Risk prediction-Homocysteine in Coronary Heart Disease.

Majority of patients who experience a Coronary Heart disease event have one or more of the conventional risk factors for atherosclerosis and so do many people who have not yet experienced such an event. Thus predictive models based on conventional risk factors have lower than the desired accuracy, providing a stimulus to search for new factors to predict accurately the risk of CHD. In this regard newer risk factors like homocysteine, Lp(a), insulin resistances are the important ones and are called as 'novel risk factors'. The study was undertaken to find the prediction of CHD risk by homocysteine in comparison with other conventional risk factors. The data obtained suggests a very high sensitivity, specificity and accuracy with above 90% positive prediction value for homocysteine in CHD patients when compared to commonest conventional risk factors.

Analysis of glutathione in rat airway surface liquid by capillary zone electrophoresis with conductivity detection.

Glutathione (GSH) is an important component of antioxidant defenses in airway surface liquid (ASL), a thin layer (10-30 microm) of liquid covering the epithelial cells lining the airways of the lung. Decreased levels of ASL GSH have been reported in cystic fibrosis (CF), potentially contributing to the severe oxidative stress seen in this disease. To help investigate the role of GSH in ASL, we developed a technique suitable for analysis of GSH and its oxidized form (GSSG) in microliter samples using capillary sampling followed by capillary zone electrophoresis (CZE) analysis with conductivity detection. CZE was carried out in 100 mM CHES and 40 mM lithium hydroxide with 5 mM spermine at pH 9.1 under an applied electric field of -416 V cm(-1). To prevent any autooxidation of GSH during sample manipulations, the samples were treated with N-ethylmaleimide (50 mM) to alkylate free thiol (-SH). Under these conditions, GSH and GSSG were cleanly separated without interference from common anions (e.g. Cl(-), PO(4)(3-), HCO(3)(-), etc.) and the limit of detection for ASL analysis was 11 microM for GSH and 8 microM for GSSG (S/N=3). GSH and GSSG were also measured in rat plasma. Baseline values of 897+/-210 microM (GSH) and 215+/-61 microM (GSSG) were obtained for rat ASL (n=8), whereas 12.4+/-2.7 microM (GSH) and 14.8+/-6.7 microM (GSSG) were obtained for rat plasma (n=5).

Hyperhomocysteinemia: An emerging risk factor for cardiovascular disease.

There is considerable epidemiological evidence, which confirms the importance of plasma homocysteine as a powerful predictor of future risk of coronary heart disease and other complications of atherosclerosis. Treatment of hyperhomocysteinemia varies with the underlying cause. However, an inexpensive vitamin supplementation with folic acid, vitamin B12 and vitamin B 6 is generally effective in reducing homocysteine concentrations. Several randomised, controlled trials evaluating the effects of folic acid based supplements on homocysteine concentrations have been conducted over the last decade. In most patients, folic acid alone, and in combination of vitamin B12 and B6, has been shown to reduce homocysteine concentrations within four to six weeks after the initiation of therapy (34).However, no study has yet demonstrated that lowering of homocysteine by vitamin supplementation decreases the cardiovascular morbidity or mortality. Avoidance of excessive meat intake and increased consumption of fresh vegetables and fruits is a dietary measure, which has many health benefits, including a potential to reduce elevated homocysteine levels. The other reasonable approach is to determine levels of fasting homocysteine in high risk patients and it may be advisable to increase their intake of vitamin fortified foods and/or to suggest the daily use of supplemental vitamins. Several large scale randomised trials like Heart Outcomes Prevention Evaluation (HOPE-2) Study, Mcmaster University, Canada, Study of the Effectiveness of Additional Reductions in Cholesterol and Homocysteine (SERCH), Clinical Trial Service Unit, Oxford, U.K, Cambridge Heart Antioxidant Study (CHAOS-2) University of Cambridge, U.K, Bergen Vitamin Study, University of Bergen Norway, Women's Antioxidant and Cardiovascular Disease Study (WACS) Harvard Medical School, U.S.A, Prevention with a combined inhibitor and folate in Coronary Heart Disease (PACIFIC) study, University of Sydney, Australia, and many others are ongoing to assess the effect of homocysteine-lowering by vitamin supplementation on risk of vascular disease.

