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PubMed2006

Hepatic lipid accumulation in healthy subjects: a comparative study using spectral fat-selective MRI and volume-localized 1H-MR spectroscopy.

Fat-selective MRI was applied to assess the amount and spatial distribution of hepatic lipids (HL) in healthy subjects. The results were compared with those obtained by localized 1H-MR spectroscopy (MRS). Ninety subjects (23-63 years old) underwent single-slice fat-selective MRI with spatial-spectral excitation and volume-localized spectroscopy at 1.5 T. HLs were analyzed in ventral and dorsal regions of interest (ROIs) of the liver in fat-selective images. Spectra were evaluated using the integral signal of methylene and methyl signals. The fat-selective images showed smooth and homogeneous distribution of HL over the entire cross section of the liver. There was, however, a marked interindividual variability in the amount of HL. MRS revealed a lipid signal fraction between 0.5% and 39.3%. The fat content in the ROIs in images correlated well with the spectroscopic results (r >or= 0.95). Both techniques provide sufficient sensitivity for a reliable and quantitative assessment of liver steatosis in subjects without liver disease. 1H-MRS has a higher sensitivity compared to MRI, especially for small amounts of HL, which may be of interest for metabolic interventions. Fat-selective images provide more spatial information about fat distribution, which makes this technique suitable for clinical imaging of patients with liver disease.

Adult↗

PubMed1979

Effects of alloxan on glucose-stimulated insulin secretion, glucose metabolism, and cyclic adenosine 3', 5'-monophosphate levels in rat isolated islets of langerhans.

Insulin secretion was stimulated and cyclic adenosine 3', 5'-monophosphate (cAMP) levels were elevated in isolated rat islets by 27.5 mmol/l glucose. Alloxan caused a dose-dependent decrease in both variables with complete obliteration of insulin release at a concentration of 1.25 mmol/l. D-glucose, in the presence or absence of extracellular calcium, or 3-0-methyl-D-glucose (both at 27.5 mmol/l) protected completely against the effects of alloxan on both glucose-induced insulin release and cAMP Levels. 3-0-Methylglucose did not stimulate insulin secretion or elevate cAMP and did not interfere with glucose-stimulated secretion or elevation of cAMP. When glucose-stimulated insulin release was abolished by alloxan, the metabolism of glucose, determined by the rate of 3H2O formation from [5-3H] glucose, was depressed by 20%. It is concluded that alloxan altered the adenylate cyclase system such that it could no longer be stimulated by glucose. Glucose-stimulated insulin secretion or elevation of cAMP did not appear essential for glucose to protect against alloxan. Protection by 3-0-methylglucose did not appear to be mediated through an alteration of cAMP metabolism. Alloxan did not inhibit glucose-induced insulin secretion by grossly altering glycolysis.

Alloxan↗

PubMed2004

Negative and positive effects of an IAP-LTR on nearby Pcdaalpha gene expression in the central nervous system and neuroblastoma cell lines.

Intracisternal A-particles (IAPs) are defective retrovirions encoded by members of a large family of endogenous proviral elements in the murine genome. An intact IAP element was found in the protocadherin alpha (Pcdhalpha) gene cluster of five laboratory mouse strains. However, IAP insertion was not detected in three wild mouse strains we investigated. This IAP insertion caused the disruption of one variable exon of laboratory mouse and down-regulated expression of the Pcdhalpha v8 exon, which is located just downstream of the IAP in the brain following the methylation of 5' regulatory region of Pcdhalpha v8. In contrast, the Pcdhalpha v8 exon was highly expressed in mouse neuroblastoma cell lines. This suggested that the IAP insertion activates the expression of the nearby Pcdhalpha v8 exon in these cell lines. In fact, the Pcdhalpha v8 exon expression was driven by the IAP-long terminal repeat (LTR) following the de-methylation of 5' regulatory region of Pcdhalpha v8. To investigate the promoter activity of the IAP, we constructed an IAP-LTR-ECFP reporter gene and introduced it into neuroblastoma, melanoma, lymphoma, and plasmacytoma cell lines. Interestingly, ECFP-positive cells were observed only in the neuroblastoma cell lines. Moreover, there were no differences in the promoter activities of the IAP-LTR whether it was in the sense or complimentary orientation. Thus, this IAP-LTR has negative and positive regulation on near by gene expression in the brain and neuroblastoma cell lines.

