Showing papers by "University of Connecticut published in 1997"

Respondent-driven sampling : A new approach to the study of hidden populations

Abstract: A population is “hidden” when no sampling frame exists and public acknowledgment of membership in the population is potentially threatening. Accessing such populations is difficult because standard probability sampling methods produce low response rates and responses that lack candor. Existing procedures for sampling these populations, including snowball and other chain-referral samples, the key-informant approach, and targeted sampling, introduce well-documented biases into their samples. This paper introduces a new variant of chain-referral sampling, respondent-driven sampling, that employs a dual system of structured incentives to overcome some of the deficiencies of such samples. A theoretic analysis, drawing on both Markov-chain theory and the theory of biased networks, shows that this procedure can reduce the biases generally associated with chain-referral methods. The analysis includes a proof showing that even though sampling begins with an arbitrarily chosen set of initial subjects, as do most chain-referral samples, the composition of the ultimate sample is wholly independent of those initial subjects. The analysis also includes a theoretic specification of the conditions under which the procedure yields unbiased samples. Empirical results, based on surveys of 277 active drug injectors in Connecticut, support these conclusions. Finally, the conclusion discusses how respondent- driven sampling can improve both network sampling and ethnographic 44 investigation.

Comfortable and maximum walking speed of adults aged 20—79 years: reference values and determinants

Abstract: Objectives: to establish reference values for both comfortable and maximum gait speed and to describe the reliability of the gait speed measures and the correlation of selected variables with them. Design: descriptive and cross-sectional. Methods: subjects were 230 healthy volunteers. Gait was timed over a 7.62 m expanse of floor. Actual and height normalized speed were determined. Lower extremity muscle strength was measured with a hand-held dynamometer. Results: mean comfortable gait speed ranged from 127.2 cm/s for women in their seventies to 146.2 cm/s for men in their forties. Mean maximum gait speed ranged from 174.9 cm/s for women in their seventies to 253-3 cm/s for men in their twenties. Both gait speed measures were reliable (coefficients > 0.903) and correlated significantly with age (r^ — 0.210), height (r^ 0.220) and the strengths of four measured lower extremity muscle actions (r = 0.190-0.500). The muscle action strengths most strongly correlated with gait speed were nondominant hip abduction (comfortable speed) and knee extension (maximum speed). Conclusions: these normative values should give clinicians a reference against which patient performance can be compared in a variety of settings. Gait speed can be expected to be reduced in individuals of greater age and of lesser height and lower extremity muscle strength.

Behavioral phenotypes of inbred mouse strains: implications and recommendations for molecular studies.

Abstract: Choosing the best genetic strains of mice for developing a new knockout or transgenic mouse requires extensive knowledge of the endogenous traits of inbred strains. Background genes from the parental strains may interact with the mutated gene, in a manner which could severely compromise the interpretation of the mutant phenotype. The present overview summarizes the literature on a wide variety of behavioral traits for the 129, C57BL/6, DBA/2, and many other inbred strains of mice. Strain distributions are described for open field activity, learning and memory tasks, aggression, sexual and parental behaviors, acoustic startle and prepulse inhibition, and the behavioral actions of ethanol, nicotine, cocaine, opiates, antipsychotics, and anxiolytics. Using the referenced information, molecular geneticists can choose optimal parental strains of mice, and perhaps develop new embryonic stem cell progenitors, for new knockouts and transgenics to investigate gene function, and to serve as animal models in the development of novel therapeutics for human genetic diseases.

The Impact of Natural Culture and Economic Ideology on Managerial Work Values: A Study of the United States, Russia, Japan, and China

Abstract: This study assesses the impact of economic ideology and national culture on the individual work values of managers in the United States, Russia, Japan, and China. The convergence-divergence-crossvergence (CDC) framework was used as theoretical framework for the study, while the Schwartz Value Survey (SVS) was used to operationalize over investigation of managerial work values across these four countries. The findings largely support the crossvergence prospective, while also confirming the role of national culture. Implications from the findings are drawn for the convergence-divergence-crossvergence of values, as well as for the feasibility of multidomestic or global strategies for a corporate culture.

Functional Role of High-Affinity Anandamide Transport, as Revealed by Selective Inhibition

Abstract: Anandamide, an endogenous ligand for central cannabinoid receptors, is released from neurons on depolarization and rapidly inactivated. Anandamide inactivation is not completely understood, but it may occur by transport into cells or by enzymatic hydrolysis. The compound N-(4-hydroxyphenyl)arachidonylamide (AM404) was shown to inhibit high-affinity anandamide accumulation in rat neurons and astrocytes in vitro, an indication that this accumulation resulted from carrier-mediated transport. Although AM404 did not activate cannabinoid receptors or inhibit anandamide hydrolysis, it enhanced receptor-mediated anandamide responses in vitro and in vivo. The data indicate that carrier-mediated transport may be essential for termination of the biological effects of anandamide, and may represent a potential drug target.