Lipoprotein (a) in coronary artery disease in Indian population.

Prevalence of coronary artery disease (CAD) in Indian population is gradually increasing at an alarming rate. Traditional risk factors fail to explain the high incidence of CAD. Although lipoprotein(a) has been shown to be a risk factor for atherosclerosis, there is very limited data regarding Indian patients. The present study was therefore undertaken to assess the role of lipoprotein(a) levels as a risk factor in CAD in Indian patients. Clinical profile, lipid profile, coronary angiography and lipoprotein(a) levels were assessed in 300 patients with CAD and 200 controls with no CAD. There was no significant difference in age, conventional risk factors like diabetes, hypertension, smoking, family history and lipid parameters between the two groups. The mean plasma lipoprotein(a) levels in patients with CAD was 32.18 +/- 1.37 mg/dl. The value was not significantly higher than that of the mean of 29.94 +/- 2.59 mg/dl of lipoprotein(a) in the control group. In the subgroup of diabetics and patients with myocardial infarction there was a trend towards increased lipoprotein(a) levels compared to controls but the difference was not statistically significant. Nor there was any relationship between lipoprotein(a) levels and number of stenosed coronary arteries. Thus the study shows that lipoprotein(a) levels do not significantly correlate with the presence of coronary artery disease.

Serum markers for early diagnosis of non-'Q' wave and 'Q' wave myocardial infarction.

The present study conducted on twenty-five uncomplicated cases of acute myocardial infarction diagnosed by clinical and electrocardiographic findings indicated significantly increased level of cardiac Troponin-T and increased activities of the enzymes total creatine kinase, creatine kinase-MB, aspartate transaminase and lactate dehydrogenase as compared to the twenty-five healthy control subjects. The level of cardiac Troponin-T and the activities of the enzymes total creatine kinase, creatine kinase-MB, aspartate transaminase and lactate dehydrogenase was found to be higher in "Q" wave myocardial infarction patients as compared to the non-"Q" wave and the controls. Since cardiac Troponin-T has been shown to increase in unstable angina and renal failure without cardiac disease and creatine kinase-MB activity has been found to be normal in patients with unstable angina and increase very slightly in patients with renal failure, it was concluded that a combination of cardiac Troponin-T and creatine kinase-MB activity was sufficient for the early diagnosis of acute myocardial infarction.

Proton NMR chemical shifts and coupling constants for brain metabolites.

Proton NMR chemical shift and J-coupling values are presented for 35 metabolites that can be detected by in vivo or in vitro NMR studies of mammalian brain. Measurements were obtained using high-field NMR spectra of metabolites in solution, under conditions typical for normal physiological temperature and pH. This information is presented with an accuracy that is suitable for computer simulation of metabolite spectra to be used as basis functions of a parametric spectral analysis procedure. This procedure is verified by the analysis of a rat brain extract spectrum, using the measured spectral parameters. In addition, the metabolite structures and example spectra are presented, and clinical applications and MR spectroscopic measurements of these metabolites are reviewed.

Spectral simulations incorporating gradient coherence selection.

Computer-aided methods can considerably simplify the use of the product operator formalism for theoretical analysis of NMR phenomena, which otherwise becomes unwieldy for anything but simple spin systems and pulse sequences. In this report, two previously available programming approaches using symbolic algebra (J. Shriver, Concepts Magn. Reson. 4, 1-33, 1992) and numerical simulation using object-oriented programming (S. A. Smith, T. O. Levante, B. H. Meier, and R. R. Ernst, J. Magn. Reson. A 106, 75-105, 1994) have been extended to include the use of gradient operators for simulation of spatially localized NMR spectroscopy and gradient coherence selection. These methods are demonstrated using an analysis of the response of an AX(3) spin system to the STEAM pulse sequence and verified with experimental measurements on lactate.

Automated spectral analysis I: formation of a priori information by spectral simulation.

