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D K Menon

Publications and source records attributed to D K Menon.

At least 109 records · Page 6Linked to original sources
PubMed1993

A 31P and 1H-NMR investigation in vitro of normal and abnormal human liver.

Spectral changes in human hepatic tumours and possible systemic effects of tumour on host liver were assessed by 31P and 1H in vitro NMR spectroscopy. The 1H and 31P spectra from liver tumour biopsies showed significant elevation in phosphoethanolamine, phosphocholine, taurine, citrate, alanine, lactate and glycine, and significant reduction in GPE (glycerophosphoethanolamine), GPC (glycerophosphocholine), creatine and threonine compared to histologically normal tissue. 31P-NMR spectra obtained from histologically normal tissue within tumour-bearing livers showed significant elevation in phosphoethanolamine and phosphocholine compared to data from liver biopsies from nontumour-bearing patients (pancreatitis). These results suggest that alterations in membrane metabolism in host liver can be detected by 31P-NMR.

Biopsy↗
PubMed1993

A knowledge-based approach to minimize baseline roll in chemical shift imaging.

A method has been developed to minimize baseline roll in chemical shift imaging (CSI). The technique is fully automated and employs knowledge based data processing in the frequency domain. The key feature of the algorithm is the computation of the "trough" and "ripple" components in the CSI data. The baseline roll can be regarded as an artifact that appears as a result of the summation of several sinc functions. Using prior knowledge, a mirror component corresponding to the artifact is created and added to the delayed spectrum. The method compensates for noise and zero-order phase error when computing the roll artifact. The results obtained on implementing the baseline roll minimization procedure on simulated time-delayed spectra indicated that the peak heights and areas were between 91% and 97% in magnitude when compared with the same peaks in the nondelayed spectra. The correction procedure was also assessed on clinical in vivo spectra. Nonlocalized 31P MR spectra of the liver were obtained with and without an acquisition delay of 2.1 ms, and the time delayed spectra subjected to the baseline minimization routine. Metabolite peak heights and areas in the corrected spectra were approximately 94% in magnitude when compared with the same peaks in the original nondelayed whole volume spectra. Implementation of the baseline minimization procedure on in vivo localized spectra with varying signal to noise ratios produced good results. It takes approximately 13 s to implement the baseline roll minimization procedure. In this paper, the technique will be referred to as BaseLine Artifact Suppression Technique (BLAST) routine.

Artifacts↗
PubMed1993

In vivo fluorine-19 magnetic resonance spectroscopy of cerebral halothane in postoperative patients: preliminary results.

This study reports the use of 19F MRS to study halothane in the brain of eight patients recovering from halothane anesthesia of short duration. Resonances attributable to halothane were observed up to 90 min after withdrawal of the anesthetic agent. The signal-to-noise ratio for an unlocalized spectrum acquired using a 6 cm surface coil was typically 20 with data collection times of 2 min. In seven patients a single resonance was seen with a mean (+/- SD) chemical shift of +43.3 (+/- 1.8) ppm, referenced to NaF at 0 ppm. This resonance exhibited a T1 value of between 0.5 and 1 s, and a T2* (estimated from the linewidth of the resonance) between 3.5 and 10 ms. In one patient two resonances were observed with chemical shifts of +38 and +41 ppm. Because we cannot exclude the possibility that this was due to field inhomogeneity, the significance of the last finding is uncertain. However, phantom studies show that the chemical shift of halothane in different environments (such as water, olive oil, methanol, and lecithin) can vary to an extent that accounts for the two resonances seen in our patient. These results demonstrate the feasibility of in vivo 19F MRS studies of fluorinated volatile agents in humans. The potential for clinical 19F MRS of fluorinated anesthetics is discussed.

Adult↗
PubMed1992

Phosphorus-31 magnetic resonance spectroscopy of the human liver using chemical shift imaging techniques.

Phosphorus-31 magnetic resonance spectroscopy of the human liver was undertaken in 28 healthy adult individuals and in 49 patients with liver disease of varying aetiology. Data localised to the liver were obtained using chemical shift imaging techniques. The mean (+/- 1 S.D.) of the peak area ratio phosphomonoesters (PME)/phosphodiesters (PDE) in healthy adult individuals, from spectra obtained with pulse angle 45 degrees and repetition time 1 s, was 0.24 +/- 0.07. The intra-examination variability of this ratio was 20%, the intra-subject variability 27% and the inter-subject variability 32%. An increase in the PME/PDE was observed in the 31P hepatic MR spectrum from primary or secondary tumours in all 17 patients studied, which invariably represented an increase in PME/ATP and, in some cases, a reduction in PDE/ATP. The spectra did not show aetiological characteristics. A non-specific elevation in PME/PDE was also observed in the 31P hepatic MR spectra of 10 (40%) of 25 patients studied who had diffuse liver diseases, such as cirrhosis and infiltrating malignancies. The spectral pattern did not distinguish between diseases of varying aetiologies, but there was a linear correlation between increasing PME/PDE and a reduction in plasma albumin concentrations (p = 0.03). In three patients with hepatic malignancy and abnormal hepatic 31P-MRS, marked spectral changes were observed after successful treatment to debulk the tumour. Only minor changes were observed in the abnormal spectrum of a fourth patient in whom treatment was unsuccessful. Hepatic 31P-MR spectroscopy may prove useful for monitoring disease processes and treatment effects in well characterised patient populations.

