Showing papers by "Case Western Reserve University published in 1997"

Osteogenic differentiation of purified, culture‐expanded human mesenchymal stem cells in vitro

Abstract: Human bone marrow contains a population of cells capable of differentiating along multiple mesenchymal cell lineages. Recently, techniques for the purification and culture-expansion of these human marrow-derived Mesenchymal Stem Cells (MSCs) have been developed. The goals of the current study were to establish a reproducible system for the in vitro osteogenic differentiation of human MSCs, and to characterize the effect of changes in the microenvironment upon the process. MSCs derived from 2nd or 3rd passage were cultured for 16 days in various base media containing 1 to 1000 nM dexamethasone (Dex), 0.01 to 4 mM L-ascorbic acid-2-phosphate (AsAP) or 0.25 mM ascorbic acid, and 1 to 10 mM beta-glycerophosphate (beta GP). Optimal osteogenic differentiation, as determined by osteoblastic morphology, expression of alkaline phosphatase (APase), reactivity with anti-osteogenic cell surface monoclonal antibodies, modulation of osteocalcin mRNA production, and the formation of a mineralized extracellular matrix containing hydroxyapatite was achieved with DMEM base medium plus 100 nM Dex, 0.05 mM AsAP, and 10 mM beta GP. The formation of a continuously interconnected network of APase-positive cells and mineralized matrix supports the characterization of this progenitor population as homogeneous. While higher initial seeding densities did not affect cell number of APase activity, significantly more mineral was deposited in these cultures, suggesting that events which occur early in the differentiation process are linked to end-stage phenotypic expression. Furthermore, cultures allowed to concentrate their soluble products in the media produced more mineralized matrix, thereby implying a role for autocrine or paracrine factors synthesized by human MSCs undergoing osteoblastic lineage progression. This culture system is responsive to subtle manipulations including the basal nutrient medium, dose of physiologic supplements, cell seeding density, and volume of tissue culture medium. Cultured human MSCs provide a useful model for evaluating the multiple factors responsible for the step-wise progression of cells from undifferentiated precursors to secretory osteoblasts, and eventually terminally differentiated osteocytes.

Growth kinetics, self‐renewal, and the osteogenic potential of purified human mesenchymal stem cells during extensive subcultivation and following cryopreservation

Abstract: Recent studies have demonstrated the existence of a subset of cells in human bone marrow capable of differentiating along multiple mesenchymal lineages. Not only do these mesenchymal stem cells (MSCs) possess multilineage developmental potential, but they may be cultured ex vivo for many passages without overt expression of a differentiated phenotype. The goals of the current study were to determine the growth kinetics, self-renewing capacity and the osteogenic potential of purified MSCs during extensive subcultivation and following cryopreservation. Primary cultures of MSCs were established from normal iliac crest bone marrow aspirates, an aliquot was cryopreserved and thawed, and then both frozen and unfrozen populations were subcultivated in parallel for as many as 15 passages. Cells derived from each passage were assayed for their kinetics of growth and their osteogenic potential in response to an osteoinductive medium containing dexamethasone. Spindle-shaped human MSCs in primary culture exhibit a lag phase of growth, followed by a log phase, finally resulting in a growth plateau state. Passaged cultures proceed through the same stages, however, the rate of growth in log phase and the final number of cells after a fixed period in culture diminishes as a function of continued passaging. The average number of population doublings for marrow-derived adult human MSCs was determined to be 38 +/- 4, at which time the cells finally became very broad and flattened before degenerating. The osteogenic potential of cells was conserved throughout every passage as evidenced by the significant increase in APase activity and formation of mineralized nodular aggregates. Furthermore, the process of cryopreserving and thawing the cells had no effect on either their growth or osteogenic differentiation. Importantly, these studies demonstrate that replicative senescence of MSCs is not a state of terminal differentiation since these cells remain capable of progressing through the osteogenic lineage. The use of population doubling potential as a measure of biological age suggests that MSCs are intermediately between embryonic and adult tissues, and as such, may provide an in situ source for mesenchymal progenitor cells throughout an adult's lifetime.

Iron accumulation in Alzheimer disease is a source of redox-generated free radicals.

