bluuebunny/crossref_metadata_2025 huggingface dataset:
Reactions of fatty materials with oxygen. XVIII. Catalytic hydrogenation of autoxidized methyl oleate and oleic acid. Preparation of monohydroxystearic acids
Authors: Coleman Joseph E. , Swern Daniel
Published: June 2007

Autoxidation of methyl oleate and oleic acid beyond the peak peroxide values followed by catalytic hydrogenation gave mixed monohydroxystearic acids in high yield. The complicated autoxidation mixture which contains peroxides, hydroxy, carbonyl, and oxirane compounds was simplified considerably in composition by this procedure.

For complete reduction of the double bond, and the carbonyl and oxirane groups, hydrogenation was conducted at about 150° and 150 lbs.. Peroxides were reduced at room temperature. Catalysts used were palladium on carbon and Raney nickel.

The selective reduction of peroxides in autoxidation mixtures has been studied by chemical and catalytic means. Peroxides were converted largely to carbonyl compounds rather than to the anticipated hydroxy compounds. Palladium‐lead on calcium carbonate is an excellent catalyst for reducing peroxides with hydrogen.

tert‐Butyl hydroperoxide, 12‐ ketostearic acid, stearone,cis‐9,10‐epoxystearic acid and methyl oleate peroxide concentrate were employed as model substances in determining hydrogenation conditions.
Composition of liver fats of mature and embryo sharks (galeocerdo tigrinus)
Authors: Pathak S. P. , Suwal P. N.
Published: June 2007

Two liver fats, one from the “mother” and the other from the “embryo” shark (Galeocerdo tigrinus), have been studied. Their component fatty acids are reported.

The mixed fatty acids from each of the fats were first resolved into groups of acids of varying unsaturation by the lithium salt acetone and/or lead salt alcohol methods. The methyl esters of each of these groups of acids were fractionated through the Longenecker's E.H.P. column.

The two fats are found to belong to the fourth group of Tsujimoto's classification of the Elasmobranch fish liver fats. The “mother” shark liver fat contains 43.3% saturated and 56.7% unsaturated acids. The “embryo” shark liver fat contains 39.1% saturated and 60.9% unsaturated acids. Palmitic acid was about 25% in both of the fats.

A possible explanation for the less unsaturation and the absence of higher polyethenoids in the “embryo” liver fat is given.
Streptococcus pneumoniae-associated hemolytic uremic syndrome
Authors: Copelovitch Lawrence , Kaplan Bernard S.
Published: June 2007

Streptococcus pneumonia-associated hemolytic uremic syndrome (HUS) (pneumococcal HUS) is an uncommon condition mainly observed in young children. Early recognition is critical, because of the potential to improve morbidity and mortality. In our review we summarize the pathophysiology, clinical features, diagnostic difficulties and management of this potentially under-diagnosed condition.
Higher-Order Approximations to the Distributions of Fit Indexes Under Fixed Alternatives in Structural Equation Models
Authors: Ogasawara Haruhiko
Published: June 2007

Higher-order approximations to the distributions of fit indexes for structural equation models under fixed alternative hypotheses are obtained in nonnormal samples as well as normal ones. The fit indexes include the normal-theory likelihood ratio chi-square statistic for a posited model, the corresponding statistic for the baseline model of uncorrelated observed variables, and various fit indexes as functions of these two statistics. The approximations are given by the Edgeworth expansions for the distributions of the fit indexes under arbitrary distributions. Numerical examples in normal and nonnormal samples with the asymptotic and simulated distributions of the fit indexes show the relative inappropriateness of the normal-theory approximation using noncentral chi-square distributions. A simulation for the confidence intervals of the fit indexes based on the normal-theory Studentized estimators under normality with a small sample size indicates an advantage for the approximation by the Cornish–Fisher expansion over those by the noncentral chi-square distribution and the asymptotic normality.
The Local Minima Problem in Hierarchical Classes Analysis: An Evaluation of a Simulated Annealing Algorithm and Various Multistart Procedures
Authors: Ceulemans Eva , Van Mechelen Iven , Leenen Iwin
Published: June 2007

Hierarchical classes models are quasi-order retaining Boolean decomposition models for N-way N-mode binary data. To fit these models to data, rationally started alternating least squares (or, equivalently, alternating least absolute deviations) algorithms have been proposed. Extensive simulation studies showed that these algorithms succeed quite well in recovering the underlying truth but frequently end in a local minimum. In this paper we evaluate whether or not this local minimum problem can be mitigated by means of two common strategies for avoiding local minima in combinatorial data analysis: simulated annealing (SA) and use of a multistart procedure. In particular, we propose a generic SA algorithm for hierarchical classes analysis and three different types of random starts. The effectiveness of the SA algorithm and the random starts is evaluated by reanalyzing data sets of previous simulation studies. The reported results support the use of the proposed SA algorithm in combination with a random multistart procedure, regardless of the properties of the data set under study.
Moderate Dietary Intake of Myristic and Alpha‐Linolenic Acids Increases Lecithin‐Cholesterol Acyltransferase Activity in Humans
Authors: Vaysse‐Boué Carole , Dabadie Henry , Peuchant Evelyne , Le Ruyet Pascale , Mendy François , Gin Henry , Combe Nicole
Published: June 2007

