Chemometric models for toxicity classification based on NMR spectra of biofluids

1H NMR spectroscopic and pattern recognition (PR)-based methods were used to investigate the biochemical variability in urine obtained from control rats and from rats treated with a hydrazine (a model hepatotoxin) or HgCl(2) (a model renal cortical toxin). The 600 MHz (1)H NMR spectra of urine samples obtained from vehicle- or toxin-treated Han-Wistar (HW) and Sprague-Dawley (SD) rats were acquired, and principal components analysis (PCA) and soft independent modeling of class analogy (SIMCA) analysis were used to investigate the (1)H NMR spectral data. Variation and strain differences in the biochemical composition of control urine samples were assessed. Control urine (1)H NMR spectra obtained from the two rat strains appeared visually similar. However, chemometric analysis of the control urine spectra indicated that HW rat urine contained relatively higher concentrations of lactate, acetate, and taurine and lower concentrations of hippurate than SD rat urine. Having established the extent of biochemical variation in the two populations of control rats, PCA was used to evaluate the metabolic effects of hydrazine and HgCl(2) toxicity. Urinary biomarkers of each class of toxicity were elucidated from the PC loadings and included organic acids, amino acids, and sugars in the case of mercury, while levels of taurine, beta-alanine, creatine, and 2-aminoadipate were elevated after hydrazine treatment. SIMCA analysis of the data was used to build predictive models (from a training set of 416 samples) for the classification of toxicity type and strain of rat, and the models were tested using an independent set of urine samples (n = 124). Using models constructed from the first three PCs, 98% of the test samples were correctly classified as originating from control, hydrazine-treated, or HgCl(2)-treated rats. Furthermore, this method was sensitive enough to predict the correct strain of the control samples for 79% of the data, based upon the class of best fit. Incorporation of these chemometric methods into automated NMR-based metabonomics analysis will enable on-line toxicological assessment of biofluids and will provide a tool for probing the mechanistic basis of organ toxicity.

Study of the compositional changes of mango during ripening by use of nuclear magnetic resonance spectroscopy

Liquid-state NMR spectroscopy was used to follow the compositional changes in mango juice during ripening, whereas MAS and HR-MAS techniques enabled resolved (13)C and (1)H NMR spectra of mango pulps to be recorded. Spectral assignment enabled the identification of several organic acids, amino acids, and other minor components, and the compositional changes upon ripening were followed through the changes in the spectra. In pulps, sucrose was found to predominate over fructose and glucose at most ripening stages, and citric acid content decreased markedly after the initial ripening stages while alanine increased significantly. Other spectral changes reflect the complex biochemistry of mango ripening and enabled the role played by some compounds to be discussed. Some differences observed between the composition of juices and pulps are discussed. This work shows that NMR spectroscopy enables the direct characterization of intact mango pulps, thus allowing the noninvasive study of the overall biochemistry in the whole fruit.

Application of directly coupled HPLC-NMR-MS to the identification and confirmation of quercetin glycosides and phloretin glycosides in apple peel

Directly coupled HPLC-NMR-MS was used to identify and confirm the presence of quercetin O-glycosides and phloretin O-glycosides in an extract of apple peel. From the MS and MS/MS data, the molecular weights of the intact molecules as well as those of quercetin and phloretin and their sugar moieties were deduced. The NMR data provided information on the identity of the compounds as well as the alpha and beta conformations and the position of the glycosides on quercetin and phloretin. The following O-glycosides of quercetin could be identified: quercetin-3-alpha-L-rhamnosyl-(1-->6)-beta-D-glucoside (rutin), quercetin-3-beta-D-galactoside (hyperin), quercetin-3-beta-D-glucoside (isoquercitrin), quercetin-3-beta-D-xyloside (reynoutrin), quercetin-3-alpha-L-arabinofuranoside (avicularin), and quercetin-3-alpha-L-rhamnoside (quercitrin). Phloretin was present as phloretin-2'-beta-D-glucoside (phloridzin) and the 2'-beta-D-xylosyl-(1-->6)-beta-D-glucoside. Concentrations were between 0.2 and 5 mg/g of apple peel.