Abstract: Damage from free radicals has been demonstrated in susceptible neuronal populations in cases of Alzheimer disease. In this study, we investigated whether iron, a potent source of the highly reactive hydroxyl radical that is generated by the Fenton reaction with H2O2, might contribute to the source of radicals in Alzheimer disease. We found, using a modified histochemical technique that relies on the formation of mixed valence iron complexes, that redox-active iron is associated with the senile plaques and neurofibrillary tangles—the pathological hallmark lesions of this disease. This lesion-associated iron is able to participate in in situ oxidation and readily catalyzes an H2O2-dependent oxidation. Furthermore, removal of iron was completely effected using deferoxamine, after which iron could be rebound to the lesions. Characterization of the iron-binding site suggests that binding is dependent on available histidine residues and on protein conformation. Taken together, these findings indicate that iron accumulation could be an important contributor toward the oxidative damage of Alzheimer disease.

Widespread Peroxynitrite-Mediated Damage in Alzheimer’s Disease

Abstract: Increasing evidence suggests that oxidative damage to proteins and other macromolecules is a salient feature of the pathology of Alzheimer’s disease. Establishing the source of oxidants is key to understanding what role they play in the pathogenesis of Alzheimer’s disease, and one way to examine this issue is to determine which oxidants are involved in damage. In this study, we examine whether peroxynitrite, a powerful oxidant produced from the reaction of superoxide with nitric oxide, is involved in Alzheimer’s disease. Peroxynitrite is a source of hydroxyl radical-like reactivity, and it directly oxidizes proteins and other macromolecules with resultant carbonyl formation from side-chain and peptide-bond cleavage. Although carbonyl formation is a major oxidative modification induced by peroxynitrite, nitration of tyrosine residues is an indicator of peroxynitrite involvement. In brain tissue from cases of Alzheimer’s disease, we found increased protein nitration in neurons, including but certainly not restricted to those containing neurofibrillary tangles (NFTs). Conversely, nitrotyrosine was undetectable in the cerebral cortex of age-matched control brains. This distribution is essentially identical to that of free carbonyls. These findings provide strong evidence that peroxynitrite is involved in oxidative damage of Alzheimer’s disease. Moreover, the widespread occurrence of nitrotyrosine in neurons suggests that oxidative damage is not restricted to long-lived polymers such as NFTs, but instead reflects a generalized oxidative stress that is important in disease pathogenesis.

CpG oligodeoxynucleotides act as adjuvants that switch on T helper 1 (Th1) immunity.

Abstract: Synthetic oligodeoxynucleotides (ODN) that contain unmethylated CpG motifs (CpG ODN) induce macrophages to secrete IL-12, which induces interferon (IFN)-γ secretion by natural killer (NK) cells. Since these cytokines can induce T helper 1 (Th1) differentiation, we examined the effects of coadministered CpG ODN on the differentiation of Th responses to hen egg lysozyme (HEL). In both BALB/c (Th2-biased) and B10.D2 (Th1-biased) mice, immunization with HEL in incomplete Freund's adjuvant (IFA) resulted in Th2-dominated immune responses characterized by HEL-specific secretion of IL-5 but not IFN-γ. In contrast, immunization with IFA-HEL plus CpG ODN switched the immune response to a Th1-dominated cytokine pattern, with high levels of HEL-specific IFN-γ secretion and decreased HEL-specific IL-5 production. IFA-HEL plus CpG ODN also induced anti-HEL IgG2a (a Th1-associated isotype), which was not induced by IFA-HEL alone. Control non–CpG ODN did not induce IFN-γ or IgG2a, excepting lesser increases in B10.D2 (Th1-biased) mice. Thus, CpG ODN provide a signal to switch on Th1-dominated responses to coadministered antigen and are potential adjuvants for human vaccines to elicit protective Th1 immunity.

Variations on a theme : cataloging human dna sequence variation

Abstract: New methods for the discovery and scoring of single-nucleotide polymorphisms (SNPs) offer the potential for considerably improved methods for genetic analysis of complex biological phenomena, particularly common diseases. In this Policy Forum, the authors call for a publicly supported effort to discover a large number of SNPs and to place the information in public databases. Participation in this public effort by the private sector would be particularly desirable.

The Sleep Heart Health Study: design, rationale, and methods.