Cholesterol removal from tissues into HDL depends on the activity of lecithin‐cholesterol acyltransferase (LCAT; E.C. 2.3.1.43) that is associated with lower cardiovascular diseases risk. HDL cholesterol concentration and LCAT activity can be modulated by dietary fatty acids. Original data with substrate models have shown a positive effect of myristic acid (MA) on the esterification rate of cholesterol. The purpose of this study was to examine the effect of moderate intakes of MA associated with recommended intake of alpha‐linolenic acid (ALA) on LCAT activity in humans. Two experimental diets were tested for 3 months each. Diet 1‐MA 1.2% of total energy (TE) and ALA 0.9% TE, diet 2‐MA 1.8% and ALA 0.9% TE; a control diet (MA 1.2% and ALA 0.4% TE) was given 3 months before diet 1 and diet 2. The endogenous activity of LCAT was determined at completion of each diet. Compared with the control diet (13.2 ± 3.1 μmol CE/(L.h)), LCAT activity increased significantly (P < 0.001) with diet 1 (24.2 ± 3.6 μmol CE/(L.h)) and diet 2 (33.3 ± 7.4 μmol CE/(L.h)); the increase observed with diet 2 was significantly (P < 0.001) greater than that due to diet 1. These results suggest that ALA (from rapeseed oil, mainly in sn‐2 position) and MA (from dairy fat, mainly in sn‐2 position) favor LCAT activity, by respective increases of 83 and 38%. When they are supplied together, a complementary effect was observed (average increase of 152%). Moreover, these observations were associated with a decrease of the ratio of total to HDL‐cholesterol. In conclusion, our results suggest that moderate supply of MA (1.8% TE) associated with the recommended intake of ALA (0.9% TE) contributes to improve LCAT activity.
Improvement of insulin resistance after diet with a whole-grain based dietary product: results of a randomized, controlled cross-over study in obese subjects with elevated fasting blood glucose
Authors: Rave Klaus , Roggen Kerstin , Dellweg Sibylle , Heise Tim , tom Dieck Heike
Published: June 2007

Subjects with obesity and elevated fasting blood glucose are at high risk of developing type 2 diabetes which may be reduced by a dietary intervention leading to an improvement of insulin resistance. We investigated the potential of a whole-grain based dietary product (WG) with reduced starch content derived from double-fermented wheat during a hypo-energetic diet to positively influence body weight, fasting blood glucose, insulin resistance and lipids in comparison to a nutrient-dense meal replacement product (MR) in a randomized two-way cross-over study with two 4-week treatment periods separated by a 2-week wash-out. Subjects replaced at least two daily meals with WG and MR, respectively, targeting for a consumption of 200 g of either product per day. Total daily energy intake was limited to 7120 kJ. Thirty-one subjects (BMI 33·9 (sd 2·7) kg/m2, fasting blood glucose 6·3 (sd 0·8) mmol/l) completed the study. In both treatment groups body weight ( − 2·5 (sd 2·0) v. − 3·2 (sd 1·6) kg for WG v. MR), fasting blood glucose ( − 0·4 (sd 0·3) v. − 0·5 (sd 0·5) mmol/l), total cholesterol ( − 0·5 (sd 0·5) v. − 0·6 (sd 0·5) mmol/l), TAG ( − 0·3 (sd 0·9) v. − 0·3 (sd 1·2) mmol/l) and homeostasis model assessment (HOMA) insulin resistance score ( − 0·7 (sd 0·8) v. − 1·1 (sd 1·7) μU/ml ×  mmol/l) improved (P < 0·05) with no significant differences between the treatments. After statistical adjustment for the amount of body weight lost, however, the comparison between both groups revealed that fasting serum insulin (P = 0·031) and HOMA insulin resistance score (P = 0·049) improved better with WG than with MR. We conclude that WG favourably influences metabolic risk factors for type 2 diabetes independent from the amount of body weight lost during a hypo-energetic diet.
Protective effect of cyanidin 3-O-β-d-glucoside on ochratoxin A-mediated damage in the rat
Authors: Giacomo Claudia Di , Acquaviva Rosaria , Piva Andrea , Sorrenti Valeria , Vanella Luca , Piva Gianfranco , Casadei Gabriele , Fauci Luca La , Ritieni Alberto , Bognanno Matteo , Renzo Laura Di , Barcellona Maria L. , Morlacchini Mauro , Galvano Fabio
Published: June 2007