Distinction between normal and renal cell carcinoma kidney cortical biopsy samples using pattern recognition of (1)H magic angle spinning (MAS) NMR spectra

The technique of magic angle spinning (MAS) high resolution (1)H NMR spectroscopy applied to intact tissues provides excellent peak resolution and thus much biochemical information. The use of computer-based pattern recognition techniques to classify human renal cortex tissue samples as normal or tumour based on their (1)H MAS NMR spectra has been investigated. In this preliminary study of 22 paired control and tumour samples, exploratory data analysis using principal components based on NMR spectral intensities showed clear separation of the two classes. Furthermore, using the supervised method of linear discriminant analysis, based on individual data point intensities or on integrated spectral regions, it was possible to distinguish between the normal and tumour kidney cortex tissue with 100% accuracy, including a single example of a metastatic tumour from a primary lung carcinoma. A tumour sample from the collecting duct of the kidney showed a different NMR spectral profile, and pattern recognition indicated that this sample did not classify with the cortical tumours.

[Amputations and mortality in elderly insulin-treated patients with type 2 diabetes]

The diabetic foot syndrome has a strong impact on the morbidity of elderly patients with type 2 diabetes, since diabetics have a 22-fold higher amputation rate. The aim of this study was to conduct a prospective evaluation of elderly insulin-treated patients with type 2 diabetes, giving special consideration to the diabetic foot syndrome. 94 consecutively admitted patients (mean age 68 years; mean diabetes duration 13 years) were re-evaluated 2, 5 and 10 years after participation in a 5-day insulin treatment and teaching programme for patients with type 2 diabetes. During the 10-year follow-up period 60 (64%) patients had died. Of the remaining 34 patients 33 were evaluated personally or by phone. All patients still alive had no acute foot complications and no amputations during the 10-year follow-up period. In these patients an acceptable level of metabolic control and acute metabolic decompensations was found. However, in 55 deceased patients (no data were available for 5 patients) 20 above-knee amputations (1 patient on both legs) and 2 fore-foot amputations were performed. This shows that severe complications as amputations associated with high mortality will be grossly underestimated, unless deceased patients are included in follow-up studies. An improved care for the feet of elderly insulin-treated patients is needed.

High-resolution magic angle spinning 1H NMR spectroscopic studies on intact rat renal cortex and medulla

High-resolution magic angle spinning 1H NMR (MAS-NMR) spectroscopy was used to investigate the biochemical composition of normal renal cortex and renal papilla samples from rats, and results were compared with those from conventional 1H NMR analysis of protein-free tissue extracts. 1H MAS NMR spectra of samples obtained from inner and outer cortex were found to be broadly similar in terms of metabolite profile, and intra- and inter-animal variability was small. However, the MAS NMR spectra from renal papilla samples were qualitatively and quantitatively different from those obtained from cortex. High levels of free amino acids and several organic acids were detected in the cortex, together with choline, glucose, and trimethylamine-N-oxide. The dominant metabolite resonances observed in papillary tissue were from glycerophosphocholine (GPC), betaine, myo-inositol, and sorbitol. On increasing the magic angle spinning rate from 4,200 to 12,000 Hz, the lipid MAS 1H NMR signal profile remained largely unchanged in papillary tissue, whereas "new" resonances from triglycerides appeared in the spectra of cortical tissue, this effect being reversible on returning the spinning rate to 4,200 Hz. Further investigation into the behavior of the lipid components under different spinning rates suggested that the lipids in the cortex were present in more motionally constrained environments than those in the papilla. 1H MAS NMR spectra of tissues are of value both in interrogation of the biochemical composition of whole tissue, and in obtaining information on the mobility and compartmentalization of certain metabolites.

Effect of age on excess mortality in obesity

CONTEXT

The effect of age on excess mortality from all causes associated with obesity is controversial. Few studies have investigated the association between body mass index (BMI, calculated as weight in kilograms divided by the square of height in meters), age, and mortality, with sufficient numbers of subjects at all levels of obesity.

OBJECTIVE

To assess the effect of age on the excess mortality associated with all degrees of obesity.

DESIGN

Prospective cohort study.