Animals↗

PubMed2002

Kinetic-spectrophotometric determination of ascorbic acid by inhibition of the hydrochloric acid-bromate reaction.

A new analytical method was developed for the determination of ascorbic acid in fruit juice and pharmaceuticals. The method is based on its inhibition effect on the reaction between hydrochloric acid and bromate. The decolourisation of Methyl Orange by the reaction products was used to monitor the reaction spectrophotometrically at 510 nm. The linearity range of the calibration graph depends on bromate concentration. The variable affecting the rate of the reaction was investigated. The method is simple, rapid, relatively sensitive and precise. The limit of detection is 7.6 x 10(-6) M and calibration rang is 8 x 10(-6)-1.2 x 10(-3) M ascorbic acid. The relative standard deviation of seven replication determinations of 8 x 10(-6) and 2 x 10(-5) M ascorbic acid was 2.8 and 1.7%, respectively. The influence of potential interfering substance was studied. The method was successfully applied for the determination of ascorbic acid in pharmaceuticals.

Ascorbic Acid↗

PubMed1999

Effect of pH and temperature on comparative nonenzymatic browning of proteins produced by oxidized lipids and carbohydrates.

Bovine serum albumin (BSA) was incubated for 24 h in the presence of 10 mM ribose (RI), methyl linoleate hydroperoxides, or the secondary products of methyl linoleate oxidation (SP), at five temperatures (25, 37, 50, 80, and 120 degrees C) and different pHs (4, 7, and 10), to study the influence of these variables in the browning, fluorescence, amino acid losses, and pyrrolization of the modified proteins. All treated proteins exhibited similar colors and fluorescence spectra, and the spectra of their Ehrlich adducts were also analogous. However, at 25-50 degrees C the proteins treated with oxidized lipids exhibited higher color changes, amino acid losses, and pyrrolization than the BSA treated with RI, and these effects were much higher in proteins treated with RI at 80-120 degrees C. The effect of pH was similar in proteins treated with RI or SP. These results suggested a similarity for browned proteins obtained from both carbohydrates and oxidized lipids. In addition, both reactions seem to be complementary, because melanoidin formation derived from oxidized lipids can be produced under conditions different from those carbohydrate/protein reactions.

Carbohydrates↗

PubMed2006

Characterization of tunneling systems in molecular versus polymer glasses by high-pressure photon echo spectroscopy.

Intrinsic differences between tunneling two-level systems (TLSs) in molecular versus polymeric glasses are revealed by studying the effect of compression on TLS dynamics. Photon echo studies under variable low-temperature (1.1-2.3 K) and high-pressure (0-30 kbar) conditions have been performed to contrast the effect of compression on molecular [2-methyl-tetrahydrofuran (2MTHF)] versus polymer [Polymethylmethacrylate (PMMA)] glasses. The pressure-induced reduction in the magnitude of the optical dephasing rate of rhodamine 640 in a molecular glass (2MTHF) is found to be comparable to the volume decrease of the glass (e.g., approximately 20% at 30 kbar), indicating that TLSs in 2MTHF are associated with void space or low-density regions of the glass. In contrast, the relative pressure insensitivity observed for organic polymer glasses (PMMA) supports the idea that these TLSs are associated with side chain defects. The power-law exponent for the temperature-dependent dephasing in 2MTHF also decreased significantly at high pressure, suggesting a change in the form of the TLS density of states upon compression of the molecular glass.

Journal Article↗

PubMed1988

Conformational analysis of 9beta,19-cyclopropyl sterols: Detection of the pseudoplanar conformer by nuclear Overhauser effects and its functional implications.