A spectral simulation method is described for generating a priori information for use in parametric spectral analysis. The method makes use of GAMMA (S. A. Smith, T. O. Levante, B. H. Meier, R. R. Ernst, J. Magn. Reson., 106A, 75-105, 1994), a programming environment that facilitates simulation of magnetic resonance phenomena. The input parameters consist of the chemical shifts and scalar spin-coupling constants for the compounds to be analyzed, the acquisition pulse sequence, and the field strength used. The resultant spectral information consists of the relative amplitude, frequency, and phase of all resonances, which are stored in a spectral database. This procedure can be rapidly and conveniently modified to reflect different acquisition parameters and data analysis requirements.

Automated spectral analysis III: application to in vivo proton MR spectroscopy and spectroscopic imaging.

An automated method for analysis of in vivo proton magnetic resonance (MR) spectra and reconstruction of metabolite distributions from MR spectroscopic imaging (MRSI) data is described. A parametric spectral model using acquisition specific, a priori information is combined with a wavelet-based, nonparametric characterization of baseline signals. For image reconstruction, the initial fit estimates were additionally modified according to a priori spatial constraints. The automated fitting procedure was applied to four different examples of MRS data obtained at 1.5 T and 4.1 T. For analysis of major metabolites at medium TE values, the method was shown to perform reliably even in the presence of large baseline signals and relatively poor signal-to-noise ratios typical of in vivo proton MRSI. Identification of additional metabolites was also demonstrated for short TE data. Automated formation of metabolite images will greatly facilitate and expand the clinical applications of MR spectroscopic imaging.

Measurement of chemical shifts and coupling constants for glutamate and glutamine.

Proton chemical shifts and coupling constants were obtained for glutamate and glutamine in water (D2O) at pH = 6.6. Initial chemical shift and coupling constant values obtained from experimental spectra were refined using a spectral simulation and optimization program to get a complete set of values that could not otherwise be measured directly from the experimental spectra due to strong spin-spin couplings. These values are essential for automated spectral fitting procedures that require a priori information.

Multiple-echo proton spectroscopic imaging using time domain parametric spectral analysis.

A multiple-echo MR spectroscopic imaging (MRSI) method is presented that enables improved metabolite imaging in the presence of local field inhomogeneities and measurement of transverse relaxation parameters. Short echo spacing is used to maximize signal energy from inhomogeneously line-broadened resonances, and time domain parametric spectral analysis of the entire echo train is used to obtain sufficient spectral resolution from the shortened sampling periods. Optimal sequence parameters for 1H MRSI are determined by computer simulation, and performance is compared with conventional single-echo acquisition using phantom studies at a field strength of 4.7 T. A preliminary example for use at 1.5 T is also presented using phantom and human brain MRSI studies. This technique is shown to offer improved performance relative to single-echo MRSI for imaging of metabolites with shortened T2* values due to the presence of local field inhomogeneities. Additional advantages are the intrinsic measurement of metabolite T2 values and determination of metabolite integrals without T2 weighting, thereby facilitating quantitative metabolite imaging.

Changes in magnetic resonance imaging and sex behavior after 6-OHDA injection in the medial preoptic area.

Magnetic resonance imaging (MRI) of the brains of male rats was done before and after destroying the catecholamine (CA) fibers by local application of 6-hydroxydopamine (6-OHDA) in the medial preoptic area (mPOA). The male sexual behavior was also assessed before and after injection of this toxic drug. The administration of 6-OHDA (8 microg) resulted in highly variable lesions, as shown by MRI and confirmed by histological examination. A hyperintense area was visible either on one or on both sides, about 1-3 h after the administration of the drug. Postmortem histofluorescence showed destruction of CA fibers in the mPOA on those sides that showed hyperintense areas in the MRI. No CA fiber destruction was seen in those rats that had shown no change in MRI after 6-OHDA injection. There was a transient reduction in sex drive score in all the 6-OHDA-treated rats. The present findings point out a correlation between the MRI changes and CA fiber destruction, whereas the transient reduction in the sexual behavior was not related to these changes. It is suggested that some biochemical events related to 6-OHDA destruction of CA fibers may have been responsible for the hyperintensity seen in the MRI.

Volume localized in vivo proton MR spectroscopy of breast carcinoma: variation of water-fat ratio in patients receiving chemotherapy.

