Proton magnetic resonance spectroscopy of brain in obstructive sleep apnoea in north Indian Asian subjects.

Background & objectives: Repeated apnoeic/hypoapnoeic episodes during sleep may produce cerebral damage in patients with obstructive sleep apnoea (OSA). The aim of this study was to determine the absolute concentration of cerebral metabolites in apnoeic and non-apnoeic subjects from different regions of the brain to monitor the regional variation of cerebral metabolites. Methods: Absolute concentration of cerebral metabolites was determined by using early morning proton magnetic resonance spectroscopy (1H MRS) in 18 apnoeic patients with OSA (apnoeics) having apnoea/hypopnoea index (AHI) >5/h, while 32 were non-apnoeic subjects with AHI< 5/h. Results: The absolute concentration of tNAA [(N-acetylaspartate (NAA)+N-acetylaspartylglutamate (NAAG)] was observed to be statistically significantly lower (P<0.05) in apnoeics in the left temporal and left frontal gray regions compared to non-apnoeics. The Glx (glutamine, Gln + glutamate, Glu) resonance showed higher concentration (but not statistically significant) in the left temporal and left frontal regions of the brain in apnoeics compared to non-apnoeics. The absolute concentration of myo-inositol (mI) was significantly high (P<0.03) in apnoeics in the occipital region compared to non-apnoeics. Interpretation & conclusions: Reduction in the absolute concentration of tNAA in apnoeics is suggestive of neuronal damage, probably caused by repeated apnoeic episodes in these patients. NAA showed negative correlation with AHI in the left frontal region, while Cho and mI were positively correlated in the occipital region and Glx showed positive correlation in the left temporal region of the brain. Overall, our results demonstrate that the variation in metabolites concentrations is not uniform across various regions of the brain studied in patients with OSA. Further studies with a large cohort of patients to substantiate these observations are required.

Proton magnetic resonance spectroscopy of brain to study the cerebral metabolic abnormalities in COPD patients: a case control study in north India.

BACKGROUND: To investigate changes in the cerebral metabolism of nondiabetic and normolipidaemic patients with chronic obstructive pulmonary disease (COPD) using localised in vivo proton magnetic resonance spectroscopy (1H MRS), and to correlate these with the severity of disease. METHODS: Twenty-eight symptomatic COPD patients and 19 healthy controls underwent 1H MRS of brain, pulmonary function testing and respiratory muscle strength evaluation. The parieto-temporal and occipital regions were localised for 1H MRS. The metabolic ratios of N-acetyl aspartate to cretinine (NAA/Cr) and choline containing compound to creatinine (Cho/Cr) were calculated by integrating area under the each peak. RESULTS: The mean value of NAA/Cr and Cho/Cr in parieto-temporal area in COPD patients were (1.86 +/- 0.54) and (0.77 +/- 0.23), respectively. The mean values of NAA/Cr and Cho/Cr in occipital area in COPD patients were (1.75 +/- 0.44) and (0.61 +/- 0.25), respectively. Compared with healthy control subjects, the mean values of Cho/Cr in COPD patients were lower, both in parieto-temporal (0.77 +/- 0.23 vs. 0.89 +/- 0.35; p = 0.17) and occipital (0.61 +/- 0.25 +/- vs. 0.67 +/- 0.08; p = 0.36) areas of the brain. CONCLUSIONS: The cerebral metabolism, pulmonary function testing and respiratory muscle strength altered in symptomatic COPD patients. The clinical significance of cerebral metabolic changes in COPD patients needs to be further investigated.

Assessmrent of iron overload in thalassaemic patients by magnetic resonance imaging: a pilot study.

The patients of thalassaemia major need repeated blood transfusion which leads to excess iron deposition in various organs like liver, heart, pituitary etc. This iron accumulation causes various complications and ultimately organs' failure. There is no non-invasive, standard and reliable method to know the status of iron overload in various organs of the body. This paper attempts to use magnetic resonance imaging to know the liver iron overload in 8 thalassaemic patients as a pilot study. Eight children suffering with thalassaemia and 3 controls who were the normal siblings of the patient group underwent magnetic resonance imaging of the abdomen using spin-echo T, weighted sequence. Blood serum ferritin levels in the patients' group were also determined on the same day of magnetic resonance imaging examination. It was observed that the ratio of magnetic resonance imaging signal intensity (in spin-echo T1 weighted image) in paraspinous muscle to liver was significantly different in normal control (0.65) compared to that in thalassaemia patients (2.1 to 11.4 depending upon extent of iron deposition). The magnetic resonance signal intensity ratio correlated with the blood serum ferritin level of patients (p = 0.01) which is generally taken as indirect measure of body iron burden. Spin-echo sequence is the simplest imaging sequence and it increases the chance of its routine use. The study concludes that magnetic resonance imaging has good potential to quantify the liver iron deposition non-invasively and may denote the efficacy of iron-chelation therapy which is used to reduce the body iron burden in these patients.

Brain areas activated after ejaculation in healthy young human subjects.

Brain mechanisms for the refractory period that characteristically follows ejaculation in animals and human are poorly understood. The possibility of active inhibition of brain areas being responsible for the post-ejaculatory inhibitory state has not been ruled out. Using Blood Oxygen Level Dependent (BOLD) functional magnetic resonance imaging (fMRI) we have mapped brain areas in healthy young volunteers immediately after ejaculation. Functional imaging of the brain for 30 minutes beginning after three minutes of ejaculation induced by masturbation showed spatio-temporal activation in amygdala, temporal lobes and septal areas. The septal areas were observed to be active for a shorter duration than the amygdala and the temporal lobe. Thus the temporal sequence of involvement of the above neural structures may contribute to temporary inhibition of sexual arousal/penile erection during the post-ejaculatory refractory period in humans.

Magnetic resonance imaging: bioeffects and safety concerns.

Magnetic resonance imaging (MRI) is the state-of-the-art noninvasive imaging modality in clinical diagnosis. During MRI examination, the patient is exposed to three different forms of electromagnetic radiation: (i) a static magnetic field, (ii) gradient magnetic fields, and (iii) radiofrequency (RF) fields. Each of these may cause significant adverse bioeffects if applied at sufficiently high exposure levels. This article describes in some detail the areas of health concern for both the patient and the health practitioner with respect to the use of clinical MRI, in addition to describing the potential bioeffects of electromagnetic radiations used in this sophisticated imaging modality.

Structural and conformational study of peptides containing glycine and alanine residues by 13C CPMAS NMR spectroscopy in solid state.

The results of the structural and conformational studies carried out using 13C CPMAS NMR technique on several glycine and alanine containing peptides in the solid state are reported. The study demonstrates the effects of variations in 13C chemical shifts due to conformation and hydrogen bonding. The possibility of applying this technique to obtain insight into the conformational characteristics of peptides of unknown structures is discussed.