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Men, your sperm know how heavy you are. A new study reveals that sperm carry different chemical tags on their DNA depending on whether their owner is lean or obese. The findings suggest that men may be able to pass information about the availability of food in their environment down to their offspring, which could influence their child's odds of being overweight.

This PowerPoint-driven case study presents three different stories, each of which explores an aspect of membranes. The first (The Exploding Fish) covers diffusion, specifically addressing the question of why animal cells explode in freshwater but fish do not, and differences between saltwater and freshwater fish. The second case (The Pleasurable Poison) is designed to show that alcohol can slip across membranes and also highlights some of the problems of ingesting this toxin. The third case (The Dangerous Diet) explores a weight-loss drug, DNP, and how it operates in mitochondrial membranes. The first of these case studies also includes a number of "clicker" questions. These cases were originally designed for a semester-long, introductory biology course for non-majors, and instructors can choose to use one or all of the cases to suit their course.

The woman in this case had cachexia, a metabolic disorder that affects some 9 million people worldwide, including as many as 80% of people with advanced cancer. It typically involves extreme weight- and muscle-loss, makes routine activities difficult and increases the risk of deadly complications such as infections. Adding calories doesn't reverse cachexia, and McClement says that the disorder sometimes provokes extreme reactions from family members because it serves as visual confirmation of their worst fears. "It's a constant reminder that the person is sick and is not going to get better," says McClement.

Every year during the foodless winter months, bears enter their den and lapse into a state of extended dormancy and slumber (called hibernation). For the next 130+ consecutive days they do not drink, eat, defecate, or urinate. Rarely do they die from starvation, dehydration, or poisoning from waste buildup while hibernating. How do bears prepare for this period of starvation coupled with significant weight loss? Bears are not only the champions of winter rest, but are also the undisputed champions of non-stop summer eating. They are constantly on the move during late spring and all summer long into late autumn oftentimes covering great distances over diverse habitats in their incessant search for locally and seasonally available food. In this case study, students learn the basics about bear denning, hibernation energetics, the differences in size of bear home ranges, and the nutritional landscape they must navigate to prepare for the long months of winter inactivity and caloric deprivation. The case is suitable for a wide audience, including majors or non-majors in lower- or upper-level undergraduate courses in environmental science, ecology, biology, or wildlife science.

Gut microbes-the collection of bacteria and other organisms that inhabit our intestines-have been shown to play a role in a wide variety of conditions from asthma to obesity. But researchers still don't know precisely how they contribute to obesity. To gain a better understanding, a team led by physiologist Mirko Trajkovski from the University of Geneva in Switzerland has been following up on any leads he can to learn about the link between these microbes and metabolism. Trajkovski knew from past research that getting rid of some gut bacteria in mice makes them less able to maintain their internal body temperature in the cold. He wondered whether there might be a connection between gut microbes, external temperature, and weight control.