SETTING AND PARTICIPANTS

A total of 6193 obese patients with mean (SD) BMI of 36.6 (6.1) kg/m2 and mean (SD) age of 40.4 (12.9) years who had been referred to the obesity clinic of Heinrich-Heine University, Düsseldorf, Germany, between 1961 and 1994. Median follow-up time was 14.8 years.

MAIN OUTCOME MEASURE

All-cause mortality through 1994 among 6053 patients for whom follow-up data were available (1028 deaths) analyzed as standardized mortality ratios (SMRs) using the male-female population of the geographic region (North Rhine Westphalia) as reference.

RESULTS

The cohort was grouped into approximate quartiles according to age (18-29, 30-39, 40-49, and 50-74 years) and BMI (25 to <32, 32 to <36, 36 to <40, and > or =40 kg/m2) at baseline. The SMRs showed a significant excess mortality with an SMR for men of 1.67 (95% confidence interval, 1.51-1.85; P<.001) and an SMR for women of 1.45 (95% confidence interval, 1.34-1.57; P<.001). The excess mortality associated with obesity declined with age. For men, the SMRs of the 4 age groups were 2.46, 2.30, 1.99, and 1.31, respectively; for women, they were 1.81, 2.10, 1.70, and 1.26, respectively (Poisson trend test, P<.001). The SMRs increased with BMI but, within each BMI group, the SMRs decreased with age. The lowest SMRs (for men, 1.01; for women, 0.91) were obtained for patients older than 50 years with BMIs of 25 to less than 32 kg/m2. Thus, older men and women at a BMI range of 25 to less than 32 kg/m2 had no excess mortality. The highest SMRs (for men, 4.22; for women, 3.79) were calculated for the patients aged 18 to 29 years with a BMI of 40 kg/m2 or higher.

CONCLUSIONS

In this large cohort of obese persons, risk of death increased with body weight, but obesity-related excess mortality declined with age at all levels of obesity.

Implications of the traditional and the new ACSM physical activity recommendations on weight reduction in dietary treated obese subjects

OBJECTIVE

To assess the acceptance of the traditional American College of Sports Medicine (ACSM) exercise recommendation (20-60 min of vigorous exercise at least three times per week) and of the new, broader Centers for Disease Control (CDC)/ACSM physical activity recommendation (30 min of moderate intensity activities on most days of the week) in an obese population and to elucidate the implications of meeting these recommendations on weight reduction during dietary treatment.

DESIGN

Prospective dietary intervention study of 1000 kcal diet daily.

SUBJECTS

109 obese subjects (age: 45.6 +/- 13.1 y, body mass index (BMI): 38.1 +/- 6.0 kg/m2, (Female/Male: 81/19%)

MEASUREMENTS

The time spent in moderate (3-6 MET, metabolic equivalents) and vigorous (6-10 MET) physical activities was assessed by use of the Stanford-7-Day-Physical-Activity-Recall-Questionnaire, with subsequent allocation of the subjects to one of three physical activity groups: meeting the traditional recommendation (TR), the new recommendation (NR) or neither of both (SED, sedentary subjects). Physical activity level, physical activity energy expenditure, total energy expenditure (based upon the questionnaire) and resting metabolic rate (by standard equation) were estimated at baseline. Body weight was determined at baseline and after a mean of 16.3 weeks of dietary treatment.

RESULTS

The new, broader recommendation was met by twice as many of the obese subjects (34%) as was the traditional recommendation (17%). Weight reduction at follow up (-8.2 +/- 6.5 kg, 16.3 +/- 4.3 weeks, mean +/- s.d.) was positively correlated with the physical activity level at baseline (r = 0.49, P < 0.001). Meeting either the traditional or the new recommendation was associated with greater weight loss [-11.9 +/- 8.5 kg (TR) and -10.1 +/- 6.4 kg (NR), respectively, not statistically significant (NS)] as compared to being sedentary [-6.5 +/- 5.2 kg (SED), P < 0.05 vs both NR and TR].

CONCLUSIONS

Not only participation in vigorous exercise, but also regular engagement in moderate intensity physical activities, as recently recommended by the CDC/ACSM, predicts greater weight reduction during dietary treatment, compared to being sedentary. The new, broader physical activity recommendation appears to be more readily accepted by obese subjects than the former ACSM recommendation on exercise training.