The aim of the present study was to verify whether the oral administration of cyanidin 3-O-β-d-glucoside (C3G) might counteract damage induced by chronic exposure (28 d) to ochratoxin A (OTA) in rats and if its effect may be mediated by haeme oxygenase-1 (HO-1). Forty male Sprague–Dawley rats, individually caged, were divided into four groups of ten animals. A control group received a commercial diet, group C3G received the control diet supplemented with C3G (1 g/kg feed), group OTA received the control diet supplemented with 200 parts per billion of OTA, and group OTA+C3G received the OTA group diet supplemented with C3G (1 g/kg feed). After 4 weeks of treatment animals were killed and the liver, kidneys and brain of each rat were collected and homogenised to evaluate non-proteic thiol groups (RSH), lipid hydroperoxide (LOOH) levels, HO-1 expression and DNA fragmentation. Rats of the OTA group showed a significant (P < 0·001) decrease in RSH content of kidney and liver and a significant (P < 0·001) increase of LOOH in all the examined tissues compared with the control group. In the OTA+C3G group both RSH content and LOOH levels were similar to those observed in the control group, demonstrating that C3G was able to counteract the effects of OTA. A significant (P < 0·001) induction of HO-1 was evident in kidney and liver of both OTA and C3G groups. DNA damage occurred in all the examined tissues of the OTA group, whereas C3G was able to prevent it. The present study confirmed that the effects of OTA are mediated by oxidative stress and demonstrated that C3G efficiently counteracted deleterious effects of OTA because of its antioxidant and HO-1-inducing properties.
What are the major correlates of macronutrient selection in Western populations?
Authors: de Castro John M.
Published: June 2007

In order to better understand the factors that may influence and regulate the intake of the macronutrients carbohydrate, fat and protein a 7 d diet diary technique was employed to study eating behaviour in the natural environment of free-living human subjects. In general, factors that promote energy intake tend to promote fat and protein intake to a greater extent than carbohydrate intake. This increased intake occurs as the result of: environmental factors such as social facilitation and the time of day, week or lunar phase; subjective factors such as hunger and elation; individual difference factors such as obesity, restraint and ageing. There are indications that the intake of macronutrients is regulated by negative feedback systems. In the short term, the amount of protein remaining in the stomach at the onset of a meal appears to have a restraining effect on intake, especially protein intake. Over several days, macronutrient intake appears to be affected by a nutrient-specific delayed negative feedback. Protein intake during 1 d is negatively associated with protein intake 2 and 3 d later, while carbohydrate intake is negatively related to later carbohydrate intake, and fat intake to later fat intake; both peaking after a 2 d delay. Studies of the intakes of twins suggested that many aspects of the control of macronutrient intake are influenced by inheritance; these factors include the overall amounts ingested, the before-meal stomach contents and the responsiveness of the subject to the negative impact of the stomach contents. The results indicate that macronutrient intakes are regulated by multiple persistent processes that are to a large extent inherited.
Conditioned food aversions: principles and practices, with special reference to social facilitation
Authors: Ralphs Michael H. , Provenza Frederick D.
Published: June 2007

Conditioned food aversion is a powerful experimental tool to modify animal diets. We have also investigated it as a potential management tool to prevent livestock from grazing poisonous plants such as tall larkspur (Delphinium barbeyi), white locoweed (Oxytropis sericea) and ponderosa pine (Pinus ponderosa) on western US rangelands. The following principles pertain to increasing the strength and longevity of aversions: mature animals retain aversions better than young animals; novelty of the plant is important, although aversions can be created to familiar plants; LiCl is the most effective emetic, and the optimum dose for cattle is 200 mg/kg body weight; averted animals should be grazed separately from non-averted animals to avoid the influence of social facilitation which can rapidly extinguish aversions. Social facilitation is the most important factor preventing widespread application of aversive conditioning. When averted animals see other animals eat the target food they will sample it, and if there is no adverse reaction they will continue eating and extinguish the aversion. However, if averted animals can be grazed separately, aversions will persist. Aversive conditioning may provide an effective management tool to prevent animals from eating palatable poisonous plants that cause major economic loss.
Immunonutrition and surgical practice
Authors: O'Flaherty Leán , Bouchier-Hayes David J.
Published: June 2007

Immunonutrition generally refers to the effect of the provision of specific nutrients on the immune system. These nutrients typically have immunoenhancing properties, and recent advances in nutrition support involve studies designed to exploit the desirable biological properties of these nutrients. The term immunonutrition strictly implies that we are focusing on the effect of certain nutrients on aspects of the immune system. However, in reality immunonutrition also refers to studies that not only examine the function of lymphocytes and leucocytes, but which also study the influence of key nutrients on the acute-phase response, the inflammatory response and on gastrointestinal structure and function. The interest, therefore, is on the impact of immunonutrition on all aspects of host defence mechanisms in response to a catabolic stress. Major surgery evokes an acute-phase response, a transient immunosuppression and alterations in gastrointestinal function. Normal function is usually restored after a few days; however, in a subgroup of patients homeostasis may be lost and development of the systemic inflammatory response syndrome (SIRS) ensues. Results of recent clinical trials suggest that provision of immunomodulatory nutrients, including glutamine, arginine,n-3 polyunsaturated fatty acids and dietary nucleotides, may promote restoration of normal tissue function post-operatively and prevent the occurrence of SIRS.
NMR of glycogen in exercise
Authors: Price Thomas B. , Rothman Douglas L. , Shulman Robert G.
Published: June 2007

