Life Lines by Dr. Dolittle

Tag Archive for ‘American Journal of Physiology’

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Study examines how statin exposure affects cholesterol metabolism in fish

Despite its bad reputation, cholesterol serves many important functions in the body. It is necessary for normal cell structure and is a precursor for the formation of steroid hormones, vitamin D, and bile acids. Too much “bad” cholesterol (LDL), however, can promote cardiovascular diseases and nonalcoholic fatty liver disease. For this reason, many animals tightly regulate cholesterol levels in the body. Fish often have higher cholesterol levels than humans and […]

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Is it just a fluke?

Lung flukes, Hematoloechus sp., are pesky little parasites. Up to 89 species of lung flukes have been identified to date. Their life cycle includes two intermediate hosts, the first of which are freshwater snails that swallow fluke eggs. After ingestion, the eggs hatch and produce a larval form of the parasite called cercaria, which are shed from the snails and taken up by damselflies or dragonflies. These are quite the […]

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New paper explores how our complex kidneys evolved

The kidneys are remarkable organs responsible for filtering blood and creating urine. To learn more about how they do this, check out this YouTube video: The evolution of glomerular filtration is what allows animals to regulate the disposal of ions such as calcium, magnesium, sodium, potassium, and sulfate. Some solutes are reabsorbed from the urine and returned to the body with the help of sodium ions, whereas other solutes are […]

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The physiology of ‘frogsicles’ and the quest for life after death

Cope’s gray treefrogs, Dryophytes chrysoscelis, are remarkable animals that can actually survive being frozen…multiple times each year. In fact, these animals live in an environment in which temperatures commonly dip below freezing. When temperatures drop, up to 65% of their body water literally freezes. In anticipation of freezing temperatures, they begin to accumulate cryoprotectant chemicals during the fall to help protect their organs. Until now, the effects of repeated cycles […]

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Sodium is necessary to absorb some dietary nutrients

As frogs develop, their intestines become shorter and the cells on the inner lining of the intestine change. Researchers have suspected that these changes help the animals transition from a diet consisting of mainly algae as a tadpole to a carnivorous diet in adulthood. This was the subject of a recent study published in the American Journal of Physiology – Regulatory, Integrative and Comparative Physiology, which examined how the intestine […]

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Targeting smells to fight obesity

Admittedly, this is not necessarily a comparative physiology topic. But I couldn’t help exploring this idea as I am munching on a chocolate chip cookie that smelled just too appetizing to walk by. Some restaurants have been accused of intentionally “pumping” out enticing smells to attract customers. After all, the aromas of cooking and baking can attract hungry customers, as well as those who had no intention of seeking out […]

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Researchers discover a way to improve glucose regulation in fish

Many species of carnivorous fish have a difficult time metabolizing carbohydrates, resulting in hyperglycemia. In these affected species, lipids and glycogen (the storage form of glucose) build up in tissues and their growth is slowed when they are fed carbohydrate-rich diets. In addition, these fish continue to produce glucose (through gluconeogenesis) even if they consume it in their diets, which worsens their hyperglycemia. This is a major concern in the […]

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Migratory birds create their own water to prevent dehydration

Migratory birds are amazingly adapted for long-distance flights and can switch the fuels they rely on to support their endurance activities. Unlike humans that burn mainly carbohydrates for endurance exercise, avian flight is fueled mainly by fats and some proteins. In a recent study published in the American Journal of Physiology – Regulatory, Integrative and Comparative Physiology researchers examined how white-throated sparrows (Zonotrichia albicollis) prepared for migration. By altering the […]

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One reason why fish and mammals lose their appetite during stress

I don’t know about you, but sometimes I lose my appetite when I am really stressed. The endocrine system is responsible for controlling our stress responses and involves three main endocrine glands – the hypothalamus, pituitary, and adrenal gland. Hence, the stress pathway is often referred to as the “HPA axis”. When we are stressed, the hypothalamus releases a hormone called corticotropin releasing factor (CRF), which triggers the release of […]

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Heat may activate muscle growth and prevent atrophy

Skeletal muscle is not only important for our ability to move, it also plays a major role in metabolism. Under normal conditions, the routine processes of muscle growth (hypertrophy) and breakdown (atrophy) are in balance. While many of us are aware that exercise and healthy diets promote muscle growth, diseases and sedentary lifestyles can promote muscle atrophy. Studies examining the effects of heat on muscle – from environmental heat, direct […]

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