Development of a model for classification of toxin-induced lesions using 1H NMR spectroscopy of urine combined with pattern recognition

Pattern recognition approaches were developed and applied to the classification of 600 MHz 1H NMR spectra of urine from rats dosed with compounds that induced organ-specific damage in either the liver or kidney. Male rats were separated into groups (n = 5) and each treated with one of the following compounds; adriamycin, allyl alcohol, 2-bromoethanamine hydrobromide, hexachlorobutadiene, hydrazine, lead acetate, mercury II chloride, puromycin aminonucleoside, sodium chromate, thioacetamide, 1,1,2-trichloro-3,3,3-trifluoro-1-propene or dose vehicle. Urine samples were collected over a 7 day time-course and analysed using 600 MHz 1H NMR spectroscopy. Each NMR spectrum was data-reduced to provide 256 intensity-related descriptors of the spectra. Data corresponding to the periods 8-24 h, 24-32 h and 32-56 h post-dose were first analysed using principal components analysis (PCA). In addition, samples obtained 120-144 h following the administration of adriamycin and puromycin were included in the analysis in order to compensate for the late onset of glomerular toxicity. Having established that toxin-related clustering behaviour could be detected in the first three principal components (PCs), three-quarters of the data were used to construct a soft independent modelling of class analogy (SIMCA) model. The remainder of the data were used as a test set of the model. Only three out of 61 samples in the test set were misclassified. Finally as a further test of the model, data from the 1H NMR spectra of urine from rats that had been treated with uranyl nitrate were used. Successful prediction of the toxicity type of the compound was achieved based on NMR urinalysis data confirming the robust nature of the derived model.

Biochemical classification of kidney carcinoma biopsy samples using magic-angle-spinning 1H nuclear magnetic resonance spectroscopy

High resolution 1H nuclear magnetic resonance (NMR) spectra using spinning at the magic angle (1H MAS NMR) have been obtained on intact normal and pathological kidney tissue samples from patients undergoing surgery for renal cell carcinoma (RCC). The spectra were measured on ca. 80 mg samples and provided high resolution 1H NMR spectra in which effects of dipolar couplings, chemical shift anisotropy and magnetic susceptibility differences are minimised thus yielding high spectral resolution. Conventional one-dimensional and spin-echo spectra and two-dimensional J-resolved, TOCSY and 1H-13C HMQC spectra were also measured on selected samples and these allowed the assignment of resonances of endogenous substances comprising both cytosolic and membrane components. The tumour tissues were characterised principally by an increased lipid content. These are the first reported results on human tumour tissues using this technique and the approach offers potential for the rapid classification of different types of tumour tissue.

Assessment of excess mortality in obesity

Quantification of the excess mortality from all causes associated with obesity remains controversial. In this paper, 6,193 obese patients, those with a body mass index (weight (kg)/height (m)2 (BMI)) range of 25-74 kg/m2, recruited from 1961 to 1994 in Düsseldorf, Germany, were followed for a mean time of 14 (standard deviation, 8.2) years, yielding 87,179 observed patient-years. During the study period, 1,028 patients (16.6%) died. The entire cohort was grouped into approximate quartiles according to BMI: group 1, BMI from 25 to < 32; group 2, BMI from 32 to < 36; group 3, BMI from 36 to < 40; group 4, BMI > or = 40 kg/m2. The following risk ratios were estimated by means of Cox proportional hazards models using the lowest BMI group as reference category: group 2 for men, 1.02 (95% confidence interval 0.76-1.37); for women, 1.23 (95% confidence interval 0.96-1.58); group 3 for men, 1.50 (95% confidence interval 1.09-2.06); for women, 1.33 (95% confidence interval 1.03-1.73); and group 4 for men, 2.10 (95% confidence interval 1.53-2.88); for women, 2.25 (95% confidence interval 1.78-2.84). The following standardized mortality ratios were calculated by using the respective geographic area (the Federal State of North Rhine Westphalia) as reference population: group 1 for men, 1.26 (95% confidence interval 0.98-1.61); for women, 1.00 (95% confidence interval 0.81-1.23); group 2 for men, 1.31 (95% confidence interval 1.09-1.57); for women, 1.20 (95% confidence interval 1.02-1.40); group 3 for men, 1.92 (95% confidence interval 1.53-2.38); for women, 1.27 (95% confidence interval 1.07-1.50); and group 4 for men, 3.05 (95% confidence interval 2.47-3.73); for women, 2.31 (95% confidence interval 2.04-2.60). In addition to age, sex, and BMI, Cox proportional hazards models revealed systolic blood pressure, glucose intolerance, diabetes, and smoking as significant independent mortality risk factors, whereas cholesterol was not significant. In this prospective study of a large cohort of obese persons, morbid obesity (BMI of > or = 40 kg/m2) was a strong predictor of premature death. Excess mortality risks associated with gross obesity (BMI from 32 to < 40 kg/m2) were considerably lower than hitherto assumed; moderate degrees of obesity (BMI from 25 to < 32 kg/m2) were not significantly associated with excess mortality.