Nuclear Overhauser difference spectroscopy and variable temperature studies of the 9beta,19-cyclopropyl sterols 24,25-dehydropollinastanol (4,4-desmethyl-5alpha-cycloart-24-en-3beta-ol) and cyclolaudenol [(24S)-24-methyl-5alpha-cycloart-25(27)-en-3beta-ol] have shown the solution conformation of the B/C rings to be twist-chair/twist-boat rather than boat/chair as suggested in the literature. This is very similar to the known crystal structure conformation of 9beta,19-cyclopropyl sterols. The effect of these conformations on the molecular shape is highly significant: the first conformation orients into a pseudoplanar or flat shape analogous to lanosterol, whereas the latter conformation exhibits a bent shape. The results are interpreted to imply that, for conformational reasons, cyclopropyl sterols can be expected to maintain the pseudoplanar shape in membrane bilayers.

Journal Article↗

PubMed1986

A video imaging technique for assessing dermal exposure. II. Fluorescent tracer testing.

Laboratory and field evaluations were conducted to determine the suitability of employing a fluorescent tracer in conjunction with video imaging analysis to measure dermal exposure during pesticide applications. The Fluorescent Whitening Agent 4-methyl-7-diethylaminocoumarin and the organophosphate malathion were highly correlated (r = .985) when sprayed under controlled conditions. Deposition levels during field studies were correlated similarly (r = .942); however, variability in deposition ratios requires that field sampling be conducted to determine the ratio for a particular application. Penetration of the two compounds through cotton/polyester workshirt material demonstrated a high correlation (r = .979), whereas penetration of cotton/polyester coverall material was more variable (r = .834). The slopes of the regression lines for the two materials were not significantly different. The ratio of pesticide and tracer recovered from targets was consistently higher than the initial tank ratio due to differences in solubility and mixing.

Computers↗

PubMed2005

Pesticide residues on the external surfaces of field crop sprayers: occupational exposure.

There is a general perception, amongst farmers and researchers, that post-application residues on the external surfaces of sprayers are negligible compared with residues remaining on the internal surfaces, although there have been few attempts to verify this assumption. The aim of this study was to investigate, using cotton glove sampling, operator exposure resulting from three typical operations: entering and working in the cab, general handling of the sprayer and maintenance practices. Samples were analysed for azoxystrobin, carbendazim, chlorothalonil, cyanazine, cypermethrin, epoxiconazole, flusilazole, isoproturon, kresoxim-methyl, metazachlor, pendimethalin, pirimicarb and tebuconazole. Isoproturon, pendimethalin, chlorothalonil and carbendazim were detected >1 mg per glove pair on the cotton gloves, but on the whole there was variability in residue levels between and within compounds. Comparison of results with occupational exposure limits indicated that residues were such that they may not necessarily be considered insignificant. It may therefore be prudent to develop more efficient methods for the external decontamination of sprayers and/or raise awareness of the findings.

Agriculture↗

PubMed2000

Linoleic acid conjugation by human intestinal microorganisms is inhibited by glucose and other substrates in vitro and in gnotobiotic rats.

The anticarcinogen conjugated linoleic acid (CLA) is a product of bacterial activity that isomerizes linoleic acid (LA) in the rumen of herbivores. Therefore, fatty dairy products in the human diet are enriched with CLA. Although bacteria capable of in vitro LA conjugation were detected in the human intestinal tract, CLA synthesis from dietary sunflower seed oil was not observed in gnotobiotic rats associated with these intestinal bacteria. The objective of the study was to investigate variables that affect LA conjugation. In vitro, LA conjugation was strongly inhibited by glucose and other substrates. Concentrations of 1.5 mmol glucose/L inhibited LA conjugation by 50%. Methyl-alpha-D-glucoside was a less effective inhibitor than glucose, and 2-deoxy-D-glucose did not inhibit LA conjugation at all. To analyze the concentration of carbohydrates in intestinal contents, the LA-conjugating bacterial mixed culture and human fecal microorganisms were introduced into germ-free rats. Samples of feces and cecum and colon contents of both groups exhibited in vitro LA-conjugating activity. Rats associated with human intestinal microorganisms contained 5.7 +/- 1. 3 mmol glucose/L in the cecal contents and 6.6 +/- 1.0 mmol glucose/L in the colonic contents. Rats associated with CLA-producing bacterial culture contained 3.4 +/- 1.3 mmol glucose/L in the cecal contents and 4.2 +/- 1.0 mmol glucose/L in the colonic contents. These values are within a range that may explain the observed inhibition of LA conjugation in vivo.

