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How Polar Bears Survive Extreme Environments

Polar Extremes
Introduction: The Polar Bear (Ursus Maritimus) or more commonly known as the Ice bear. The Polar bear lives in the Arctic, a polar region located at the most northern part of the Earth. The Arctic consists of the Arctic Ocean, Iceland, Northern Canada, Sweden and other countries. Land within the Arctic region has seasonally varying snow and ice cover, with predominantly treeless permafrost-containing tundra. The Arctic region is a very unique area among the many of Earth’s ecosystems. (Wikipedia, Arctic, 2019)
The Polar Bear is found in the Arctic Circle and in adjacent land masses as far south as Newfoundland. Due to the absence of human development in its isolated habitat, it retains more of its original range than any other extant carnivore. While they are rare north of 88 degrees there is evidence that they range all the way across the Arctic, and as far south as James Bay in Canada. Polar bears are marine mammals because they spend many months of the year at sea, usually (3-5) However, it is the only living marine mammal with extremely powerful, large limbs and feet that allow them to cover kilometers on foot and run very fast on land. Its preferred habitat is the annual sea ice covering the waters over the continental shelf and the inter-island Arctic archipelagos. These areas, known as the “Arctic ring of life”, have intensely high biological productivity compared to the deep waters of the high Arctic. (Wikipedia, Polar Bear, 2019)
Figure 1: The Arctic (northern most part of the Earth), retrieved from

Figure 2: Polar bear, retrieved from

Effect of Magnesium of The Bone Strength of Rat Bones

Magnesium is the fourth most abundant inorganic mineral in the body, and one of six macromolecules vital for growth. It is required in the human body for energy production, oxidative phosphorylation and glycolysis and has a major role in the structural development of bone. Magnesium can be found in green leafy vegetables such as spinach and kale, fruit, Legumes, nuts, seeds and seafood, all in which should be balanced within in the human diet in order maintain sufficient magnesium levels (National Institute of Health, 2018). A magnesium sufficient diet balances intracellular calcium levels which encourages osteoblast proliferation, which increases bone formation and replacement of damaged cells to help maintain bone mass and strength (Abed, E, Moreau, R, 2009). Magnesium has many cellular functions including the crystal formation in bone cells and is required in the metabolization and activation of Vitamin D. Deficiencies in both of these nutrients has been associated with skeletal deformities decreased bone density (Uwitonze, A.M, Razzaque, M.S, 2018). Vitamin D plays a vital role in bone strength as it promotes calcium absorption and bone resorption through osteoclast proliferation resulting in skeletal calcium and phosphate homeostasis (Reddy P, Edwards L,R, 2019).
The recommended amount of magnesium is 300mg to 500mg daily (National Institute of Health, 2018), however magnesium deficiency indirectly impacts secretion and activity of parathyroid hormone via decreased Vitamin D activation which can lead to secondary hyperparathyroidism. In turn this can result in reduced regulation of calcium level, thus reducing bone density and strength (Lips, P, van Schoor, N,M, 2011).

Studies show that insufficient magnesium intake can result hypomagnesemia and hypermagnesemia which may lead to an imbalance of resorption and deposition in the bone by osteoblast and osteoclast activity (Castiglioni, S, Cazzaniga, A, Albisetti, W, Maier, J.A.M, 2013). Low Magnesium intake also reduced osteocalcin synthesis due to lowered osteoblast proliferation and has a direct correlation to diminished bone volume and abnormal bone remodelling (Carpenter, T. O, Mackowiak, S.J, 1992). Furthermore, studies show that low magnesium intake can lead to damaged or deformed cartilage, matrix calcification and altered bone differentiation (Castiglioni, S, Cazzaniga, A, Albisetti, W, Maier, J.A.M, 2013). Thus, leading to bone fragility and susceptibility to fractures, both in which are associated with osteoporosis (Castiglioni, S, Cazzaniga, A, Albisetti, W, Maier, J.A.M, 2013). Studies also show that sufficient magnesium intake has a marginal correlation to bone mineral density. (Farsinejad-Marj, M, Saneei P, Esmaillzadeh, A, 2015)
Osteoporosis is common condition which impacts the bone strength through the loss of calcium, which is regulated by magnesium, and bone density, resulting in bone fragility and susceptibility to fracture. It is more common in the elderly, usually adults ages 50 and older, where bone mass is naturally deteriorating, however studies show that a lack of magnesium homeostasis can cause effects of osteoporosis in adults as young as 20 years old.
Conducting this research is important to raise awareness about the correlation of magnesium imbalance in the bone and its impact on bone strength and rigidity. This includes groups such as athletes, elderly, obese all in which could have altered magnesium levels which could increase the potential of bone fracture.