Natural-abundance13CNMR spectroscopy is a non-invasive technique that enables in vivo assessments of muscle and/or liver glycogen concentrations. Over the last several years,13C NMR has been developed and used to obtain information about human glycogen metabolism with diet and exercise. Since NMR is non-invasive, more data points are available over a specified time course, dramatically improving the time resolution. This improved time resolution has enabled the documentation of subtleties of muscle glycogen re-synthesis following severe glycogen depletion that were not previously observed. Muscle and liver glycogen concentrations have been tracked in several different human populations under conditions that include: (1) muscle glycogen recovery from intense localized exercise with normal insulin and with insulin suppressed; (2) muscle glycogen recovery in an insulin-resistant population; (3) muscle glycogen depletion during prolonged low-intensity exercise; (4) effect of a mixed meal on postprandial muscle and liver glycogen synthesis. The present review focuses on basic13C NMR and gives results from selected studies.
Introduction toin vivo31P magnetic resonance spectroscopy of (human) skeletal muscle
Authors: Heerschap A. , Houtman C. , in 't Zandt H. J. A. , van den Bergh A. J. , Wieringa B.
Published: June 2007

31P magnetic resonance spectroscopy (MRS) offers a unique non-invasive window on energy metabolism in skeletal muscle, with possibilities for longitudinal studies and of obtaining important bioenergetic data continuously and with sufficient time resolution during muscle exercise. The present paper provides an introductory overview of the current status ofin vivo31P MRS of skeletal muscle, focusing on human applications, but with some illustrative examples from studies on transgenic mice. Topics which are described in the present paper are the information content of the31P magnetic resonance spectrum of skeletal muscle, some practical issues in the performance of this MRS methodology, related muscle biochemistry and the validity of interpreting results in terms of biochemical processes, the possibility of investigating reaction kineticsin vivoand some indications for fibre-type heterogeneity as seen in spectra obtained during exercise.
Arterio–venous differences to study macronutrient metabolism: introduction and overview
Authors: Macdonald I. A.
Published: June 2007

The arterio-venous difference technique is now well established in the study of organ and tissue metabolism. This technique requires samples to be obtained of the arterial blood supplying and the venous drainage from a tissue, together with a measurement of the blood flow through the tissue. The technique is most appropriate when the arterial concentration and tissue metabolism of a substance are constant, and when the blood flow is stable. If these criteria are not satisfied, care is needed in the interpretation of the results obtained. It should be recognized that the arterio-venous difference technique only measures the net exchange of a substance with the tissue, and that tracers are needed if unidirectional flux needs to be estimated. The other factors which must be borne in mind when intending to use this technique are the transit times of blood and the substance of interest through a tissue, the volume of distribution of the substance in the tissue, and the possibility that the venous samples obtained are derived from a mixture of different tissues.
Limb and skeletal muscle blood flow measurements at rest and during exercise in human subjects
Authors: Rådegran Göran
Published: June 2007

The aim of the present review is to present techniques used for measuring blood flow in human subjects and advice as to when they may be applicable. Since blood flow is required to estimate substrate fluxes, energy turnover and metabolic rate of skeletal muscle, accurate measurements of blood flow are of extreme importance. Several techniques have therefore been developed to enable estimates to be made of the arterial inflow to, venous outflow from, or local blood flow within the muscle. Regional measurements have been performed using electromagnetic flow meters, plethysmography, indicator methods (e.g. thermodilution and indo-cyanine green dye infusion), ultrasound Doppler, and magnetic resonance velocity imaging. Local estimates have been made using 133Xe clearance, microdialysis, near i.r. spectroscopy, positron emission tomography and laser Doppler. In principle, the aim of the study, the type of interventions and the limitations of each technique determine which method may be most appropriate. Ultrasound Doppler and continuous indo-cyanine green dye infusion gives the most accurate limb blood flow measurements at rest. Moreover, the ultrasound Doppler is unique, as it does not demand a steady-state, and because its high temporal resolution allows detection of normal physiological variations as well as continuous measurements during transitional states such as at onset of and in recovery from exercise. During steady-state exercise thermodilution can be used in addition to indo-cyanine green dye infusion and ultrasound Doppler, where the latter is restricted to exercise modes with a fixed vessel position. Magnetic resonance velocity imaging may in addition be used to determine blood flow within deep single vessels. Positron emission tomography seems to be the most promising tool for local skeletal muscle blood-flow measurements in relation to metabolic activity, although the mode and intensity of exercise will be restricted by the apparatus design.
Skeletal muscle substrate metabolism during exercise: methodological considerations
Authors: van Hall Gerrit , González-Alonso José , Sacchetti Massimo , Saltin Bengt
Published: June 2007

The aim of the present article is to evaluate critically the various methods employed in studies designed to quantify precisely skeletal muscle substrate utilization during exercise. In general, the pattern of substrate utilization during exercise can be described well from O2 uptake measurements and the respiratory exchange ratio. However, if the aim is to quantify limb or muscle metabolism, invasive measurements have to be carried out, such as the determination of blood flow, arterio-venous (a-v) difference measurements for O2 and relevant substrates, and biopsies of the active muscle. As many substrates and metabolites may be both taken up and released by muscle at rest and during exercise, isotopes can be used to determine uptake and/or release and also fractional uptake can be accounted for. Furthermore, the use of isotopes opens up further possibilities for the estimation of oxidation rates of various substrates. There are several methodological concerns to be aware of when studying the metabolic response to exercise in human subjects. These concerns include: (1) the muscle mass involved in the exercise is largely unknown (bicycle or treadmill). Moreover, whether the muscle sample obtained from a limb muscle and the substrate and metabolite concentrations are representative can be a problem; (2) the placement of the venous catheter can be critical, and it should be secured so that the blood sample represents blood from the active muscle with a minimum of contamination from other muscles and tissues; (3) the use of net limb glycerol release to estimate lipolysis is probably not valid (triacylglycerol utilization by muscle), since glycerol can be metabolized in skeletal muscle; (4) the precision of blood-borne substrate concentrations during exercise measured by a-v difference is hampered since they become very small due to the high blood flow. Recommendations are given in order to obtain more quantitative and conclusive data in studies investigating the regulatory mechanisms for substrate choice by muscle.
Microdialysis of skeletal muscle at rest
Authors: Henriksson Jan
Published: June 2007