Animals↗

PubMed1982

The effects of cyclic dicarboxylic acids on spontaneous and amino acid-evoked activity of rat cortical neurones.

1 A series of cyclic dicarboxylic acids were applied by microiontophoresis to neurones in the cerebral cortex of rats anaesthetized with urethane. The object was to examine effects on spontaneous firing rates and any ability to antagonize responses to excitatory amino acids. 2 At relatively low ejecting currents (10-25 nA) cis-2,3-piperidine dicarboxylic acid (cis-2,3-PDA) had no effect on spontaneous firing but selectively antagonized the excitation evoked by n-methyl-D-aspartate (NMDA) without affecting responses to quisqualaife or kainate. At higher ejecting currents (60-100 nA) responses to all three agonists were reduced. 3 Other cis-piperidine dicarboxylic acids and piperazine-2,3-dicarboxylic acid had only weak and variable effects on cell firing and responses to NMDA, quisqualate, kainate, glutamate and aspartate. 4 2, 3-Pyridine dicarboxylic acid (quinolinic acid) produced excitation of all cortical neurones tested. 5 2-Amino-5-phosphono-valeric acid, an NMDA antagonist, reduced responses to quinolinate, implying that this compound can act at NMDA receptors. 6 It is suggested that quinolinic acid may be of physiological interest as a potential endogenous excitant in the nervous system and that cis-2,3-PDA and its N-methyl derivative may be of use in studies of receptor pharmacology and the identification of synaptic transmitters.

Amino Acids↗

PubMed1978

Relationship between blood pH and potassium and phosphorus during acute metabolic acidosis.

Metabolic acidosis is known to be associated with increased blood potassium and phosphorus concentrations but the influence of mineral versus nonmineral acids on these variables remains undefined. Therefore, we infused anesthetized mongrel dogs with 0.45% saline (controls), the mineral acids HCl and NH4Cl, and the nonmineral acids lactic, beta-hydroxybutyric and methyl malonic for 1-3 h. Administration of both mineral acids was associated with significant increases in plasma potassium. In contrast, infusion of the three monmineral acids did not result in increases in plasma potassium; in fact, the levels decreased initially in the majority of the dogs. Phosphorus concentrations were increased by lactic and beta-hydroxybutric acids, were unchanged by NH4Cl and HCl, and were decreased by methyl malonic acid. Although the mechanisms responsible for these changes remain to be elucidated, the findings indicate that short-duration infusion of mineral and nonmineral acids has substantially different effects on plasma concentrations of these predominantly intracellular ions.

Acidosis↗

PubMed2005

Poor survival associated with the BRAF V600E mutation in microsatellite-stable colon cancers.

The BRAF V600E mutation has been associated with microsatellite instability and the CpG island methylator phenotype (CIMP) in colon cancer. We evaluated a large population-based sample of individuals with colon cancer to determine its relationship to survival and other clinicopathologic variables. The V600E BRAF mutation was seen in 5% (40 of 803) of microsatellite-stable tumors and 51.8% (43 of 83) of microsatellite-unstable tumors. In microsatellite-stable tumors, this mutation was related to poor survival, CIMP high, advanced American Joint Committee on Cancer (AJCC) stage, and family history of colorectal cancer [odds ratio, 4.23; 95% confidence interval (95% CI), 1.65-10.84]. The poor survival was observed in a univariate analysis of 5-year survival (16.7% versus 60.0%; P < 0.01); in an analysis adjusted for age, stage, and tumor site [hazard rate ratio (HRR), 2.97; 95% CI, 2.05-4.32]; in stage-specific, age-adjusted analyses for AJCC stages 2 to 4 (HRR, 4.88, 3.60, and 2.04, respectively); and in Kaplan-Meier survival estimates for AJCC stages 2 to 4 (P < 0.01 for all three stages). Microsatellite-unstable tumors were associated with an excellent 5-year survival whether the V600E mutation was present or absent (76.2% and 75.0%, respectively). We conclude that the BRAF V600E mutation in microsatellite-stable colon cancer is associated with a significantly poorer survival in stages 2 to 4 colon cancer but has no effect on the excellent prognosis of microsatellite-unstable tumors.