Results are reported on in vivo volume localized proton magnetic resonance spectroscopy (MRS) of patients (n = 44) suffering from carcinoma of the breast, using a bilateral breast surface coil. Localized proton MR spectra of the unaffected contralateral breast of these patients are dominated by resonances arising from fat and are similar to the breast tissue from normal volunteers (controls, n = 13), while in the malignant breast tissues the water resonance dominates. On the other hand, the water suppressed proton MR spectra of malignant breast tissue reveal several metabolites of low concentration including the choline peak around 3.2 ppm and other resonances attributable to purine and pyrimidine nucleotides, in the 8.5 ppm region. Elevated water- fat (W-F) ratios are measured in the malignant tissues, compared with the normal breast tissue of controls and from the contralateral unaffected breast tissue of the patients (n = 11). In the case of patients receiving chemotherapy resulting in the reduction of primary tumor size, the W-F ratio shows a statistically significant (P < 0.01) decrease compared with the pre-therapy value, thus providing a non-invasive indicator of favourable clinical outcome of neoadjuvant chemotherapy for locally advanced breast cancer. The method provides the potential for non-invasively monitoring and assessing the response of breast cancer to neoadjuvant chemotherapy.

1H magnetic resonance imaging and 31P magnetic resonance spectroscopy in experimental filariasis.

1H Magnetic resonance imaging and 31P magnetic resonance spectroscopy (MRS) have been carried out in experimental rodent filariasis, i.e., Acanthocheilonema viteae infection in the rodent host, Mastomys coucha. The T2-weighted image of the infected host shows fine hyperintense thread like structures of adult filariid nests in the cervical region. 31P MRS of normal and infected hosts, localized over the same region of interest, show seven major peaks corresponding to phosphomonoesters (including glucose-6-phosphate, fructose-6-phosphate, fructose-1-6-diphosphate, phosphorylcholine, and adenine monophosphate or AMP), inorganic phosphate, glycerophosphorylcholine, phosphoenolpyruvate, phosphocreatine and nucleoside di- and tri-phosphates. Concentrations of phosphomonoesters (PMEs) are higher in the normal rodent compared with the infected ones. In vivo 31P MRS provides a non-invasive assessment of tissue bioenergetics and phospholipid metabolism.

Effects of brain membranes on 1H nuclear magnetic resonance signal intensity of ethanol in vitro.

In vivo proton nuclear magnetic resonance (1H NMR) studies of ethanol in animal and human brains have shown that only a fraction of ethanol in brain is visible by NMR. The goals of these in vitro 1H NMR experiments were to determine: (1) whether the interaction of ethanol with brain membranes in vitro diminishes ethanol visibility; and (2) if a magnetization transfer (MT) effect can be observed for the interaction of ethanol with brain membranes in vitro. Furthermore, pilot studies were performed to determine if the brain membranes from rats chronically exposed to ethanol had a different effect on ethanol NMR visibility and spin-spin relaxation time (T2) than brain membranes obtained from control rats. Results show that the NMR visibility of ethanol is lower in rat brain membrane suspensions in vitro as compared to ethanol in saline solutions. The factors decreasing ethanol NMR visibility are T2 relaxation, water presaturation time, and off-resonance saturation by a frequency-dependent MT pulse. One-pulse NMR measurements without water presaturation showed that ethanol visibility was significantly increased by 15% in brain membrane suspensions of ethanol-fed rats, suggestive of decreased ethanol partitioning compared to controls. Furthermore ethanol in brain membrane suspensions from ethanol-fed rats showed smaller MT effects than from control rats. These results provide a mechanism for decreased NMR visibility of ethanol in brain, and suggest that chronic exposure to ethanol produces membrane changes which result in increased NMR visibility.

Magnetic resonance imaging of NMDA-induced lesion of the medial preoptic area and changes in sleep, temperature and sex behaviour.