750 MHz HPLC-NMR spectroscopic identification of rat microsomal metabolites of phenoxypyridines

Directly coupled 750 MHz HPLC-1H NMR spectroscopy has been applied to the characterisation of low level metabolites of 3-amino-2-(2-fluorophenoxy)pyridine (AP) and 3-nitro-2-(2-fluorophenoxy)pyridine (NP) in rat microsomes. In stop-flow HPLC-NMR mode, the direct injection of microsomal extracts enabled the separation and characterisation of minor metabolites. NP is converted into AP to an extent of 93.4% and this is further metabolised to 4- and 6-hydroxy-AP (6 and 0.6% respectively). Unequivocal identification of these metabolites was achieved without the use of a radiolabel or synthetic standards and thus demonstrates the applicability of directly coupled HPLC-NMR to metabolite identification in in vitro systems. The potential exists for HPLC-NMR and HPLC-NMR-MS to provide rapid metabolic information within the timescale of high throughput lead optimisation exercises in drug discovery.

Direct observation of resolved intracellular and extracellular water signals in intact human red blood cells using 1H MAS NMR spectroscopy

High resolution 400 MHz 1H NMR spectra of red blood cell suspensions when measured using magic angle spinning (MAS) show two water resonances separated by 15 Hz. Based on addition of a paramagnetic Mn-EDTA complex, measurement of relaxation times and variation of extracellular H2O/D2O ratios, these have been assigned as intracellular (linewidth 17.5 Hz) and extracellular water (linewidth 4.6 Hz). This is the first direct observation of intracellular water using NMR spectroscopy and the 1H MAS NMR spectroscopic approach offers the possibility of studying directly the compartmentation of substances in cells and kinetics of molecular transport.

750 MHz 1H NMR spectroscopy characterisation of the complex metabolic pattern of urine from patients with inborn errors of metabolism: 2-hydroxyglutaric aciduria and maple syrup urine disease

750 MHz 1H NMR spectroscopy has been used to characterise in detail the abnormal low molecular weight metabolites of urine from two patients with inborn errors of metabolism. One case of the rare condition 2-hydroxyglutaric aciduria has been examined. There is at present no rapid routine method to detect this genetic defect, although NMR spectroscopy of urine is shown to provide a distinctive pattern of resonances. Assignment of a number of prominent urinary metabolites not normally seen in control urine could be made on the basis of their known NMR spectral parameters including the diagnostic marker 2-hydroxyglutaric acid, which served to confirm the condition. In addition, 750 MHz 1H NMR spectroscopy has been used to characterise further the abnormal metabolic profile of urine from a patient with maple syrup urine disease. This abnormality arises from a defect in branched chain keto-acid decarboxylase activity and results in a build up in the urine of high levels of branched chain oxo- and hydroxy-acids resulting from altered metabolism of the branched chain amino acids, valine, leucine and isoleucine. A number of previously undetected abnormal metabolites have been identified through the use of one-dimensional and two-dimensional J-resolved and COSY 750 MHz 1H NMR spectroscopy, including ethanol, 2-hydroxy-isovalerate, 2,3-dihydroxy-valerate, 2-oxo-3-methyl-n-valerate and 2-oxo-isocaproate. NMR spectroscopy of urine, particularly when combined with automatic data reduction and computer pattern recognition using a combination of biochemical markers, promises to provide an efficient alternative to other techniques for the diagnosis of inborn errors of metabolism.