Adenocarcinoma↗
PubMed1992

Effect of L-alanine infusion on 31P nuclear magnetic resonance spectra of normal human liver: towards biochemical pathology in vivo.

1. 31P n.m.r. spectroscopy in vivo was used to study the effect of L-alanine infusion on the concentrations of gluconeogenic intermediates in normal human liver. Studies were performed in six healthy male subjects (34-44 years, fasted overnight) using a chemical shift imaging pulse sequence on a whole-body n.m.r. system operating at 1.6T. Hepatic 31P n.m.r. spectra were obtained from 10 min before to 70 min after intravenous administration of 0.70 (n = 2), 1.40 (n = 3) or 2.80 (n = 5) nmol of L-alanine/kg body weight over 4.5 min. Concentrations of phosphomonoesters, Pi and phosphodiesters relative to ATP were calculated from peak areas in the n.m.r. spectra, using the beta-ATP peak as a reference. 2. Dose-dependent spectral changes were observed for [phosphomonoesters]/[ATP] and [Pi]/[ATP]. At the highest dose given, maximal changes in [phosphomonoesters]/[ATP] (mean +/- SEM: 98 +/- 12%, P < 0.005) and [Pi]/[ATP] (-33 +/- 3%, P < 0.001) were observed approximately 45 min after the L-alanine infusion. [Phosphodiesters]/[ATP] showed a maximal increase of 24 +/- 6% (P < 0.05), which was independent of the L-alanine dose. Hepatic ATP levels and pH did not change. 3. To identify the metabolites responsible for the changes observed in vivo, male Wistar rats were infused with 11.2 mmol of L-alanine/kg body weight. After 15 min, livers were freeze-clamped and were extracted according to standard procedures. In vitro, 31P n.m.r. spectra obtained at 8.4 or 11.7 T revealed sharp increases in the concentrations of 3-phosphoglycerate and phosphoenolpyruvate after L-alanine infusion.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine Triphosphate↗
PubMed1992

Magnetic resonance for the anaesthetist. Part I: Physical principles, applications, safety aspects.

Anaesthetists are being increasingly involved in magnetic resonance (MR) procedures, both in patient care and as a research tool. This paper outlines the physical basis of nuclear magnetic resonance and describes its application in magnetic resonance imaging and spectroscopy. Principles of magnet design and safety relevant to anaesthetic practice in a magnetic resonance environment are discussed and guidelines for anaesthetic practice suggested. Some recent clinical magnetic resonance studies of anaesthetic interest are reviewed.

Anesthesiology↗
PubMed1992

Magnetic resonance for the anaesthetist. Part II: Anaesthesia and monitoring in MR units.

Anaesthetists are increasingly involved in patient care during magnetic resonance imaging and spectroscopy. This paper describes a system which has been developed for the management of critically ill patients and the conduct of anaesthesia in a magnetic resonance unit with a 1.6 tesla whole body magnet. Difficulties which arise from working in a confined space in a high magnetic field are highlighted. Different approaches to anaesthesia, sedation and the modification of equipment for use in this environment are reviewed. The problems associated with patient monitoring within a magnetic field are discussed and some solutions are suggested. A transport system for critically ill patients is described and a protocol for management is outlined.

Anesthesia↗
PubMed1991

Coagulation and fibrinolytic activity in Behçet's disease.

Coagulation and fibrinolytic activities were studied in 18 subjects with Behçet's disease and compared with results from 14 matched control patients suffering from sero-negative arthritis. Significantly higher plasma concentrations (median and range) were found in Behçet's patients for the following variables: fibrinogen 3.7 (1.7-6.9) vs 3.0 (2.0-5.1) g/l, p less than 0.05; von Willebrand factor antigen, 115 (72-344) vs 74 (60-119)%, p less than 0.002; plasminogen activator activity (10(6)/ECLT2) 219 (94-329) vs 137 (78-197) units, p less than 0.002; tissue plasminogen activator inhibitor (t-PA-I) activity, 9.1 (5.5-19.3) vs 5.1 (1.8-12.0) IU/ml, p less than 0.002; and PAI-1 antigen, 13.9 (4.5-20.9) vs 6.4 (2.4-11.1) ng/ml, p less than 0.002. Protein C antigen was significiantly lower: 97 (70-183) vs 126 (96-220)%, p less than 0.02. No differences were observed in antithrombin III activity or antigen, factor VIII coagulant activity, fibrinopeptides A and B beta 15-42, plasminogen, alpha-2-antiplasmin, functional and immunological tissue-plasminogen activator, thrombin-antithrombin complexes and D-dimer. Levels of tissue plasminogen activator inhibitor (activity and antigen) correlated with disease activity while fibrinogen and von Willebrand factor concentrations did not. Seven of the 18 subjects with Behçet's disease had suffered thrombotic events but it was not possible to distinguish these from the 11 patients without thrombosis using the assays performed. The results suggest the abnormal fibrinolytic activity in Behçet's disease is due to increased inhibition of tissue plasminogen activator. No abnormality of coagulation or fibrinolytic activity specific to Behçet's disease was detected.