Aged↗

PubMed1985

The constant plasma 18-hydroxycorticosterone to aldosterone ratio: an expression of the efficacy of corticosterone methyloxidase type II activity in disorders with variable aldosterone production.

Aldosterone and 18-hydroxycorticosterone (18-OHB) are produced by the adrenocortical zona glomerulosa. Under normal conditions, plasma 18-OHB levels parallel and are influenced by the same trophic factors that regulate aldosterone production. To evaluate corticosterone-methyl-oxidase II activity, the final step of aldosterone biosynthesis, in conditions associated with chronic derangements of the pituitary-adrenal and/or renal-adrenal axis, we measured the plasma 18-OHB to aldosterone ratio, cortisol, PRA or plasma renin concentration, and potassium (K) in 104 such patients and 15 normal subjects. The 18-OHB to aldosterone ratios in the pituitary-adrenal group were not significantly different from normal regardless of elevated or reduced ACTH and/or cortisol levels [patients with Cushing's syndrome, 3.55 +/- 0.68 (+/-SE); ACTH deficiency, 2.03 +/- 0.34; 21-hydroxylase deficiency, 3.09 +/- 0.23; normal subjects, 2.50 +/- 0.15]. The renal-adrenal group also had normal ratios regardless of plasma renin concentration and K levels [patients with aldosterone-producing adenomas, 2.85 +/- 0.15; idiopathic hyperaldosteronism, 2.14 +/- 0.19; salt-losing nephropathy, 3.06 +/- 0.54; Bartter's syndrome, 2.89 +/- 0.20; isolated (hyporeninemic) hypoaldosteronism, 3.20 +/- 0.39]. Only in patients with 17 alpha-hydroxylase deficiency (230.1 +/- 118.6) was the ratio abnormally high. Chronic perturbations of aldosterone production by ACTH, the renin-angiotensin system, and/or K did not alter this last step of aldosterone biosynthesis (corticosterone-methyloxidase II), as defined by their plasma concentrations. Any influence of these trophic factors must be proximal to the site of 18-OHB production.

18-Hydroxycorticosterone↗

PubMed1994

Method validation in relation to accuracy and precision for the gas chromatography-mass spectrometric analysis of 19-nortestosterone in urine with heptafluorobutyric anhydride and N-methyl-N-(trimethylsilyl)trifluoroacetamide.

Method validation for all the analytical methods used in food control is of the highest priority. For this control there is a lack of reference materials, thus, it is necessary to validate the methods each time they are used for new applications. Among the many aspects of validation, this report pays particular attention to repeatability and reproducibility. The within-assay variability gives a good indication of the precision of the method shown by the repeatability. The between-assay variability gives no indication on the accuracy (or trueness) because no certified reference material is available. The reproducibility however, also gives an indication of the precision of the method. In this work the limit of detection, also an aspect of validation, was found to be below 0.375 micrograms 1-1 for both derivatization methods; however, the precision of the heptafluorobutyric anhydride method was found to be better than that of the N-methyl-N-(trimethylsilyl)trifluoroacetamide method.

Acetamides↗

PubMed1986

Symptoms and behavioral features induced by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) in an old Java monkey [Macaca cynomolgus fascicularis (Raffles)].