Abstract: The Sleep Heart Health Study (SHHS) is a prospective cohort study designed to investigate obstructive sleep apnea (OSA) and other sleep-disordered breathing (SDB) as risk factors for the development of cardiovascular disease. The study is designed to enroll 6,600 adult participants aged 40 years and older who will undergo a home polysomnogram to assess the presence of OSA and other SDB. Participants in SHHS have been recruited from cohort studies in progress. Therefore, SHHS adds the assessment of OSA to the protocols of these studies and will use already collected data on the principal risk factors for cardiovascular disease as well as follow-up and outcome information pertaining to cardiovascular disease. Parent cohort studies and recruitment targets for these cohorts are the following: Atherosclerosis Risk in Communities Study (1,750 participants), Cardiovascular Health Study (1,350 participants), Framingham Heart Study (1,000 participants), Strong Heart Study (600 participants), New York Hypertension Cohorts (1,000 participants), and Tucson Epidemiologic Study of Airways Obstructive Diseases and the Health and Environment Study (900 participants). As part of the parent study follow-up procedures, participants will be surveyed at periodic intervals for the incidence and recurrence of cardiovascular disease events. The study provides sufficient statistical power for assessing OSA and other SDB as risk factors for major cardiovascular events, including myocardial infarction and stroke.

Relevance: a review of and a framework for the thinking on the notion in information science

Abstract: Information science emerged as the third subject, along with logic and philosophy, to deal with relevance-an elusive, human notion. The concern with relevance, as a key notion in information science, is traced to the problems of scientific communication. Relevance is considered as a measure of the effectiveness of a contact between a source and a destination in a communication process. The different views of relevance that emerged are interpreted and related within a framework of communication of knowledge. Different views arose because relevance was considered at a number of different points in the process of knowledge communication. It is suggested that there exists an interlocking, interplaying cycle of various systems of relevances.

Regeneration of adult axons in white matter tracts of the central nervous system

Abstract: It is widely accepted that the adult mammalian central nervous system (CNS) is unable to regenerate axons1. In addition to physical or molecular barriers presented by glial scarring at the lesion site2,3,4, it has been suggested that the normal myelinated CNS environment contains potent growth inhibitors5,6 or lacks growth-promoting molecules1,7. Here we investigate whether adult CNS white matter can support long-distance regeneration of adult axons in the absence of glial scarring, by using a microtransplantation technique8 that minimizes scarring9 to inject minute volumes of dissociated adult rat dorsal root ganglia directly into adult rat CNS pathways. This atraumatic injection procedure allowed considerable numbers of regenerating adult axons immediate access to the host glial terrain, where we found that they rapidly extended for long distances in white matter, eventually invading grey matter. Abortive regeneration correlated precisely with increased levels of proteoglycans within the extracellular matrix at the transplant interface, whereas successfully regenerating transplants were associated with minimal upregulation of these molecules. Our results demonstrate, to our knowledge for the first time, that reactive glial extracellular matrix at the lesion site is directly associated with failure of axon regrowth in vivo, and that adult myelinated white matter tracts beyond the glial scar can be highly permissive for regeneration.

An Instrument to Measure Functional Status Outcomes for Disorders of Excessive Sleepiness

Abstract: This article reports the development of the functional outcomes of sleep questionnaire (FOSQ). This is the first self-report measure designed to assess the impact of disorders of excessive sleepiness (DOES) on multiple activities of everyday living. Three samples were used in the development and psychometric analyses of the FOSQ: Sample 1 (n = 153) consisted of individuals seeking medical attention for a sleep problem and persons of similar age and gender having no sleep disorder; samples 2 (n = 24) and 3 (n = 51) were composed of patients from two medical centers diagnosed with obstructive sleep apnea (OSA). Factor analysis of the FOSQ yielded five factors: activity level, vigilance, intimacy and sexual relationships, general productivity, and social outcome. Internal reliability was excellent for both the subscales (alpha = 0.86 to alpha = 0.91) and the total scale (alpha = 0.95). Test-retest reliability of the FOSQ yielded coefficients ranging from r = 0.81 to r = 0.90 for the five subscales and r = 0.90 for the total measure. The FOSQ successfully discriminated between normal subjects and those seeking medical attention for a sleep problem (T157 = -5.88, p = 0.0001). This psychometric evaluation of the FOSQ demonstrated parameters acceptable for its application in research and in clinical practice to measure functional status outcomes for persons with DOES. Thus, the FOSQ can be used to determine how disorders of excessive sleepiness affect patients' abilities to conduct normal activities and the extent to which these abilities are improved by effective treatment of DOES.