Destruction of the medial preoptic area (mPOA) neurons of rat brain, induced by intracerebral injection of N-methyl D-aspartic acid (NMDA), has been studied by employing the non-invasive Magnetic Resonance Imaging (MRI) technique. Changes in the MRI images are compared and correlated with the functional changes after the mPOA lesion. The progress of the lesion at the injected site has been monitored (using MRI) from 15 min to 1 month after the stereotaxic microinfusion of NMDA (5 micrograms in 0.2 microliter). This study shows that the localised hyperintense (bright) area starts appearing at the mPOA from 3 h after NMDA injection, and the brightness increases progressively for about 2 days. The size and brightness of hyperintense area decrease thereafter. It has not been possible to locate the lesion site after 3 days, using MRI, except in one rat where a vacuole-like area was seen at the NMDA injected site on postmortem histological examination. The reduction in sleep after the mPOA lesion does not show any correlation with the changes in MRI, as it persists throughout the 3 weeks of recording. On the other hand, the initial drastic reduction in male sex behaviour and the increase in body temperature correlated to some extent with the increased brightness in MRI at the site of lesion. The size and location of the hyperintense area, observed during the first 2 days, match with the lesioned area which was histologically identified after 1 month of NMDA administration. Control administration of normal saline into the mPOA did not produce any alteration in the brightness of the MRI image and practically no loss of neurons at the injected site. Though some functional changes have correlation with the alteration in MRI, this cannot be used to interpret the changes in all the physiological parameters. This study also demonstrates that the disappearance of the brightness in MRI should not be taken to indicate a positive prognosis. Though the lesion could not be seen in MRI within 2 hours, its detection after 3-4 h (but within 3 days) after NMDA lesion would give very valuable information for long term studies.

Magnetic resonance imaging of temporal changes of neurotoxic lesion in the rat.

Destruction of striatal neurons in the rat brain, induced by intracerebral injection of N-methyl D-aspartic acid (NMDA), has been visualized noninvasively by magnetic resonance imaging (MRI). The changes in images were monitored from 12 h to one month after the stereotaxic microinfusion of NMDA (10 micrograms in 0.4 microliter) into the striatum, using a T2-weighted rapid acquisition by relaxation enhancement (RARE) sequence. A localised hyperintense (bright) area was visible after 12 h at the site of the injection, and it persisted for the next three days. The size of the hyperintense area decreased thereafter and, after one week, the increased brightness was restricted to the lateral ventricle. Post-mortem histological examination, done after one month, showed a dilated lateral ventricle. The size and location of the lesioned area, identified in histological sections, corresponded to the hyperintense area observed during these initial days after NMDA lesion. The present study demonstrates that noninvasive MRI techniques, using a typical RARE sequence, offer a powerful tool for the early detection of neurotoxic lesion of the brain area, although some caution is required in its use for estimating the size of the lesioned area three days after its formation. The present findings indicate that, in long-term studies, alterations of the neighbouring structures, such as enlargement of the ventricular system, may confound the MRI evaluation of neurotoxic lesions in vivo.

In vivo magnetic resonance study of the histochemistry of coconut (Cocos nucifera).

Magnetic resonance imaging (MRI) and localized proton MR spectroscopy (MRS) techniques have been applied for studying different maturation processes in the histochemistry of coconut (Cocos nucifera). Images of the tender and mature coconut are characterized by protons of the aqueous solution present in the cavity and from the surrounding pulp, whereas the image of the dry coconut is from the protons of the fat present in the pulp. Localized proton MR spectra of the water present in the cavity from the tender and the mature coconut show several resonances due to different chemical constituents of coconut water, whereas typical spectra of the pulp from dry coconut reveal a profile of the hydrogens present in the saturated and unsaturated fatty acid chains. In addition, images obtained from a rancid coconut show the extent of internal damage and degradation due to fungal growth; the corresponding localized MR spectra of the coconut water reveal that several proton resonances are absent.

Zinc in rheumatic heart valves.

This study included 48 patients with chronic rheumatic heart disease, 60 control subjects for plasma zinc comparison and 20 control specimens of heart valves from postmortem cases of accident deaths. Plasma and cardiac tissue levels of zinc in patients with rheumatic heart disease were significantly lowered compared to controls. Since zinc is important in the synthesis of nucleic acids and proteins it may influence tissue growth, reparative process and structure and function of biomembrane. Low zinc levels may also influence cell mediated immunity and may increase susceptibility of patients to infection and increased rheumatic activity which needs further study.