Search PubMed⌕ Search

Biomedical subjects

W E Lands

Publications and source records attributed to W E Lands.

At least 19 recordsLinked to original sources
PubMed2003

Primary prevention in cardiovascular disease: moving out of the shadows of the truth about death.

AIM: This review identifies deficits in current educational efforts for the primary prevention of cardiovascular disease. DATA SYNTHESIS: Essential fatty acids in the foods we eat have a subtle but powerful influence on hundreds of different processes in the life and death of humans, understanding of which has been delayed by two attitudes in the biomedical community. One involves a bias towards expensive curative/treatment interventions that neglect prevention of initial nutritional causes of disease and death, and the other involves careless logic in interpreting evidence of causes of disease and death. Both attitudes interfere with translation of published science of essential fatty acids into effective prevention of cardiovascular deaths, a situation made worse by a widespread wish for simple descriptions of complex interactions in disease. Some clinical signs and risk factors may be only shadows of true causal factors. For example, attention to cholesterol ignored important evidence that nutritional imbalances in expenditure/intake of energy and in omega-3/omega-6 essential fatty acids cause cardiovascular disease. Balancing the few percentage of daily calories in omega-3/omega-6 nutrients is not a question of obesity or blood cholesterol. Effective prevention through education will require targeting the causal risk factors that are known beyond the shadow of a doubt, but seldom discussed by health professionals and the public. CONCLUSIONS: Death from coronary heart disease comes from acute ischemia and arrhythmia, often following long-term chronic inflammatory vascular damage that predisposes to acute fatal thrombosis and arrhythmia. The three processes involve excessive self-healing actions of natural n-6 autacoids (auto = self, akos = healing) produced from tissue essential fatty acids that come only from foods. Readily corrected nutritional imbalances in expenditure/intake of energy and in omega-3/omega-6 essential fatty acids are causal risk factors with plausible mechanisms contributing to fatal events which can be prevented.

Cardiovascular Diseases↗
PubMed1998

A review of alcohol clearance in humans.

The level of blood or brain alcohol is considered to influence alcohol ingestion by causing subjective perceptions or neural activations that are reinforcing or rewarding. Alcohol-dependent people may try to maintain some desired tissue level, drinking to replace the millimolar levels that were cleared from the blood by metabolism. The biomedical literature describes many approaches to understanding the role of blood alcohol levels in human physiology and behavior, and this review examines some of the published results. They include the general kinetics of intake and removal of beverage alcohol as well as the characteristics of many different catalysts that can interact with alcohol. Because ingested alcohol creates blood levels that are a 1000-fold greater than those normally experienced during abstinence, ethanol may impose itself as an alternate substrate for the many oxidoreductases that act physiologically on other endogenous alcohols. Many enzymes that can act on millimolar ethanol have been isolated, and their structural genes are sequenced. Unfortunately, the genetic sequence does not indicate the physiological material upon which the translated gene product may act. In a sense, the set of enzymes with catalytic sites occupied by millimolar ethanol during alcohol drinking might constructively be regarded as "orphan gene products" whose physiological role remains to be clarified. This review is designed to indicate some of what is known, what is not known, and what needs to be known to improve the interpretations regarding adaptations to beverage alcohol and the ability of millimolar levels of alcohol to diminish dysphoria. The dysphoria may be influenced by ethanol, by ethanol metabolites, or by altered metabolism of currently unspecified endogenous substrates. A major challenge is to evaluate the multiple alternative variables within a context that stimulates curiosity and encourages quantitative tests of the relative contribution of each variable to the overall physiology of an individual.

Alcohol Dehydrogenase↗
PubMed1995

Long-term fat intake and biomarkers.

The patterns of fatty acids maintained in human tissues reflect the dietary abundances of n-3 and n-6 fatty acids and the selectivities of the various lipid-metabolizing enzymes and transport systems in tissues. Similar selectivities for enzymes of mice, rats, and humans permit data from all three to be used in predicting average long-term tissue responses to different diets. The participation of the highly unsaturated fatty acids arachidonate (an n-6 acid) and eicosapentaenoate (an n-3 acid) in chronic pathophysiological events gives importance to predicting their tissue abundance. The average proportions in tissue phospholipids are hyperbolically related to dietary supplies of their precursors linoleate (18:2n-6) and linolenate (18:3n-3). In contrast, the precursors are maintained in tissue triacylglycerols in a linear relation to their average dietary supply.