Techniques in human skeletal muscle research are by necessity predominantly 'descriptive'.Microdialysis has raised high expectations that it could meet the demand for a method that allows 'mechanistic' investigations to be performed in human skeletal muscle. In the present review, some views are given on how well the initial expectations on the use of the microdialysis technique in skeletal muscle have been fulfilled, and the areas in which additional work is needed in order to validate microdialysis as an important metabolic technique in this tissue. The microdialysis catheter has been equated to an artificial blood vessel, which is introduced into the tissue. By means of this 'vessel' the concentrations of compounds in the interstitial space can be monitored. The concentration of substances in the collected samples is dependent on the rate of perfusate flow. When perfusate flow is slow enough to allow complete equilibration between interstitial and perfusate fluids, the concentration in the perfusate is maximal and identical to the interstitial concentration. Microdialysis data may be influenced by changes in blood flow, especially in instances where the tissue diffusivity limits the recovery in vivo, i.e. when recovery in vitro is 100 %, whereas the recovery in vivo is less than 100 %. Microdialysis data indicate that a significant arterial-interstitial glucose concentration gradient exists in skeletal muscle but not in adipose tissue at rest. While the concentrations of glucose and lactate in the dialysate from skeletal muscle are close to the expected values, the glycerol values obtained for muscle are still puzzling. Ethanol added to the perfusate will be cleared by the tissue at a rate that is determined by the nutritive blood flow (the microdialysis ethanol technique). It is concluded that microdialysis of skeletal muscle has become an important technique for mechanistic studies in human metabolism and nutrition.
Body composition, water turnover and energy turnover assessment with labelled water
Authors: Westerterp Klaas R.
Published: June 2007

Our understanding of human energy metabolism has benefited greatly from the application of water labelled with 2H and 18O for the measurement of total body water, water turnover and total daily energy expenditure. Applications include validation of techniques for the assessment of dietary intake and physical activity, assessment of water and energy requirement and the assessment of the effect of dietary and physical activity interventions, including its use with endurance athletes competing at the highest level. Critical aspects of the application are isotope dose preparation, sample collection, sample analysis and the calculation procedure. The labelled-water method can easily be applied in normal living conditions, including exercise, and in the clinical setting. However, sample analysis requires a sophisticated laboratory with an isotope-ratio mass spectrometer and a sample preparation system. Examples of insights based on labelled-water studies are: (1) self-reported dietary intakes often underestimate energy requirements; (2) subjects have problems maintaining energy balance when daily energy expenditure exceeds 2.5 times resting energy expenditure. Devices for the assessment of physical activity validated using labelled water allow the study of activity patterns and strategies to influence the activity level of a sedentary society.
Use of stable isotopes to study carbohydrate and fat metabolism at the whole-body level
Authors: Coggan Andrew R.
Published: June 2007

The present review discusses the advantages and limitations of using stable-isotope tracers to assess carbohydrate and fat metabolism at the whole-body level. One advantage of stable-(v. radioactive-) isotope tracers is the relative ease with which the location of a label within a molecule can be determined using selected-ion-monitoring GC-mass spectrometry (SIM-GC- MS). This technique minimizes potential problems due to label recycling, allows the use of multiple-labelled compounds simultaneously (e.g. to quantify glucose cycling), and perhaps most importantly, has led to the development of unique stable-isotope methods for, for example, quantifying gluconeogenesis. However, the limited sensitivity of SIM-GC-MS sometimes requires that relatively large amounts of a stable-isotope tracer be used, thus increasing cost and potentially altering metabolism. At least theoretically, stable- (or radioactive-) isotope tracers can also be used in conjunction with indirect calorimetry to estimate utilization of muscle glycogen or triacylglycerol stores, thus potentially circumventing the need to obtain muscle biopsies. These calculations, however, require certain critical assumptions, which if incorrect could lead to major errors in the values obtained. Despite such limitations, stable-isotope tracers provide a powerful and sometimes unique tool for investigating carbohydrate and fat metabolism at the whole-body level. With continuing advances in availability, instrumentation and methods, it is likely that stable-isotope tracers will become increasingly important in the immediate future.
Glycerol production and utilization measured using stable isotopes
Authors: Landau Bernard R.
Published: June 2007