Green Tea Constituent Epigallocatechin-3-Gallate and Induction of Apoptosis and Cell Cycle Arrest in Human Carcinoma Cells

Abstract: Background and Purpose: The polyphenolic compounds present in green tea show cancer chemopreventive effects in many animal tumor models. Epidemiologic studies have also suggested that green tea consumption might be effective in the prevention of certain human cancers. We investigated the effect of green tea polyphenols and the major constituent, epigallocatechin-3-gallate, on the induction of apoptosis (programmed cell death) and regulation of cell cycle in human and mouse carcinoma cells. Methods: Human epidermoid carcinoma cells (cell line A431), human carcinoma keratinocyte (cell line HaCaT), human prostate carcinoma cells (cell line DU145), mouse lymphoma cells (cell line L5178Y), and normal human epidermal keratinocytes (NHEKs) were used. Apoptosis was assessed by 1) the formation of internucleosomal DNA fragments by agarose gel electrophoresis, 2) confocal microscopy, and 3) flow cytometry after tagging the DNA fragments by fluorescence label. The distribution of cells in different phases of the cell cycle was analyzed by flow cytometry. Results: Treatment of A431 cells with green tea polyphenols and its components, epigallocatechin-3-gallate, epigallocatechin, and epicatechin-3-gallate, resulted in the formation of internucleo-somal DNA fragments, characteristic of apoptosis. Treatment with epigallocatechin-3-gallate also resulted in apoptosis in HaCaT, L5178Y, and DU145 cells, but not in NHEK. Confocal microscopy and flow cytometry confirmed the findings. The DNA cell cycle analysis showed that in A431 cells, epigallocatechin-3-gallate treatment resulted in arrest in the G 0 -G 1 phase of the cell cycle and a dose-dependent apoptosis. Conclusions: Green tea may protect against cancer by causing cell cycle arrest and inducing apoptosis. It needs to be evaluated in human trials.

Writing narrative literature reviews.

Abstract: Narrative literature reviews serve a vital scientific function, but few resources help people learn to write them. As compared with empirical reports, literature reviews can tackle broader and more abstract questions, can engage in more post hoc theorizing without the danger of capitalizing on chance, can make a stronger case for a null-hypothesis conclusion, and can appreciate and use methodological diversity better. Also, literature reviews can draw any of 4 conclusions: The hypothesis is correct, it has not been conclusively established but is the currently best guess, it is false, or the evidence permits no conclusion. Common mistakes of authors of literature review manuscripts are described. Narrative literature reviews form a vital part of most empirical articles, theses, and grant proposals, and of course many articles and book chapters are devoted specifically to reviewing the literature on a particular topic. Literature reviews serve a scientific field by providing a much-needed bridge between the vast and scattered assortment of articles on a topic and the reader who does not have time or resources to track them down. Reviews also present conclusions of a scope and theoretical level that individual empirical reports cannot normally address. For individual researchers, writing a major literature review article is a very infrequent but often a very important career contribution. Yet, despite the importance of narrative literature reviews, no easy and available way to learn to write them is known. Research methods textbooks do not usually explain how to do them, even though reviewing literature is an important research method. Most graduate seminars in research methods likewise devote little or no time to them. Apprenticeship with an accomplished literature reviewer seems to be one possible strategy to learn this technique, but such specialists are rare, and moreover it is generally considered more important for stu

Regulation of phosphoenolpyruvate carboxykinase (gtp) gene expression

Abstract: Phosphoenolpyruvate carboxykinase (GTP) (EC 4.1.1.32) (PEPCK) is a key enzyme in the synthesis of glucose in the liver and kidney and of glyceride-glycerol in white adipose tissue and the small intestine. The gene for the cytosolic form of PEPCK (PEPCK-C) is acutely regulated by a variety of dietary and hormonal signals, which result in alteration of synthesis of the enzyme. Major factors that increase PEPCK-C gene expression include cyclic AMP, glucocorticoids, and thyroid hormone, whereas insulin inhibits this process. PEPCK-C is absent in fetal liver but appears at birth, concomitant with the capacity for gluconeogenesis. Regulatory elements that control transcription of the PEPCK-C gene in liver, kidney, and adipose tissue have been delineated, and many of the transcription factors that bind to these elements have been identified. Transgenic mice have been especially useful in elucidating the physiological roles of specific sequence elements in the PEPCK-C gene promoter and in demonstrating the key role played at these sites by the isoforms of CAAT/enhancer binding protein in patterning of PEPCK-C gene expression during the perinatal period. The PEPCK-C gene provides a model for the metabolic control of gene transcription.