Animals↗
PubMed1995

Alcohol and energy intake.

One hundred years of research about the metabolism of alcohol have provided many details, but some general aspects of the physiologic value of alcohol remain uncertain or inadequately proven. Results from epidemiologic studies appear to be in conflict with interpretations based on results from indirect calorimetric studies. The apparent inability of body mass index to be maintained in women when alcohol is consumed with food may indicate impaired metabolic processes that need to be better understood. Current evidence on the effects of alcohol are summarized to identify experimental approaches that may provide information needed to resolve the current contradictions.

Alcohol Oxidoreductases↗
PubMed1994

Interaction between peroxidase and cyclooxygenase activities in prostaglandin-endoperoxide synthase. Interpretation of reaction kinetics.

Prostaglandin-endoperoxide synthases have two distinct enzymatic activities in the biosynthesis of prostanoids: a peroxidase and a fatty acid oxygenase. Hydroperoxides, such as the cyclooxygenase reaction product, prostaglandin G2, act both as substrates for the synthase peroxidase and as obligatory initiators of the cyclooxygenase reaction itself. A mechanistic scheme was devised to describe the interactions between the two activities of the synthase. This mechanism was based on a heme-dependent peroxidase mechanism such as that observed with horseradish peroxidase and initiation of the cyclooxygenase reaction by intramolecular reaction with a peroxidase intermediate. Rate equations derived from the mechanism were numerically integrated by an interactive computer program that consolidated the diverse phenomena to provide quantitative predictions of the reaction kinetics of the synthase. The predictions agreed well with experimental observations of the purified ovine seminal vesicle enzyme under a wide variety of conditions, including inhibition by exogenous hydroperoxide scavenger and by cyanide, stimulation by exogenous hydroperoxide, and inhibition of eicosapentaenoic acid oxygenation under conditions where arachidonic acid reacts rapidly. The detailed analyses of reaction kinetics made possible with the computer simulation provide important insights into the interactions between the two catalytic activities of the synthase in the control of prostaglandin biosynthesis.

Cyanides↗
PubMed1992

Maintenance of lower proportions of (n - 6) eicosanoid precursors in phospholipids of human plasma in response to added dietary (n - 3) fatty acids.

Competition between the (n - 3) and (n - 6) types of highly unsaturated fatty acids can diminish the abundance of (n - 6) eicosanoid precursors in a tissue, which in turn can diminish the intensity of tissue responses that are mediated by (n - 6) eicosanoids. The mixture of 20- and 22-carbon highly unsaturated fatty acids maintained in the phospholipids of human plasma is related to the dietary intake of 18:2 (n - 6) and 18:3 (n - 3) by empirical hyperbolic equations in a manner very similar to the relationship reported for laboratory rats (Lands, W.E.M., Morris, A. and Libelt, B. (1990) Lipids 25, 505-516). Analytical results from volunteers ingesting self-selected diets showed an inter-individual variance for the proportion of (n - 6) eicosanoid precursors in the fatty acids of plasma phospholipids of about 5%, but the variance among multiple samples taken from the same individual throughout the day was less (about 3%), closer to the experimental variance of the analytical procedure (about 1%). The reproducibility of the results makes it likely that analysis of fatty-acid composition of plasma lipids from individuals will prove useful in estimating the diet-related tendency for severe thrombotic, arthritic or other disorders that are mediated by (n - 6) eicosanoids. Additional constants and terms were included in the equations to account for the effects of 20- and 22-carbon highly unsaturated (n - 3) fatty acids in the diet. A lower constant for the 20- and 22-carbon (n - 3) fatty acids compared to that for the 18-carbon (n - 3) fatty acid in decreasing the ability of dietary 18:2 (n - 6) to maintain 20:4 (n - 6) in tissue lipids confirmed the greater competitive effectiveness of the more highly unsaturated n - 3 fatty acids in the elongation/desaturation process. Also, a lower constant for direct incorporation of 20-carbon fatty acids of the n - 6 vs. the n - 3 type indicated a greater competitive effectiveness of 20:4 (n - 6) relative to 20:5 (n - 3) in reesterification after release from tissue lipids. The equations may be used in reverse to estimate the dietary intakes of the (n - 3) and (n - 6) fatty acids by using the composition of the fatty acids that had been maintained in plasma lipids.