The rate of appearance of glycerol in the systemic circulation is determined from the enrichment of arterial blood glycerol when labelled glycerol is infused intravenously. This value provides a good measure of whole-body lipolysis during fasting, except that arterial infusion and venous sampling, if feasible, would probably give a higher more-accurate value. Lipolysis occurs primarily in adipose tissue, although other tissues contribute, notably muscle. Measurement is based on the difference in the enrichment of the glycerol entering and leaving the tissue. Lipolysis is underestimated by the extent to which glycerol released by lipolysis does not enter the systemic circulation, as occurs when lipolysis takes place in the non-hepatic tissue of the splanchnic bed. Glycerol released into the systemic circulation is utilized mainly by liver, although kidney and muscle are also major users of glycerol. Measurement of glycerol utilization is based on the amount of labelled glycerol taken up by the tissues. Other tissues probably utilize glycerol to a smaller extent, but in total this represents a significant amount. Most glycerol taken up by liver is converted to glucose. Glucose is probably the major source of glycerol-3-phosphate used in the esterification of fatty acids by adipose tissue.
An overview of methods for assessment of free radical activity in biology
Authors: Jackson Malcolm J.
Published: June 2007

Assays which purport to assess free radical activity in biological systems are multiple. However, despite numerous published descriptions of new methods and modifications of methods to assess free radical activity in biological materials, there is still a lack of reliable techniques for quantification of activityin vivo. Analysis of a number of related indicators and use of a variety of approaches appears the only reliable way to evaluate these processesin vivo. In studies of free radical generation by contracting skeletal muscle we have attempted to use a variety of indicators, including measurement of endogenous antioxidant levels, measurement of indirect indicators of free radical activity (e.g. products of lipid peroxidation, DNA oxidation or protein oxidation) and, where possible, measurement of direct indicators of free radical activity by electron spin resonance techniques. In view of the relative lack of specificity of many available techniques, caution should be exerted in evaluating the numerous examples of isolated single measures of free radical activity which are present in the scientific literature.
Methods to detect DNA damage by free radicals: relation to exercise
Authors: Poulsen Henrik E. , Weimann Allan , Loft Steffen
Published: June 2007

Epidemiological investigations repeatedly show decreased morbidity from regular exercise compared with sedentary life. A large number of investigations have demonstrated increased oxidation of important cellular macromolecules, whereas other investigators have found no effects or even signs of lowering of oxidation of macromolecules. In particular, extreme and long-duration strenuous exercise appears to lead to deleterious oxidation of cellular macromolecules. The oxidation of DNA is important because the oxidative modifications of DNA bases, particularly the 8-hydroxylation of guanine, are mutagenic and have been implicated in a variety of diseases such as ageing and cancer. The methodologies for further investigation of the relationship between DNA oxidation and exercise are available. The preferred methods rely on HPLC or GC-mass spectrometry; whereas the theoretically-attractive liquid chromatography- tandem mass spectrometry is being developed. Caution should be taken to avoid artifacts because of the six orders of magnitude of difference between oxidized and non-oxidized DNA bases in tissues. The methods can be used to estimate tissue levels, i.e. a local concentration of oxidized DNA, or to estimate the rate of body DNA oxidation by the urinary output of repair products, the latter being a method that is independent of repair. During exercise there appears to be a shifting of dietary-dependent antioxidant, e.g. vitamin C and vitamin E, from muscle to plasma, and an increased oxidation in plasma of these antioxidants. Supplementation trials with antioxidants have not been able to increase exercise performance; however, optimum nutrition with antioxidants and possibly supplementation, could be important in the prevention of diseases in the long term. The pattern from these observations appears to be quite consistent; immediately after exercise, regardless of how intense, there do not appear to be any signs of oxidative damage to DNA. Acute or prolonged moderate exercise does not produce signs of oxidative DNA damage and might even be associated with lowering of the levels of oxidation of tissue DNA; however, after long-duration and intense exercise an increase in oxidative DNA modifications is apparent. We suggest as a hypothesis that the relationship between exercise and health is U-shaped. This hypothesis needs to be tested in detail in order to establish the maximum beneficial exercise level with regard to oxidative DNA modification, and also the level that could be deleterious and might even increase the risk for cancer and other diseases.
Analysis of cellular responses to free radicals: focus on exercise and skeletal muscle
Authors: Powers Scott K. , Lennon Shannon L.
Published: June 2007

Muscular exercise results in an increased production of radicals and other forms of reactive oxygen species (ROS). Recent evidence suggests that radicals and other ROS are an underlying aetiology in exercise-induced disturbances in muscle redox status. These exercise-induced redox disturbances in skeletal muscle are postulated to contribute to both muscle fatigue and/or exercise-induced muscle injury. To defend against ROS, muscle cells contain complex cellular defence mechanisms to reduce the risk of oxidative injury. Two major classes (enzymic and non-enzymic) of endogenous protective mechanisms work together to reduce the harmful effects of oxidants in the cell. Primary antioxidant enzymes include superoxide dismutase (EC1.15.1.1; SOD), GSH peroxidase (EC1.11.1.9; GPX), and catalase (EC1.11.1.6); these enzymes are responsible for removing superoxide radicals, H2O2and organic hydroperoxides, and H2O2respectively. Important non-enzymic antioxidants include vitamins E and C, β-carotene, GSH and ubiquinones. Vitamin E, β-carotene and ubiquinone are located in lipid regions of the cell, whereas GSH and vitamin C are in aqueous compartments of the cell. Regular endurance training promotes an increase in both total SOD and GPX activity in actively-recruited skeletal muscles. High-intensity exercise training has been shown to be generally superior to low-intensity exercise in the upregulation of muscle SOD and GPX activities. Also, training-induced upregulation of antioxidant enzymes is limited to highly-oxidative skeletal muscles. The effects of endurance training on non-enzymic antioxidants remain a relatively uninvestigated area.
Luminance-dependent hue shift in protanopes
Authors: BIMLER DAVID L. , PARAMEI GALINA V.
Published: June 2007