Longitudinal Study of Procrastination, Performance, Stress, and Health: The Costs and Benefits of Dawdling

Abstract: Procrastination is variously described as harmful, innocuous, or even beneficial. Two longitudinal studies examined procrastination among students. Procrastinators reported lower stress and less illness than nonprocrastinators early in the semester, but they reported higher stress and more illness late in the term, and overall they were sicker. Procrastinators also received lower grades on all assignments. Procrastination thus appears to be a self-defeating behavior pattern marked by short-term benefits and long-term costs.

Purification and cDNA cloning of the AdoMet-binding subunit of the human mRNA (N6-adenosine)-methyltransferase.

Abstract: The methylation of internal adenosine residues in eukaryotic mRNA, forming N6-methyladenosine (m6A), is catalyzed by a complex multicomponent enzyme. Previous studies suggested that m6A affects the efficiency of mRNA processing or transport, although the mechanism by which this occurs is not known. As a step toward better understanding the mechanism and function of this ubiquitous posttranscriptional modification, we have shown that HeLa mRNA (N6-adenosine)-methyltransferase requires at least two separate protein factors, MT-A and MT-B, and MT-A contains the AdoMet binding site on a 70-kDa subunit (MT-A70). MT-A70 was purified by conventional chromatography and electrophoresis, and was microsequenced. The peptide sequence was used to design a degenerate oligodeoxynucleotide that in turn was used to isolate the cDNA clone coding for MT-A70 from a HeLa cDNA library. Recombinant MT-A70 was expressed as a fusion protein in bacteria and was used to generate anti-MT-A70 antisera in rabbits. These antisera recognize MT-A70 in HeLa nuclear extracts by western blot and are capable of depleting (N6-adenosine)-methyltransferase activity from HeLa nuclear extract, confirming that MT-A70 is a critical subunit of (N6-adenosine)-methyltransferase. Northern blot analysis reveals that MT-A70 mRNA is present in a wide variety of human tissues and may undergo alternative splicing. MT-A70 cDNA probe hybridizes to a 2.0-kilobase (kb) polyadenylated RNA isolated from HeLa cells, whereas it hybridizes to two predominant RNA species (approximately 2.0 kb and 3.0 kb) using mRNA isolated from six different human tissues. Analysis of the cDNA sequence indicates that it codes for a 580-amino acid protein with a predicted MW = 65 kDa. The predicted protein contains sequences similar to consensus methylation motifs I and II identified in prokaryotic DNA (N6-adenosine)-methyltransferases, suggesting the functional conservation of peptide motifs. MT-A70 also contains a long region of homology to the yeast protein SPO8, which is involved in induction of sporulation by an unknown mechanism.

Formation of de novo centromeres and construction of first-generation human artificial microchromosomes.

Abstract: We have combined long synthetic arrays of alpha satellite DNA with telomeric DNA and genomic DNA to generate artificial chromosomes in human HT1080 cells. The resulting linear microchromosomes contain exogenous alpha satellite DNA, are mitotically and cytogenetically stable in the absence of selection for up to six months in culture, bind centromere proteins specific for active centromeres, and are estimated to be 6–10 megabases in size, approximately one-fifth to one-tenth the size of endogenous human chromosomes. We conclude that this strategy results in the formation of de novo centromere activity and that the microchromosomes so generated contain all of the sequence elements required for stable mitotic chromosome segregation and maintenance. This first-generation system for the construction of human artificial chromosomes should be suitable for dissecting the sequence requirements of human centromeres, as well as developing constructs useful for therapeutic applications.

Ionic Mechanisms of Propagation in Cardiac Tissue Roles of the Sodium and L-type Calcium Currents During Reduced Excitability and Decreased Gap Junction Coupling