Application of high-field proton nuclear magnetic resonance ( 1 H-NMR) spectroscopy for the analysis of explosives and related compounds in groundwater samples ? a comparison with the high-performance liquid chromatography (HPLC) method

High-field proton nuclear magnetic resonance ((1)H-NMR) spectroscopy was applied to the analysis of nitroaromatics and nitramines in ammunition waste water. The (1)H-chemical shifts data of a variety of reference compounds are presented. Three groundwater samples, taken near the former ammunition plant Elsnig (Saxony), were analysed by high-performance liquid chromatography (HPLC) and by proton nuclear magnetic resonance spectroscopy. The results of HPLC and NMR analyses are compared and discussed.

Direct characterization of drug glucuronide isomers in human urine by HPLC-NMR spectroscopy: application to the positional isomers of 6,11-dihydro-11-oxodibenz[b,e]oxepin-2-acetic acid glucuronide

In this work, 400 and 600 MHz 1H HPLC-NMR spectroscopic methods were developed and applied to separate and identify the positional glucuronide isomers and anomers of the model nonsteroidal antiinflammatory drug, 6,11-dihydro-11-oxodibenz[b,e]oxepin-2-acetic acid, in whole human urine. The HPLC methods utilized either an isocratic system, comprising 30% acetonitrile in water at pH 2.5, or a gradient elution system increasing from 30% to 60% acetonitrile, in order to achieve improved separation of the 2-, 3-, and 4-O-acylglucuronide isomers from the faster eluting endogenous urinary metabolites. Directly coupled stop-flow 1H HPLC-NMR spectroscopic measurements were made at the retention times indicated by the UV-monitored chromatographic peaks. The glucuronide isomers were identified from the 1H NMR spectra on the basis of their chemical shifts and spin-spin coupling patterns. The elution order was 4-O-acyl-, 3-O-acyl-, and finally 2-O-acylglucuronide, with tR values of 10.04, 11.68, and 12.64 min, respectively. Although the alpha- and beta-anomers of each of the positional isomers could not be separated in these solvent systems, they could be identified in the individual 1H NMR spectra. This work shows for the first time that directly coupled HPLC-NMR spectroscopy can be used directly to isolate and characterize acyl-migrated isomers of drug glucuronides in whole urine. This approach will be of value in the study of glucuronide acyl migration reactions of nonsteroidal antiinflammatory drugs and other xenobiotic ester glucuronides in whole biofluids.

Gender does not influence sympathetic neural reactivity to stress in healthy humans

Previous data support the idea of heightened sympathetically mediated cardiovascular reactivity in males. However, definitive conclusions cannot be made because of inconsistent reports, possibly stemming from imprecise measurement of sympathetic activity and/or failure to equate the stress stimuli between genders. The present study tested the hypothesis that males exhibit heightened sympathetic reactivity that is associated with heightened cardiovascular and plasma catecholamine responses. In 37 healthy adults (20 males, 17 females: age = 20-42 yr), direct recordings of skeletal muscle sympathetic nerve activity (MSNA), plasma catecholamines, heart rate, blood pressure, and perceived stress were measured before and during three laboratory stressors (isometric handgrip, cold pressor, and mental arithmetic). MSNA, catecholamine, and cardiovascular reactivity (defined as change from rest) were not consistently different between genders. For the isometric handgrip, when expressed as absolute unit changes, males had larger MSNA responses (P < 0.01), which were partially explained by greater contraction force; they did not differ in terms of percent change from baseline or in perceived stress. The responses to the cold pressor and mental arithmetic tasks were similar between genders. These findings indicate that stress-evoked vasoconstrictor neural excitation and the associated increases in blood pressure are not consistently influenced by gender.

