Differences in prefrontal cortex GABA/glutamate ratio after acute restraint stress in rats are associated with specific behavioral and neurobiological patterns.

In patients suffering from stress-related pathologies and depression, frontal cortex GABA and glutamate contents are reported to decrease and increase, respectively. This suggests that the GABA and/or glutamate content may participate in pathological phenotype expression. Whether differences in frontal cortex GABA and glutamate contents would be associated with specific behavioral and neurobiological patterns remains unclear, especially in the event of exposure to moderate stress. We hypothesized that an increase in prefrontal cortex GABA/glutamate ratio would be associated with a blunted prefrontal cortex activation, an enhanced hypothalamo-pituitary-adrenocortical (HPA) axis activation and changes in behavior. Rats being restrained for 1-h were then tested in an open-field test in order to assess their behavior while under stress, and were sacrificed immediately afterward. The GABA/glutamate ratio was assessed by (1)H high-resolution magic angle spinning magnetic resonance spectroscopy ((1)H-HRMAS-MRS). The neurobiological response was evaluated through prefrontal cortex mRNA expression and plasma corticosterone levels. The stressed rats were distributed into two subgroups according to their high (H-G/g) or low (L-G/g) GABA/glutamate ratio. Compared to the L-G/g rats, the H-G/g rats exhibited a decrease in c-fos, Arc, Npas4, Nr4a2 mRNA expression suggesting blunted prefrontal cortex activation. They also showed a more pronounced stress with an enhanced rise in corticosterone, alanine aminotransferase (ALAT), aspartate aminotransferase (ASAT), creatine kinase (CK) and lactate dehydrogenase (LDH) levels, as well as behavioral disturbances with decreased locomotion speed. These changes were independent from prefrontal cortex energetic status as mammalian target of rapamycin (mTOR) and adenosine monophosphate-activated protein kinase (AMPK) pathway activities were similar in both subpopulations. The differences in GABA/glutamate ratio in the frontal cortex observed in the stressed animals may participate in shaping individual differences in psychophysiological reactions.

What you always wanted to know about the history and physical examination of neck pain but were afraid to ask.

Diagnoses of most cases of neck pain can be made on the basis of a careful history and physical examination. Any tests must be interpreted only in the context of the clinical examination. The clinician must be cognizant of signs or symptoms that may indicate a more serious disorder by attending to the red flags and examining the lower extremities for spasticity that could indicate cervical myelopathy.

[Geo-demography of Turkey: a difficult transition]. / Geo-demographie de la Turquie: une transition difficile

PIP: Recent demographic trends in Turkey are examined. The author notes that a demographic transition involving declines in fertility and mortality is in full swing, although its level and speed vary significantly among regions. Consideration is given to spatial distribution, internal migration patterns, and urbanization. With regard to international migration, the author observes a decline in the importance of labor migration to Europe and a growth in labor migration to Arab countries. (summary in ENG)^ieng

Evidence for mantle metasomatism by hydrous silicic melts derived from subducted oceanic crust.

The low concentrations of niobium, tantalum and titanium observed in island-arc basalts are thought to result from modification of the sub-arc mantle by a metasomatic agent, deficient in these elements, that originates from within the subducted oceanic crust. Whether this agent is an hydrous fluid or a silica-rich melt has been discussed using mainly a trace-element approach and related to variable thermal regimes of subduction zones. Melting of basalt in the absence of fluid both requires high temperatures and yields melt compositions unlike those found in most modern or Mesozoic island arcs. Thus, metasomatism by fluids has been thought to be the most common situation. Here, however, we show that the melting of basalt under both H2O-added and low-temperature conditions can yield extremely alkali-rich silicic liquids, the alkali content of which increases with pressure. These liquids are deficient in titanium and in the elements niobium and tantalum and are virtually identical to glasses preserved in mantle xenoliths found in subduction zones and to veins found in exhumed metamorphic terranes of fossil convergent zones. We also found that the interaction between such liquids and mantle olivine produces modal mineralogies that are identical to those observed in metasomatized Alpine-type peridotites. We therefore suggest that mantle metasomatism by slab-derived melt is a more common process than previously thought.