The study concerns symptoms and behavioral characteristics induced by MPTP in a 20-year-old Macaca cynomolgus fascicularis, their evolution over 7 months, and the animal's response to 1-dopa treatment. The symptoms which the animal developed include those that have been described earlier in Macaca mulatta and Saimiri sciureus, i.e., rigidity, action tremor, postural tremor, postural flexion, hypokinesia, and bradykinesia. In addition, however, the animal developed a 3.8 Hz resting tremor which in humans is pathognomonic of Parkinson's disease, as well as cogwheeling, the glabellar tap sign, drooling, impaired ability to relax, and many other symptoms. Also unlike previously described MPTP monkeys, the animal's symptoms neither improved spontaneously, nor did they remain stable shortly after MPTP injection. Instead, symptoms steadily progressed to reach a severe status 2 months after MPTP, and further progression was apparent after another 5 months. Therapeutic responses to 1-dopa required accumulation of or kindling by the 100 mg unit doses that were spaced 4 hr apart, were often organized in time as ON episodes that alternated with OFF episodes, and were associated with dyskinesias and bizarre behavior. Of particular interest is that the animal showed kinesia paradoxa which, in humans, constitutes a feature that is unique to Parkinson's disease among the extrapyramidal disorders. In addition to available evidence, the present findings validate the syndrome induced by MPTP in monkey as an animal analogue of Parkinson's disease. Taxonomic category, age, and the occurrence of shock in response to MPTP are discussed as variables that may possibly co-determine the pathology which MPTP may induce in monkey.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗

PubMed2000

Nonlinear dynamics of heart rate variability during experimental hemorrhage in ketamine-anesthetized rats.

Indexes of heart rate variability (HRV) based on linear stochastic models are independent risk factors for arrhythmic death (AD). An index based on a nonlinear deterministic model, a reduction in the point correlation dimension (PD2i), has been shown in both animal and human studies to have a higher sensitivity and specificity for predicting AD. Dimensional reduction subsequent to transient ischemia was examined previously in a simple model system, the intrinsic nervous system of the isolated rabbit heart. The present study presents a new model system in which the higher cerebral centers are blocked chemically (ketamine inhibition of N-methyl-D-aspartate receptors) and the system is perturbed over a longer 15-min interval by continuous hemorrhage. The hypothesis tested was that dimensional reduction would again be evoked, but in association with a more complex relationship between the system variables. The hypothesis was supported, and we interpret the greater response complexity to result from the larger autonomic superstructure attached to the heart. The complexities observed in the nonlinear heartbeat dynamics constitute a new genre of autonomic response, one clearly distinct from a hardwired reflex or a cerebrally determined defensive reaction.

Anesthesia↗

PubMed2004

Field and laboratory arsenic speciation methods and their application to natural-water analysis.

The toxic and carcinogenic properties of inorganic and organic arsenic species make their determination in natural water vitally important. Determination of individual inorganic and organic arsenic species is critical because the toxicology, mobility, and adsorptivity vary substantially. Several methods for the speciation of arsenic in groundwater, surface-water, and acid mine drainage sample matrices using field and laboratory techniques are presented. The methods provide quantitative determination of arsenite [As(III)], arsenate [As(V)], monomethylarsonate (MMA), dimethylarsinate (DMA), and roxarsone in 2-8 min at detection limits of less than 1 microg arsenic per liter (microg As L(-1)). All the methods use anion exchange chromatography to separate the arsenic species and inductively coupled plasma-mass spectrometry as an arsenic-specific detector. Different methods were needed because some sample matrices did not have all arsenic species present or were incompatible with particular high-performance liquid chromatography (HPLC) mobile phases. The bias and variability of the methods were evaluated using total arsenic, As(III), As(V), DMA, and MMA results from more than 100 surface-water, groundwater, and acid mine drainage samples, and reference materials. Concentrations in test samples were as much as 13,000 microg As L(-1) for As(III) and 3700 microg As L(-1) for As(V). Methylated arsenic species were less than 100 microg As L(-1) and were found only in certain surface-water samples, and roxarsone was not detected in any of the water samples tested. The distribution of inorganic arsenic species in the test samples ranged from 0% to 90% As(III). Laboratory-speciation method variability for As(III), As(V), MMA, and DMA in reagent water at 0.5 microg As L(-1) was 8-13% (n=7). Field-speciation method variability for As(III) and As(V) at 1 microg As L(-1) in reagent water was 3-4% (n=3).

Arsenic↗