the Fall 2017 Writing in Biology class with Steven Brewer will separate several planaria and put them in different light settings to observe whether light has an effect on regeneration rate.

Neuro Notes Chapter 13

Submitted by kmydosh on Thu, 11/09/2017 - 11:24
  • The structure of skeletal muscles
    • T tubules: spread excitation
      • Talking about calcium again
      • The calcium is in high ammounts inside the muscle
    • Muscle fiber is encased in a
    • Bottom line changes in volatage spread through the muscle fiber and open up ca channels and release calcium
    • Calcium release allows the actin and myosin fibers to slide against eachother
      • Heads of myosin walk along the actin in response to the calium
      • Calcium present allows the myosin to come into contact with the actin
    • The trigger is calcium and it is able to have its effect
    • Troponin
  • Proprioception
    • Sense of knowing where your body is in space
      • Two different sensors
        • Muscle spindles
        • Golgi tendon organs 

Physics Conclusion

Submitted by kmydosh on Thu, 11/09/2017 - 11:24

In this experiment we used probes to measure electric potential between two charged contacts and visualize electric fields. Various charges and directions were mapped with the two probes to map the electric field. To map equipotential lines five different points were located for 2V, 3V, and 4V. A pattern can be seen forming around the positive and negative contact points on the electric field board. Each point at an equipotential line has the same value. The patterns mapped on the board were consistent with the map of the electric field shown in lab. 


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