750 MHz HPLC-NMR spectroscopic studies on the separation and characterization of the positional isomers of the glucuronides of 6,11-dihydro-11-oxodibenz[b,e]oxepin-2-acetic acid

Ester glucuronides (beta-1-O-acyl-D-glucopyranuronates) of many drugs can undergo a series of acyl migration reactions, resulting in positional isomers and anomers which can react with serum proteins with possible toxicological consequences. We have investigated the acyl migration of the ester glucuronides of the model drug 6,-11-dihydro-11-oxodibenz[b,e]oxepin-2-acetic acid in pH 7.4 buffer using directly coupled 750 MHz stopped-flow HPLC-NMR spectroscopy. Using a reversed phase isocratic HPLC method with 21% acetonitrile and 79% D2O in the mobile phase, it was possible to separate and hence identify the individual positional isomers of the model drug glucuronide by 750 MHz HPLC-NMR. The order of elution of the isomers from the C18 column was 4alpha-, 4beta-, aglycon, 1beta-, 3beta-, 3alpha-, 2alpha-, 2beta- (alpha- and beta- referring to the anomerization state at C1 on the glucuronide ring and the numbers referring to the carbon number on the glucuronide ring to which the drug moiety has migrated). It is shown that directly coupled ultra-high-field HPLC-NMR spectroscopy offers a unique analytical advantage for obtaining structural information of interconverting compounds in equilibrium mixtures, and this method will be of value in the study of reactive drug glucuronides of toxicological importance.

Lack of relationship between muscle sympathetic nerve activity and skeletal muscle vasodilation in response to insulin infusion

Increases in plasma insulin concentration result in vasodilation in skeletal muscle but also in an increase in muscle sympathetic nerve activity (MSNA) which is thought to cause vasoconstriction. The increase in MSNA could therefore be a response to vasodilation (baroreflex), or MSNA could cause vasodilation via putative sympathetic vasodilatory fibres. To examine the relationship between vasodilation, MSNA and insulin action we studied nine non-diabetic Pima Indian men (age 29 +/- 7 years, weight 91 +/- 19 kg, 29 +/- 6% body fat, mean +/- SD) during sequential euglycaemic clamps at low and high insulin doses (80 and 600 mU.m-2.min-1). Leg blood flow was measured by thermodilution, leg glucose uptake by the balance technique, arterial pressure by invasive monitoring and MSNA by microneurography of the peroneal nerve. Whole body glucose uptake (M) ranged from 6.7 to 48.3 during low dose and from 9.4 to 67.7 mumol kg fat free mass-1.min-1 during high dose insulin infusion. At both insulin doses, incremental leg blood flow correlated with M (r = 0.63 and 0.71, respectively). No correlation was found between incremental MSNA and leg blood flow, M or leg glucose uptake. Blood pressure was unchanged throughout the study. MSNA increased after 15-40 min of insulin infusion in all the subjects, whereas leg blood flow started to increase only after 45 min in the most insulin sensitive but not in the most insulin resistant subjects. Thus, insulin stimulates MSNA more rapidly than vasodilation. In conclusion, insulin-mediated MSNA: 1) is neither a response to nor a cause of the vasodilation observed in insulin sensitive men, 2) has no net pressor effect even in the most insulin resistant men in whom insulin-mediated vasodilation was impaired. We conclude that the effect of insulin to stimulate MSNA is dissociated from its acute haemodynamic action.

Assignment of the 750 MHz 1H NMR resonances from a mixture of transacylated ester glucuronic acid conjugates with the aid of oversampling and digital filtering during acquisition

Many drugs containing carboxylic acid functional groups are metabolised in vivo to ester glucuronides (1-O-acyl-beta-D-glucopyranuronates) and, of these, a number show a propensity to undergo internal isomerisation via a transacylation process, causing the carboxylic acid moiety to migrate successively to the 2-, 3- and 4-positions of the glucuronic acid. These products may be responsible, through reactions with plasma proteins, for some of the allergenic side effects in a number of non-steroidal anti-inflammatory drugs. It is important to understand those properties of the drug molecules which facilitate this reaction, and to this end we have studied the transacylation product formation and reaction kinetics in a series of aryl carboxylic acid glucuronides using NMR spectroscopy. However, the resulting 1H NMR spectra are very complex with much resonance overlap, and recourse to spectral simplification processes is necessary. Here, improvement in spectral resolution by oversampling and digital filtering to restrict the detection range of the spectrometer, thus yielding improved digital resolution, is demonstrated. The approach has been applied to the assignment of a mixture of transacylated ester glucuronides of 2-trifluoromethylbenzoic acid through the use of a two-dimensional 1H-1H TOCSY experiment.