Abstract: In cardiac tissue, reduced membrane excitability and reduced gap junction coupling both slow conduction velocity of the action potential. However, the ionic mechanisms of slow conduction for the two conditions are very different. We explored, using a multicellular theoretical fiber, the ionic mechanisms and functional role of the fast sodium current, INa, and the L-type calcium current, ICa(L), during conduction slowing for the two fiber conditions. A safety factor for conduction (SF) was formulated and computed for each condition. Reduced excitability caused a lower SF as conduction velocity decreased. In contrast, reduced gap junction coupling caused a paradoxical increase in SF as conduction velocity decreased. The opposite effect of the two conditions on SF was reflected in the minimum attainable conduction velocity before failure: decreased excitability could reduce velocity to only one third of control (from 54 to 17 cm/s) before failure occurred, whereas decreased coupling could reduce velocity to as low as 0.26 cm/s before block. Under normal conditions and conditions of reduced excitability, ICa(L) had a minimal effect on SF and on conduction. However, ICa(L) played a major role in sustaining conduction when intercellular coupling was reduced. This phenomenon demonstrates that structural, nonmembrane factors can cause a switch of intrinsic membrane processes that support conduction. High intracellular calcium concentration, [Ca]i, lowered propagation safety and caused earlier block when intercellular coupling was reduced. [Ca]i affected conduction via calcium-dependent inactivation of ICa(L). The increase of safety factor during reduced coupling suggests a major involvement of uncoupling in stable slow conduction in infarcted myocardium, making microreentry possible. Reliance on ICa(L) for this type of conduction suggests ICa(L) as a possible target for antiarrhythmic drug therapy.

In vivo bidirectional color Doppler flow imaging of picoliter blood volumes using optical coherence tomography.

Abstract: We describe a novel optical system for bidirectional color Doppler imaging of flow in biological tissues with micrometer-scale resolution and demonstrate its use for in vivo imaging of blood flow in an animal model. Our technique, color Doppler optical coherence tomography (CDOCT), performs spatially localized optical Doppler velocimetry by use of scanning low-coherence interferometry. CDOCT is an extension of optical coherence tomography (OCT), employing coherent signal-acquisition electronics and joint time-frequency analysis algorithms to perform flow imaging simultaneous with conventional OCT imaging. Cross-sectional maps of blood flow velocity with <50-µm spatial resolution and <0.6-mm/s velocity precision were obtained through intact skin in living hamster subdermal tissue. This technology has several potential medical applications.

Social Ostracism by Coworkers: Does Rejection Lead to Loafing or Compensation?

Abstract: A new theoretical model and research paradigm are introduced to investigate the phenomenon of social ostracism-being ignored by others who are in one's presence. The authors examined the effects of social ostracism on individuals' subsequent contributions to a group task. Social loafing Optically occurs on collective tasks. However; to regain their sense of belonging to the group, the authors expected ostracized individuals to socially compensate-to work harder collectively than coactively. Participants were asked to generate as many uses as they could for an object, either coactively or collectively with two others who had either ostracized or included them in an earlier ball-tossing exchange. Ostracized females socially compensated, whereas nonostracized females neither loafed nor compensated. Ostracized and nonostracized males socially loafed. Based on these data and the accompanying attributional and nonverbal analyses, the authors surmised that males and females interpret and respond to social ostrac...

Development of cognitive instruments for use in clinical trials of antidementia drugs: Additions to the Alzheimer's Disease Assessment Scale that broaden its scope.

Abstract: SummaryThe cognitive assessment protocol of the Alzheimer's Disease Cooperative Study (ADCS) was designed to evaluate the reliability and validity of cognitive assessment measures that might be valuable additions to the Alzheimer's Disease Assessment Scale (ADAS) or other concise batteries used in a

Regulation of myocardial carbohydrate metabolism under normal and ischaemic conditions. Potential for pharmacological interventions

Abstract: Time for primary review 28 days. The regulation of mammalian myocardial carbohydrate metabolism is complex in that it is linked to arterial substrate and hormone levels, coronary flow, inotropic state and the nutritional status of the tissue. Optimal cardiac function under normal and pathological conditions is dependent upon glycolysis and pyruvate oxidation. The purpose of this review is to examine the regulation of myocardial carbohydrate metabolism under physiological conditions, and during myocardial ischaemia and reperfusion. The therapeutic potential of a variety of pharmacological interventions affecting myocardial carbohydrate metabolism will then be discussed. The tricarboxylic acid cycle (TCA cycle) provides reducing equivalents for mitochondrial oxidative phosphorylation, resulting in the condensation of ADP and inorganic phosphate to regenerate ATP, and is fueled by acetyl-CoA formed primarily from oxidation of pyruvate and fatty acids (Fig. 1). Cardiomyocytes oxidise fatty acids derived from both the plasma and the breakdown of intracellular triacylglycerol stores, while pyruvate is derived from either lactate dehydrogenase or glycolysis. The rates of these metabolic pathways are tightly coupled to the rate of contractile work, and conversely, contractile work is coupled to the supply of oxygen and the rate of oxidative phosphorylation (Fig. 1). Early studies in animals [1] and human [2, 3] showed that after an overnight fast the heart extracts free fatty acids (FFA), lactate and glucose from the blood, and that if one assumes complete oxidation of extracted substrates, fatty acids are the major oxidative fuel for the heart (60–100% of the oxygen consumption), with a lesser contribution from lactate and glucose (0–20% from each) [2, 3]. Subsequent studies by others using a variety of experimental approaches have confirmed these early results (see [4–7] for reviews). Fig. 1 Schematic depiction of myocardial substrate metabolism. Abbreviations: G 6-P, glucose 6-phosphate; TCA, tricarboxylic acid; GT, GLUT 1 and GLUT 4 glucose …