For normal trichromats, the hue of a light can change as its
luminance varies. This Bezold-Brücke (B-B) hue shift is commonly
attributed to nonlinearity in the blue–yellow opponent system. In
the present study, we questioned whether protanopes experience
analogous changes. Two protanopes (Ps) viewed spectral lights at six
luminance levels across three log steps. Two normal trichromats (NTs)
were tested for comparison. A variant of the color-naming method was
used, with an additional “white” term. To overcome the
difficulty of Ps' idiosyncratic color naming, we converted
color-naming functions into individual color spaces, by way of
interstimulus similarities and multidimensional scaling (MDS). The
color spaces describe each stimulus in terms of spatial coordinates, so
that hue shifts are measured geometrically, as displacements along
specific dimensions. For the NTs, a B-B shift derived through MDS
agreed well with values obtained directly by matching color-naming
functions. A change in color appearance was also observed for the Ps,
distinct from that in perceived brightness. This change was about twice
as large as the B-B shift for NTs and combined what the latter would
distinguish as hue and saturation shifts. The protanopic analogue of
the B-B shift indicates that the blue–yellow nonlinearity
persists in the absence of a red–green signal. In addition, at
mesopic levels (≤ 38 td), the Ps' MDS solution was two
dimensional at longer wavelengths, suggesting rod input. Conversely, at
higher luminance levels (76 td–760 td) the MDS solution was
essentially one dimensional, placing a lower limit on S-cone input at
longer wavelengths.
Brightness induction: Unequal spatial integration with increments
and decrements
Authors: HONG SANG WOOK , SHEVELL STEVEN K.
Published: June 2007

Modern theories of brightness induction include an influence from
regions that do not share a border with the target. This study tested
whether the spatial range of neural integration is the same with
incremental versus decremental contrast edges in relatively remote
parts of the background. Using an asymmetric matching task, observers
set the brightness of a comparison ring, within its own uniform
surround, to match the brightness of a test ring within a contiguous
surround and a noncontiguous background. The measurements showed that
the area of integration depended on the incremental versus decremental
contrast polarity at the edge between the surround and background. This
implies that brightness induction from an inhomogeneous background must
consider the polarity of contrast edges within the whole scene.
Flashing anomalous color contrast
Authors: PINNA BAINGIO , SPILLMANN LOTHAR , WERNER JOHN S.
Published: June 2007

A new visual phenomenon that we call flashing anomalous color
contrast is described. This phenomenon arises from the interaction
between a gray central disk and a chromatic annulus surrounded by black
radial lines. In an array of such figures, the central gray disk no
longer appears gray, but assumes a color complementary to that of the
surrounding annulus. The induced color appears: (1) vivid and
saturated; (2) self-luminous, not a surface property; (3) flashing with
eye or stimulus movement; (4) floating out of its confines; and (5)
stronger in extrafoveal than in foveal vision. The strength of the
effect depends on the number, length, width, and luminance contrast of
the radial lines. The results suggest that the chromatic ring bounding
the inner tips of the black radial lines induces simultaneous color
contrast, whereas the radial lines elicit, in conjunction with the gray
disk and the ring, the flashing, vividness, and high saturation of the
effect. The stimulus properties inducing the illusion suggest that
flashing anomalous color contrast may be based on asynchronous
interactions among multiple visual pathways.
Changes in color appearance caused by perceptual grouping
Authors: XIAN SHERRY X. , SHEVELL STEVEN K.
Published: June 2007

How is chromatic induction affected by perceptual grouping? Chromatic induction has been studied extensively, as has grouping, but only a small number of experiments have connected them. Even fewer reports go beyond weakly controlled qualitative observations. We report here a new and substantial color shift caused by perceptual grouping: a shift in appearance due to chromatic induction in one part of the visual field occurs also in a separate region that belongs to the same group. The color appearance of a test square within various surrounds was measured by asymmetric matching. The test square was at the center of an “hourglass” structure formed by other elements in the surround. The test shifted in color appearance toward the appearance of these other elements, whose color was affected by local chromatic induction. Control experiments ruled out as explanations (1) direct chromatic induction from the other elements into the test area, and (2) the influence of background light occluded by introducing the elements forming the hourglass.
Color constancy by asymmetric color matching with real objects in
three-dimensional scenes
Authors: de ALMEIDA VASCO M.N. , FIADEIRO PAULO T. , NASCIMENTO SÉRGIO M.C.
Published: June 2007

