By Tiffany Stecker
The case of the hermaphrodite chicken
Scientists at the University of Edinburgh’s Roslin Institute in Scotland have found why some chickens appear to be male on one side of the body, and female on the other.
The research was carried out on birds with white (male) plumage on one side and brown (female) plumage on the other. Previously, experts thought that sex chromosomes in birds controlled the feather colours.
The researchers, however, found that colour may not be linked to chromosomes, but to differences between male and female cells that control the development of sexual traits, called cell autonomous sex identity (CASI).
The findings, published in the journal Nature, may also reveal why males and females exhibit different behaviour and susceptibility to disease.
Knowing the molecular differences between male and female cells could lead to better tests for sexing embryos prior to hatch, playing a part in improving poultry production.
“This research has completely overturned what we previously thought about how sexual characteristics were determined in birds,” said Michael Clinton, one of the researchers for the study. “We now believe that the major factors determining sexual development are built into male and female cells and derive from basic differences in how sex chromosome genes are expressed. Our study opens a new avenue for our understanding of sexual development in birds.”
The group will continue the study to investigate the molecular mechanisms responsible for the differences between male and female cells.1
Schizophrenia-linked memory loss caused by low neurotransmitter levels
A deficiency in a brain chemical may be the reason why schizophrenia patients suffer from cognitive disorders like poor attention, memory loss and difficulties in solving problems. These disorders often accompany the symptoms more often associated with the disease, such as delusions or hallucinations.
The neurotransmitter gamma-aminobutyric acid (GABA) was found to play an important role in regulating cognitive activity in animal models and postmortem analysis of GABA concentrations in human schizophrenic brains. Neuroscientists at the University of California, Davis in the US published their findings on 10 March in the Journal of Neuroscience.
While delusions and hallucinations are usually treated with anti-psychotic drugs to dampen the activity of dopamine, a neurotransmitter linked to psychotic behavior, no medications are available to treat the cognitive impairments of schizophrenia.
“We still know very little about the neurobiology of schizophrenia, particularly at the level of specific circuits and molecules and how their impairments affect behaviour and cognition in the disease,” said Jong H. Yoon, an assistant professor of psychiatry and behavioural sciences at UC Davis and the study’s lead author. “We need this level of specificity to guide targeted treatment development. This is one of the first studies to show that there is a strong association between cognitive deficits and a decrease in a particular neurotransmitter.”
Yoon and his colleagues measured the levels of GABA in the visual cortices of the brains of 13 subjects with schizophrenia and 13 control subjects without the disorder. The schizophrenic patients were found to have a deficit in GABA of about 10 percent, compared to those without the disease.
“The link between changes in patients’ brain chemistry and the cognitive impairments they experience never has been shown before in this way,” said Cameron Carter, professor of psychiatry and behavioral sciences at UC Davis.”This work provides tremendous support for targeting the GABA system for treatment of cognitive decline in schizophrenia.”2
Hearing deprivation can lead to ‘lazy ear’
Short-term hearing deprivation during childhood may lead to persistent hearing deficits, even after hearing is restored to normal, states a study in the March 11 issue of the journal Neuron.
It is known that deprived visual stimulation early in life can cause amblyopia, better known as “lazy eye”. Now researchers have found that the same can be said about amblyaudio, or “lazy ear”.
Like the visual cortex, the auditory cortex must be stimulated early in life to function properly in adulthood. Hearing deprivation can be caused by the buildup of viscous fluid in the middle ear cavity.
In their study, researchers Daniel Polley and Maria Popescu from Vanderbilt University blocked hearing in one ear in infant, juvenile and adult rats and looked at how auditory brain areas were impacted by the temporary hearing loss.
They observed that this disrupted auditory patterning in the brain weakened the deprived ear’s representation and strengthened the open ear’s representation. The effect was also more pronounced when hearing deprivation began in infancy rather than later in life.
“The good news about amblyaudio is that it is unlikely to be a permanent problem for most people,” said Polley. “Even if the acoustic signal isn’t improved within the critical period, the mature auditory cortex still expresses a remarkable degree of plasticity.”
The team will further study whether auditory perceptual training may help accelerate recovery in individuals with processing deficits due to childhood hearing loss.3
New material could replace silicon in electronics
A method for developing a form of carbon called “graphene”- that could rival silicon in its potential for electronics device manufacturing- has been discovered.
The material consists of a layer of graphite 50,000 times thinner than a human hair with properties that could be used in supercomputers, mobile phones and many other electronics.
While it could replace silicone in many cases, expensive and inefficient production methods result in poor-quality graphene that is not practical on an industrial scale.
Head Researcher Victor Aristov, from the Leibniz Institute for Solid State and Materials Research in Dresden, Germany, and his colleagues from various other institutes, said they have developed a simple procedure for making cost-effective graphene.
They team was able to grow high-quality graphene on the surface of silicon carbide wafers, as described in the study published in ACS’ Nano Letters.
“It represents a huge step toward technological application of this material as the synthesis is compatible with industrial mass production,” stated the study.4
- Zhao, D., McBride, D., Nandi, S., McQueen, H., McGrew, M., Hocking, P., Lewis, P., Sang, H., & Clinton, M. (2010). Somatic sex identity is cell autonomous in the chicken Nature, 464 (7286), 237-242 DOI: 10.1038/nature08852 [↩]
- Yoon, J., Maddock, R., Rokem, A., Silver, M., Minzenberg, M., Ragland, J., & Carter, C. (2010). GABA Concentration Is Reduced in Visual Cortex in Schizophrenia and Correlates with Orientation-Specific Surround Suppression Journal of Neuroscience, 30 (10), 3777-3781 DOI: 10.1523/JNEUROSCI.6158-09.2010 [↩]
- Popescu, M., & Polley, D. (2010). Monaural Deprivation Disrupts Development of Binaural Selectivity in Auditory Midbrain and Cortex Neuron, 65 (5), 718-731 DOI: 10.1016/j.neuron.2010.02.019 [↩]
- Aristov, V., Urbanik, G., Kummer, K., Vyalikh, D., Molodtsova, O., Preobrajenski, A., Zakharov, A., Hess, C., Hänke, T., Büchner, B., Vobornik, I., Fujii, J., Panaccione, G., Ossipyan, Y., & Knupfer, M. (2010). Graphene Synthesis on Cubic SiC/Si Wafers. Perspectives for Mass Production of Graphene-Based Electronic Devices Nano Letters, 10 (3), 992-995 DOI: 10.1021/nl904115h [↩]
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