The Measurement of Age, Age Structuring, and the Life Course

Abstract: The measurement of age, age structuring, and the life course has become more problematic as the study of human lives has moved toward more detailed analyses and explanations. As we seek to better understand the course of human lives in contemporary and changing societies, the effective empirical measurement of its key concepts simultaneously becomes more pressing and more complicated. We first review the critical concepts of, and measurement strategies associated with, age and age structuring—including a discussion of different types of age, subjective age identification, age norms and age expectations, critical life events, life phases, and life review. We then discuss state-of-the-art methods for measuring the life course, especially through life history and event matrices, and we close the chapter with some comments on the organization, analysis, and modeling of data.

Racial differences in sleep-disordered breathing in African-Americans and Caucasians.

Abstract: In this case-control family study of sleep-disordered breathing (SDB), we describe the distributions of SDB and SDB risk factors in African-Americans and Caucasians. A total of 225 African-Americans and 622 Caucasians, ages 2 to 86 yr, recruited as members of families with an individual with known sleep apnea (85 index families) or as members of neighborhood control families (63 families) were studied with an overnight home sleep-study, questionnaires, and physical measurements. A subsample underwent cephalometry. Outcome measures were the respiratory disturbance index (RDI) and a binary variable indicating the presence of increased apneic activity (IAA). In both races, a strong relationship was demonstrated between the (log transformed) RDI and age and age2. African-Americans with SDB were younger than Caucasians with SDB (37.2 +/- 19.5 versus 45.6 +/- 18.7 yr, p < 0.01). In subjects < or = 25 yr, RDI level and IAA prevalence were higher in African-Americans (odds ratio, adjusted for obesity, sex, proban...

Improved Discriminative and Evaluative Capability of a Refined Version of Skindex, a Quality-of-Life Instrument for Patients With Skin Diseases

Abstract: Objective: To improve Skindex, a dermatologic quality-of-life instrument. Design: Cross-sectional and longitudinal questionnaire study. Setting: Dermatology clinic of a Veterans Affairs hospital and private dermatology practices. Patients: Patients waiting for dermatology appointments; 201 patients responded to the original version of Skindex and 692 additional patients to the revised version. Main Outcome Measures: Reproducibility, internal consistency reliability, and validity of the revised version of Skindex. The revised version was compared with the original in 3 ways: the amount of time patients need to complete it; discriminative capability , determined as the number of items to which patients chose the same response; and evaluative capability , determined as the number of scales that were responsive to patients' reports of clinical change. Results: With the revised 29-item version of Skindex, scale scores were reproducible after 72 hours (r=0.88-0.92) and were internally reliable (Cronbach α=0.87-0.96). The instrument demonstrated both construct and content validity: patients with psoriasis and eczema responded with higher scores than those with isolated lesions; in an exploratory principal axes factor analysis with an oblique rotation, 97% of the common variance was explained by 3 factors that correlated with the a priori scales; and most patients' responses to an open-ended question about their skin disease were addressed by items in the instrument. The average time to complete the revised instrument was 5 minutes (compared with 15 minutes for the original version). For only 3 items (10%) did 70% or more of patients choose the same response (vs 17 [28%] of items in the original version). All scales changed significantly in the expected direction in patients who reported that their skin had changed after 3 months (vs only 3 of 8 scales originally). Conclusion: The 29-item version of Skindex remains reliable and valid, but has decreased respondent burden and improved discriminative and evaluative capability. Arch Dermatol. 1997;133:1433-1440