Daily energy expenditure in male endurance athletes with differing energy intakes

The 24-h energy expenditure (24-h EE), resting EE (REE), sleeping EE (SEE), and spontaneous physical activity (SPA) were compared between six male endurance athletes whose reported energy intake was low (LOW) and did not match that theoretically required for weight maintenance and four whose reported energy intake appeared adequate (ADQ) and matched their estimated EE. Groups did not differ in age, body weight, fat-free mass, and daily EE estimated from activity records. The LOW athletes reported an energy intake 6338 +/- 2164 kJ.d-1 less than estimated EE. The 24-h EE, REE, SEE, and SPA of the LOW athletes were significantly lower than the ADQ athletes (862, 523, 770 kJ.d-1, and 43 min.d-1, respectively). Using all subjects, there was a significant positive correlation between REE and free thyroxine (FT4) (r = 0.82) and SEE and FT4 (r = 0.66). Thus, part of the LOW athlete's ability to maintain body weight on a seemingly low energy intake appears due to a lower daily sedentary EE.

750 MHz 1H and 1H-13C NMR spectroscopy of human blood plasma

High-resolution 750 MHz 1H NMR spectra of control human blood plasma have been measured and assigned by the concerted use of a range of spin-echo, two-dimensional J-resolved, and homonuclear and heteronuclear (1H-13C) correlation methods. The increased spectral dispersion and sensitivity at 750 MHz enable the assignment of numerous 1H and 13C resonances from many molecular species that cannot be detected at lower frequencies. This work presents the most comprehensive assignment of the 1H NMR spectra of blood plasma yet achieved and includes the assignment of signals from 43 low M(r) metabolites, including many with complex or strongly coupled spin systems. New assignments are also provided from the 1H and 13C NMR signals from several important macromolecular species in whole blood plasma, i.e., very-low-density, low-density, and high-density lipoproteins, albumin, and alpha 1-acid glycoprotein. The temperature dependence of the one-dimensional and spin-echo 750 MHz 1H NMR spectra of plasma was investigated over the range 292-310 K. The 1H NMR signals from the fatty acyl side chains of the lipoproteins increased substantially with temperature (hence also molecular mobility), with a disproportionate increase from lipids in low-density lipoprotein. Two-dimensional 1H-13C heteronuclear multiple quantum coherence spectroscopy at 292 and 310 K allowed both the direct detection of cholesterol and choline species bound in high-density lipoprotein and the assignment of their signals and confirmed the assignment of most of the lipoprotein resonances.

Racial difference in body core temperature between Pima Indian and Caucasian men

A low body temperature is associated with a low metabolic rate for a given body size and body composition. These two traits might have been assets in the history of a population subjected to cycles of feast and famine, but became part of an obesity-prone syndrome in our westernized society characterized by plenty of food and a sedentary lifestyle. We tested whether Pima Indians have lower body temperatures than Caucasians, a trait which might partly explain the high prevalence of obesity in this population. Twenty-five Pima Indian (28 +/- 6 yrs, 87.8 +/- 22.8 kg, 29 +/- 9% body fat) and 25 Caucasian (30 +/- 5 yrs, 80.7 +/- 18.4 kg, 22 +/- 11% body fat) men had body core temperatures measured by telemetry for 24 h while in a respiratory chamber. Mean daily body core temperature was 36.93 +/- 0.12 and 36.90 +/- 0.22 degrees C in Pima Indians and Caucasians, respectively. Since body core temperature during sleep (SLBCT) correlated with percentage body fat, a subset of 10 Pima Indians and 10 Caucasians were pair-matched for body weight and percentage body fat. In this group, SLBCT was lower in Pima Indians than in Caucasians (36.45 +/- 0.10 vs 36.65 +/- 0.27 degrees C; P < 0.01) and, ethnic group accounted for 20% of the variance in SLBCT (P < 0.01). Surprisingly, the lower SLBCT was not associated with a low metabolic rate and therefore does not seem to play a role in the etiology of obesity in Pima Indians.(ABSTRACT TRUNCATED AT 250 WORDS)