Color matching experiments use, in general, stimuli that are poor
representations of the natural world. The aim of this work was to
compare the degree of color constancy for a range of illuminant pairs
using a new matching technique that uses both real objects and
three-dimensional (3-D) real scenes. In the experiment, observers
viewed a 3-D real scene through a large beamsplitter that projects on
the right-hand side of the scene (match scene), the virtual image of a
3-D object (match object) such it appeared part of the scene. On the
left-hand side of the scene (test scene), observers viewed a
symmetrical scene containing a test object identical to the match
object. Test and match objects were both surrounded by the same
reflectances with identical spatial arrangement. The illuminant on the
test scene had always a correlated color temperature of 25,000 K. The
illuminant on the match scene could be any of seven different
illuminants with correlated color temperatures in the range 25,000
K–4000 K. In each trial, the observers, who were instructed to
perform surface color matches, adjusted the illuminant on the match
object. Constancy indices were very high (0.81–0.93), varied with
the color of the match object, and increased with the extent of the
illuminant change. Observer's mismatches, however, were
independent of the extent of the illuminant change.
Infant color vision: Influence of surround chromaticity on
spontaneous looking preferences
Authors: PEREVERZEVA MARIA , TELLER DAVIDA Y.
Published: June 2007

When infants are tested with stimuli of various chromaticities
embedded in a dark or achromatic (white) surround, they show maximal
preference for stimuli of maximal colorimetric purity, and minimal
preference for achromatic stimuli. We investigated how this pattern of
preferences changes with changes of surround chromaticity.
Sixteen-week-old infants were tested in two experimental conditions.
The surrounds in the first condition were red and white; and in the
second condition green and white. The three test stimuli varied in
colorimetric purity from white to red in the first condition, and from
white to green in the second condition. A test stimulus that appeared
achromatic to adults when viewed in the chromatic surround was
included. Infant spontaneous looking preferences changed with changes
of surround chromaticity. The changes were consistent with the
conclusion that infant looking behavior is governed by a preference for
the stimuli that differ maximally in purity from the surround. The
implications of this pattern of results are discussed.
Color and language: Worldwide distribution of Daltonism and
distinct words for “blue”
Authors: BROWN ANGELA M. , LINDSEY DELWIN T.
Published: June 2007

A geographical review of the published literature confirmed that
red–green color-vision deficiency (Daltonism) is rare near the
equator and more prevalent at higher latitudes, as others have
reported. A survey of dictionaries of the languages spoken by the
populations for which Daltonism data are available confirmed that
distinct words for “blue” are also rare near the equator,
and more common at higher latitudes. These results were compared to
show an even stronger relation between the proportion of languages with
a word for “blue” and the prevalence of Daltonism. We
believe that the strong correlation between “blue” and
Daltonism suggests that an evolutionary, physiological cause for both
phenomena.
Cone pigment polymorphism in New World monkeys: Are all pigments
created equal?
Authors: ROWE MICKEY P. , JACOBS GERALD H.
Published: June 2007

Most platyrrhine monkeys have a triallelic M/L opsin gene
polymorphism that underlies significant individual variations in color
vision. A survey of the frequencies of these polymorphic genes suggests
that the three alleles occur with equal frequency among squirrel
monkeys (subfamily Cebinae), but are not equally frequent in a number
of species from the subfamily Callitrichinae. This departure from equal
frequency in the Callitrichids should slightly increase the ratio of
dichromats to trichromats in the population and significantly alter the
relative representation of the three possible dichromatic and
trichromatic phenotypes. A particular feature of the inequality is that
it leads to a relative increase in the number of trichromats whose
M/L pigments have the largest possible spectral separation. To
assess whether these trichromatic phenotypes are equally well equipped
to make relevant visual discriminations, psychophysical experiments
were run on human observers. A technique involving the functional
substitution of photopigments was used to simulate the discrimination
between fruits among a background of leaves. The goal of the simulation
was to reproduce in the cones of human observers excitations equivalent
to those produced in monkey cones as the animals view fruit. Three
different viewing conditions were examined involving variations in the
relative luminances of fruit and leaves and the spectrum of the
illuminant. In all cases, performance was best for simulated
trichromacies including M/L pigments with the largest spectral
separation. Thus, the inequality of opsin gene frequency in
Callitrichid monkeys may reflect adaptive pressures.
Multidimensional scaling of D15 caps: Color-vision defects among tobacco smokers?
Authors: BIMLER DAVID , KIRKLAND JOHN
Published: June 2007

Tobacco smoke contains a range of toxins including carbon monoxide and cyanide. With specialized cells and high metabolic demands, the optic nerve and retina are vulnerable to toxic exposure. We examined the possible effects of smoking on color vision: specifically, whether smokers perceive a different pattern of suprathreshold color dissimilarities from nonsmokers. It is already known that smokers differ in threshold color discrimination, with elevated scores on the Roth 28-Hue Desaturated panel test. Groups of smokers and nonsmokers, matched for sex and age, followed a triadic procedure to compare dissimilarities among 32 pigmented stimuli (the caps of the saturated and desaturated versions of the D15 panel test). Multidimensional scaling was applied to quantify individual variations in the salience of the axes of color space. Despite the briefness, simplicity, and “low-tech” nature of the procedure, subtle but statistically significant differences did emerge: on average the smoking group were significantly less sensitive to red–green differences. This is consistent with some form of injury to the optic nerve.