It is unclear, whether or not an increase in magnesium levels in the blood and bone can reverse the detrimental effects of decreased bone density and strength, which have been associated with osteoporosis, without conclusion that magnesium is a direct cause of osteoporosis. Current research shows that maintaining magnesium homeostasis is a prevention method rather than curative method (Reddy P, Edwards L,R, 2019). It is also unclear whether or not increased magnesium levels in the bone can be maintained without extracellular and intracellular processes, and magnesium’s impact on bone strength without said processes, thus making the parameters of this experiment essential to obtain valuable data regarding the chemical properties of magnesium and how they can continue to impact the bone without considering other factors such as calcium and vitamin D deficiency, hyperparathyroidism.
Human physiology is complex with many metabolic processes in order to obtain the most ethical and accurate results, rats are often used in place of humans in medical research. In comparison to humans, rat bones have a similar the anatomical structure and proportional sizes making them the most anatomically correct model for human experimental research (Annaccone, P.M, Jacob, H.J, 2009).
The research conducted will assess the tibia and femur of each rat will be used to include a variable, to determine whether or not tibia or femur is stronger, or whether the magnesium solution has more impact on one bone, over the
other. Furthermore, the left and right sides of each bone will be used to test for asymmetry. Finally, both sexes with be tested to analyse the impact of the magnesium solution on the strength of the bone on females in comparison to males. Research shows that males have larger skeletal size especially in the femur and bone mass, which will have an impact on magnesium absorption, in comparison to the small bone mass of the female bones (Nieves JW, Formica C, Ruffing J, Zion M, Garrett P, Lindsay R, Cosman F, 2009). The bones size will also impact the strength and thus normalisation of the data will be necessary.
By undertaking this research, it will be investigated whether or not an increase of magnesium levels in the bone will increase the bone strength of the left and right tibia and femur of a male and female rat.
In order to accurately undertake research regarding the effect of magnesium on bone strength, a three-point bending test on an Instron will be conducted using five rats, three treated with magnesium; two male and one female and two control rats; one female and one male. The treated bones will be dissolved in 300mg Swisse Ultiboost Magnesium” tablet, which is then dissolved 25ml of water per set of two bones (tibia and femur per side). Whereas the control rats will be soaked in demineralised water per set of two bones.
From the three-point bending test, the following biomechanical mechanical indices will be calculated; stiffness, yield load, ultimate load and ultimate deformation. The data collected from this investigation will be collated to then produce a load/deformation curve, which will allow for determination of the intended measures.
The controlled variables of the experiment are the tissue composition; either mineral or organic, as well as the size and the shape of each bone. To account for any differences in the size of the rat bones which might impact the stiffness of the bone, the data is normalised by calculating the diameter of the shaft and the cross-sectional area of the shaft to create a stress/strain curve. From this curve the yield stress, ultimate stress and elastic modules for each rat bone, both control and tested can be determined.
It is hypothesised that with an increase in the amount of magnesium in the rat bones, the ultimate load/stress needed from the 3-point bend test to break the left and right tibia and femur bones of the male and female rat will also increase. This is due to magnesium being essential for absorption and metabolism of calcium which assists in bone strength.

Bone extraction
Grab three lined trays with needed equipment – small and large scissors, scapple. Place one female rat on one tray, and 2 male rat on each of the other trays. Weigh each rat individually and record in workbook. Collect 6 vials and label each with an ID tag as below.