Adult↗
PubMed1990

Relatives' expressed emotion and the course of schizophrenia in Chandigarh. A two-year follow-up of a first-contact sample.

A two-year follow-up was conducted of a subsample of the Chandigarh cohort of first-contact schizophrenic patients from the WHO Determinants of Outcome project. The patients were those living with family members who had been interviewed initially to determine their levels of expressed emotion (EE). The interview was repeated for 74% of the relatives at one-year follow-up. A dramatic reduction had occurred in each of the EE components and in the global index. No rural relative was rated as high EE at follow-up. Of the patients included in the one-year follow-up, 86% were followed for two years. In contrast to the one-year findings, the global EE index at initial interview did not predict relapse of schizophrenia over the subsequent two years. However, there was a significant association between initial hostility and subsequent relapse. The better outcome of this cohort of schizophrenic patients compared with samples from the West is partly attributable to tolerance and acceptance by family members.

Attitude to Health↗
PubMed1987

Expressed emotion and schizophrenia in north India. I. Cross-cultural transfer of ratings of relatives' expressed emotion.

A bilingual rater was trained in English in a technique of assessing relatives emotional attitudes to patients, and was then required to rate material in Hindi without any further experience. This strategy revealed that the rating of critical comments, hostility and positive remarks could be transferred from English to Hindi without distortion. There were problems with the remaining two scales, over-involvement and warmth, but these were due to technical issues connected with rating and not to cross-cultural distortion.

Adolescent↗
PubMed1987

Expressed emotion and schizophrenia in north India. II. Distribution of expressed emotion components among relatives of schizophrenic patients in Aarhus and Chandigarh.

We measured the components of expressed emotion among two samples of relatives of first-contact patients from Aarhus (Denmark) and Chandigarh (India). The Danes were very similar in most respects to samples of British relatives, whereas the Indian relatives expressed significantly fewer critical comments, fewer positive remarks, and less over-involvement. Within the Chandigarh sample, city-dwellers were significantly more expressive than villagers of all EE components except over-involvement.

Adolescent↗
PubMed1987

Expressed emotion and schizophrenia in north India. III. Influence of relatives' expressed emotion on the course of schizophrenia in Chandigarh.

We conducted a one-year follow-up of patients who had made a first contact with psychiatric services in Chandigarh, North India, and had been assigned a diagnosis of schizophrenia. The expressed emotion (EE) of the patients' relatives was assessed early on. We found the same associations between the individual components of EE and relapse of schizophrenia as in previous Anglo-American studies, but only the association between hostility and relapse was statistically significant. Applying the same criteria as in the Anglo-American studies for 'high EE', we found a significant relationship between high EE and relapse rates. We conclude that the significantly better outcome of Chandigarh first-contact patients compared with a London sample is largely due to the significantly lower proportion of high-EE relatives in the North Indian sample.

Attitude to Health↗
PubMedDate not supplied

Effects of fish oil on phospholipid metabolism in human and rat liver studied by 31P NMR spectroscopy in vivo and in vitro.

The effect of omega 3 fatty acids on the metabolism of the normal liver was studied using 31P NMR spectroscopy. Human subjects were examined before and after 1, 3 and 7 days of supplementation with 50 mL fish oil per day (12 g omega 3 fatty acids). 31P NMR spectra (1.6 T) revealed a significant increase in phosphodiester (PDE) to ATP ratios after 1 and 3 days of fish oil. After 7 days, [PDE]/[ATP] ratios at a TR of 1 s had returned to baseline levels, but [PDE]/[ATP] at a TR of 5 s appeared to remain high. Rats were fed diets containing 50% of the energy from fish oil or normal rat chow (controls) for 14 days. 31P NMR liver spectra in vivo (4.7 T) confirmed increased [PDE]/[ATP] in rats fed fish oil compared to controls, although the difference was only statistically significant at a TR of 1.5 s but not at a TR of 8 s. 31P NMR spectra of rat liver extracts (8.7 T) suggested that increased concentrations of glycerophosphocholine and possibly glycerophosphoethanolamine were responsible for rising PDE levels in vivo. Phosphocholine (PC) concentrations were markedly reduced in rat liver after fish oil. The combined rise in glycerophosphocholine and reduction in PC would be consistent with a shift from the phospholipase C to the phospholipase A1/A2 pathway of phosphatidylcholine breakdown after fish oil consumption.

Adult↗