Science Square

  • Issue 85 / January - February 2012

    Fixing obesity in the brain

    The Fountain

    1- Fixing obesity in the brain
    Original article: Czupryn, A. et al., Science 334, 1133 (2011).

    Neurons are a highly specialized group of cells that transmit electrical stimuli to elicit responses in the body. This high specialization comes with a price: with few exceptions, neurons cannot divide to replace nonfunctional ones. Over the past decade, cell therapy, that is treatment of a disease by introducing new cells, has emerged as a new hope for neurological disorders such as spinal cord injury, Alzheimer's disease, and Parkinson's disease, albeit with numerous challenges. One of the major problems in the field is to make the newly-introduced cells integrate into the neural circuitry of the host organism. This proof-of-concept study showed that it is possible for transplanted neurons to functionally integrate into the host brain and cure obesity in a specific genetic mouse model. This genetic mouse model lacks the ability to sense leptin, a hormone that regulates body weight and metabolism. Thus, these mice are prone to obesity and diabetes. The authors transplanted progenitor neurons isolated from the hypothalamus-a part of the brain that regulates numerous functions including metabolism, hunger and body temperature-of normal embryonic mice to the hypothalami of newborn diseased mice. Twenty weeks after the transplantation, cells were shown to be functionally integrated into the native circuitry. Integrated neurons were able to create electrical stimuli, transmit signals and, unlike the native neurons, respond to the hormone, leptin. Amazingly, transplanted mice were 30% lower in body weight and diabetes-free compared to the obese non-transplanted counterparts. The results were dramatic, despite the fact that only a few of the transplanted neurons were actually converted to the neurons that play a role in energy metabolism and leptin response. The authors explain this phenomenon by stating that the transplanted neurons may work as "antennas" to sense leptin and regulate other neurons in the native circuitry. Although current research is far from human application, it is still an important step towards treatment of detrimental neurological diseases.

    2- A new record in solar cell efficiency
    Original Article: Yella, A. et al., Science 334, 629 (2011).

    Since their discovery in 1991, dye-sensitized solar cells (also known as Gr├Ątzel cells) have offered great potential despite their low efficiency values. They consist of dye-soaked titania nanoparticles coupled to an iodide-based electrolyte that allows for absorption of light and its conversion to electricity through the fast transport of electrons. According to a report in Science, researchers from ecole Polytechnique Federale de Lausanne (EPFL) have substantially improved the efficiency values over 12%, making this type of solar cells a feasible contender to the incumbent silicon solar cells. To store the most sunlight, these cells absorb the colors of the light spectrum with the highest energies and reject the rest such as the green light. In addition to the increase in cell efficiency, Gr├Ątzel and coworkers have also reduced their cost by replacing expensive ruthenium dyes with a zinc-based dye. Finally, they have improved the voltage output by using a cobalt electrolyte, a redox system that is more compatible than the previous iodide systems. This new system with improved components has also increased the theoretical maximum efficiency to 30%, which will require further optimization in device design and engineering to achieve. The only major drawback is the use of organic solvents potentially limiting the efforts for large-scale fabrication.

    3- IQ can still change in teenage years
    Original Article: Ramsden S. et al., Nature 479, 113 (2011).

    Intelligence quotient (IQ) is a standardized measure of human intellectual capacity that takes into account a wide range of cognitive skills. IQ is generally considered to be stable across the lifespan, with scores at one time point being used to predict educational achievement and employment prospects in later years. However Prof. Cathy Price and colleagues have found that verbal and non-verbal IQ can rise or fall in the teenage years. They tested 33 teenagers-19 boys and 14 girls-in 2004, when they were 12 to 16 years old, and again in 2008, when they were 16 to 20 years old. Each time, the teens took IQ tests that measured their verbal and nonverbal abilities. Then, using magnetic resonance imaging, the researchers scanned the teenagers' brains while they performed verbal tasks, such as reading or naming objects, and nonverbal tasks, such as solving visual puzzles with their hands. The idea was to match their test scores with a picture of their brain structure and activity at each time. The test results revealed dramatic changes between their first testing and their second: verbal and nonverbal IQ scores of participants rose or fell by as many as 20 points (on a scale with an average score of 100). Some teens improved or declined in either their verbal or nonverbal skills, while others improved in one area and declined in the other. The brain scans mirrored the score differences. For example, in teens whose verbal IQ scores had increased, the scans showed increased gray matter density in a region of the brain activated by speech. Teens whose nonverbal skills had improved showed changes in a brain region associated with motor movements of the hand. The authors note that these were the largest changes observed, and that there might be many more that were not noticed.

    4- A coordination path from an infant's heart to the mother's heart
    Original Article: Feldman, R. et al., Infant Behavior and Development 34, 569 (2011).

    A group of researchers sat 40 pairs of mothers and 3-month-old infants face-to-face, equipped with sticky skin electrodes on either side of their hearts. Beat for beat, mother and child's hearts thumped together almost instantly as they shared loving looks or contented coos. This cardiac coupling worked only for moms with their own babies, and only when the duos synchronized smiles and other cheerful social behaviors. The researchers suspect that when humans mirror each other's facial expressions, they may switch on specific areas in the brain that tell the heart when to thump. Melding with mom lasts longer than just a few beats, however. Babies who don't tune in with their mothers are less empathetic as teenagers, according to previous work from the same group. Premature infants or those whose mothers have postpartum depression may be most at risk for losing this social skill because they miss out on early opportunities to interact with their mothers. The authors state that future research is required to examine the impact of interaction synchrony on other physiological processes, such as hormonal release or brain activation.


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