Early Differential Neurometabolite Response of Hippocampus on Exposure to Graded dose of Whole Body Radiation: An in Vivo 1H MR Spectroscopy Study

Whole body radiation exposure induced injury may occur during medical or industrial accidents as well as during terrorist radiation exposure scenario. A lot of information is available on alterations in brain function and metabolism post localised cranial irradiation; changes in brain associated with whole body radiation exposure are still limited. The present study has been conducted to assess early differential effect of low and high whole body radiation exposure on hippocampus neurometabolites using in vivo proton magnetic resonance spectroscopy (1H MRS). Hippocampal 1H MRS was carried out in controls (n = 6) and irradiated mice exposed to 3 Gy, 5 Gy, and 8 Gy of radiation (n = 6 in each group) at different time points i.e., day 0, 1, 3, 5 and 10 post irradiation at 7 T MRI system. Quantitative assessment of the neurometabolites was done using LCModel. The results revealed significant decrease in myoionisitol (mI)/creatine (tCr) and taurine (tau)/tCr in animals exposed to 5 Gy and 8 Gy dose compared to controls. In 3 Gy dose group, none of the metabolites showed significant alterations at any of the time point post irradiation as compared to controls. Overall our findings suggest differential change in hippocampal volume regulatory mechanism associated neuro-metabolites following whole body radiation exposure with maximum reduction in case of high dose group. We speculate that these alterations may be a consequence of oxidative stress, neuro inflammation or systemic inflammatory response following whole body radiation exposure

Cortical activity modulation of language processing by dynamic optimization of task complexity and functional restrictions

Language, regarded as a hierarchical cognitive code activated by functional operational modes of the brain by most neuropsychologists, is characterized by increased cognitive load in successively higher levels of processing. Language comprehension is posited to be executed through symbolic-iconic information being encoded neurally as modulated phenomena, and can be studied _in vivo_ by functional brain imaging. Using a lexical decision-making task in conjunction with syntactic error correction that effectively isolated the regulatory neural substrate of processing structural-functional information, and minimizing the possible confounds of gender and proficiency, functional magnetic resonance imaging (fMRI) was performed on bilingual volunteers to ascertain the attentional modulation of second language lexical and sentence processing. Our results indicate that while a right posterior cingulate gyrus-precuneus-lingual gyrus-cerebellar loop processes lexical information, the left inferior and middle frontal cortices are critically involved in the implementation of a structural-functional decision-making procedural loop in mediating second language comprehension

Non-invasive assessment of oxidative capacity in young Indian men and women: A ³¹P magnetic resonance spectroscopy study

263-268It is generally assumed that men display greater strength and muscle capacity than women. However, previous biochemical and histological studies have shown that men have greater capacity for anaerobic metabolism and women have higher or similar oxidative metabolism. Therefore, in the present study, we estimated oxidative capacity of gastrocnemius muscle and compared in Indian men and women using non-invasive in vivo ³¹P magnetic resonance spectroscopy (MRS). Healthy subjects (8 young males and 9 females, age-matched) performed plantar flexion exercise within a magnet and MRS measurements of inorganic phosphate (Pi), phosphocreatine (PCr), ADP, and pH of the calf muscles were carried out using a 1.5 T whole-body MRI system. PCr values during recovery were fitted to an exponential curve, and oxidative capacity was calculated using rate constant (kPCr), as an index of oxidative phosphorylation. When men and women were compared for different metabolic ratios, ADP, pH, kPCr and oxidative capacity, all parameters turned out to be statistically insignificant. The results showed no gender effect on skeletal muscle oxidative metabolism. The study demonstrated the usefulness of such non-invasive method to indirectly measure the oxidative capacity of the muscle based on PCr recover