Aged↗
PubMed1992

Biochemistry and physiology of n-3 fatty acids.

Considering the n-3 fatty acids to be partial agonists relative to n-6 fatty acids helps consolidate into a unified interpretation the many diverse reports and controversies on the actions of these two types of essential fatty acids. Some research reports illustrate the similarities between these two types and some emphasize the differences, leaving readers to evaluate the status of n-3 fatty acids from a viewpoint that is conceptually similar to regarding a glass of water as half empty or half full. Both n-3 and n-6 types of fatty acids must be obtained through the diet because they are not synthesized de novo by vertebrates. Both types can support important physiological and developmental processes, can form eicosanoids (prostaglandins, leukotrienes, lipoxins, etc.), can be esterified to and hydrolyzed from tissue glycerolipids, and can be metabolically elongated and desaturated to a variety of highly unsaturated fatty acids. However, some nonesterified n-6 acids are vigorously converted to potent n-6 eicosanoids that exert intense agonist actions at eicosanoid receptors, whereas the n-3 acids less vigorously form n-3 eicosanoids that often produce less intense (partial) actions. Because both types owe their presence in vertebrate tissues to dietary intake, important physiological consequences follow the inadvertent selection of different average daily dietary supplies of these two types of polyunsaturated fatty acids.

Animals↗
PubMed1991

Iodometric measurement of lipid hydroperoxides in human plasma.

Many assay techniques have been used to measure lipid hydroperoxides in plasma, including absorbance of conjugated dienes and reactivity with thiobarbituric acid. Because these measurements are not specific for lipid hydroperoxides, we modified an exisiting iodometric method to correct for interfering phenomena and to provide a more specific measurement of the lipid hydroperoxide content of plasma. To ensure reproducible extraction of hydroperoxides from the many possible forms in plasma, the plasma was treated to hydrolyze enzymatically cholesterol ester, triglycerides, and phospholipids, and the nonesterified fatty acid peroxides were then extracted with ethyl acetate. Extracted lipids were reacted with potassium iodide in acetic acid and methylene chloride, and the resulting triiodide ion (I3-) was measured spectrophotometrically. Correction for nonoxidizing chromophores was made after back-titration of the triiodide ion to iodide with sodium thiosulfate and other non-peroxide oxidants were estimated by their resistance to reduction with glutathione peroxidase. Recovery of added hydroperoxide standards provided routine validations of the procedure's efficiency. The method indicated that insignificant amounts of hydroperoxide may be in the less polar lipids, but the total amount of lipid hydroperoxide esterfied in the plasma lipids of apparently healthy humans may be as much as 4.0 +/- 1.7 microM.

Esterases↗
PubMed1991

Use of a voltage-responsive timer to quantitate hydroperoxides by the cyclooxygenase activation assay.

The importance of lipid hydroperoxides in the interpretations of physiological and pathological processes requires a valid and reliable microanalytical procedure. However, quantitation of the small amounts of lipid hydroperoxides in biological samples is often attempted with methods that have low sensitivity, low validity, and/or low reliability. The highly sensitive and specific enzymatic assay based upon cyclooxygenase activation has many complex kinetic features that have caused it to be cumbersome and unreliable. Analysis of the cyclooxygenase kinetics showed that a fixed percentage (20%) of full reaction accurately substituted for the measurements of the time required to reach optimal velocity. Consequently, a voltage-responsive timer can report endpoints that are dependent upon picomole amounts of lipid hydroperoxide. Additional features of the timer are described which make the hydroperoxide assay simpler, faster, more reliable, and easier to perform than the previous method while still retaining its sensitivity and specificity.

Animals↗