Range of antinuclear antibodies in "healthy" individuals

Abstract: Objective. To determine the range of antinuclear antibodies (ANA) in “healthy” individuals compared with that in patients with systemic lupus erythematosus (SLE), systemic sclerosis (SSc; scleroderma), Sjogren's syndrome (SS), rheumatoid arthritis (RA), or soft tissue rheumatism (STR). Methods. Fifteen international laboratories experienced in performing tests for ANA by indirect immunofluorescence participated in analyzing coded sera from healthy individuals and from patients in the 5 different disease groups described above. Except for the stipulation that HEp-2 cells should be used as substrate, each laboratory used its own in-house methodology so that the data might be expected to reflect the output of a cross-section of worldwide ANA reference laboratories. The sera were analyzed at 4 dilutions: 1:40, 1:80, 1:160, and 1:320. Results. In healthy individuals, the frequency of ANA did not differ significantly across the 4 age subgroups spanning 20–60 years of age. This putatively normal population was ANA positive in 31.7% of individuals at 1:40 serum dilution, 13.3% at 1:80, 5.0% at 1:160, and 3.3% at 1:320. In comparison with the findings among the disease groups, a low cutoff point at 1:40 serum dilution (high sensitivity, low specificity) could have diagnostic value, since it would classify virtually all patients with SLE, SSc, or SS as ANA positive. Conversely, a high positive cutoff at 1:160 serum dilution (high specificity, low sensitivity) would be useful to confirm the presence of disease in only a portion of cases, but would be likely to exclude 95% of normal individuals. Conclusion. It is recommended that laboratories performing immunofluorescent ANA tests should report results at both the 1:40 and 1:160 dilutions, and should supply information on the percentage of normal individuals who are positive at these dilutions. A low-titer ANA is not necessarily insignificant and might depend on at least 4 specific factors. ANA assays can be a useful discriminant in recognizing certain disease conditions, but can create misunderstanding when the limitations are not fully appreciated.

Immunotherapy of tumors with autologous tumor-derived heat shock protein preparations

Abstract: Immunotherapy of mice with preexisting cancers with heat shock protein preparations derived from autologous cancer resulted in retarded progression of the primary cancer, a reduced metastatic load, and prolongation of life-span. Treatment with heat shock protein preparations derived from cancers other than the autologous cancer did not provide significant protection. Spontaneous cancers (lung cancer and melanoma), chemically induced cancers (fibrosarcoma and colon carcinoma), and an ultraviolet radiation-induced spindle cell carcinoma were tested, and the results support the efficacy of autologous cancer-derived heat shock protein-peptide complexes in immunotherapy of cancers without the need to identify specific tumor antigenic epitopes.

Middle Management’s Strategic Influence and Organizational Performance†

Abstract: This study investigated relationships between middle managers’ formal position, their strategic influence and organizational performance. Among the 259 middle managers represented in the study, managers with formal positions in boundary–spanning sub–units reported higher levels of strategic influence activity than others. At the organizational level of analysis, the study found that firm performance was associated with more uniform levels of downward strategic influence, and more varied levels of upward influence among middle management cohorts. The findings suggest that middle managers’ strategic influence arises from their ability to mediate between internal and external selection environments. In addition, positive effects on organizational performance appear to depend on: (1) whether the overall pattern of upward influence is conducive to shifts in the network centrality of individual managers; and (2) whether the pattern of downward influence is consistent with an appropriate balance between the organization’s need for control and flexibility.

Manganese oxide mesoporous structures: Mixed-valent semiconducting catalysts

Abstract: Hexagonal and cubic phases of manganese oxide mesoporous structures (MOMS) have been prepared by means of the oxidation of Mn(OH)2. The hexagonal MOMS materials form a hexagonal array of pores with an open porous structure, thick walls (1.7 nanometers), and exceptional thermal stability (1000°C). The walls of the mesopores are composed of microcrystallites of dense phases of Mn2O3 and Mn3O4, with MnO6 octahedra as the primary building blocks. The calcined hexagonal MOMS have an electrical conductivity of 8.13 × 10−6 per ohm·centimeter, an average manganese oxidation state of 3.55, and a band gap of 2.46 electron volts. Catalytic oxidations of cyclohexane and n-hexane in aqueous solutions in a batch reactor show conversions of ∼10 and ∼8 percent, respectively. Characterization and catalytic data suggest that MOMS systems show significant enhancement in thermal stability with respect to octahedral molecular sieve materials.

Heat Shock Protein–Peptide Complexes, Reconstituted In Vitro, Elicit Peptide-specific Cytotoxic T Lymphocyte Response and Tumor Immunity

Abstract: Heat shock protein (HSP) preparations derived from cancer cells and virus-infected cells have been shown previously to elicit cancer-specific or virus-specific immunity. The immunogenicity of HSP preparations has been attributed to peptides associated with the HSPs. The studies reported here demonstrate that immunogenic HSP-peptide complexes can also be reconstituted in vitro. The studies show that (a) complexes of hsp70 or gp96 HSP molecules with a variety of synthetic peptides can be generated in vitro; (b) the binding of HSPs with peptides is specific in that a number of other proteins tested do not bind synthetic peptides under the conditions in which gp96 molecules do; (c) HSP-peptide complexes reconstituted in vitro are immunologically active, as tested by their ability to elicit antitumor immunity and specific CD8+ cytolytic T lymphocyte response; and (d) synthetic peptides reconstituted in vitro with gp96 are capable of being taken up and re-presented by macrophage in the same manner as gp96- peptides complexes generated in vivo. These observations demonstrate that HSPs are CD8+ T cell response-eliciting adjuvants.

Fractures Attributable to Osteoporosis: Report from the National Osteoporosis Foundation

Abstract: To assess the cost-effectiveness of interventions to prevent osteoporosis, it is necessary to estimate total health care expenditures for the treatment of osteoporotic fractures. Resources utilized for the treatment of many diseases can be estimated from secondary databases using relevant diagnosis codes, but such codes do not indicate which fractures are osteoporotic in nature. Therefore, a panel of experts was convened to make judgments about the probabilities that fractures of different types might be related to osteoporosis according to patient age, gender, and race. A three-round Delphi process was applied to estimate the proportion of fractures related to osteoporosis (i.e., the osteoporosis attribution probabilities) in 72 categories comprised of four specific fracture types (hip, spine, forearm, all other sites combined) stratified by three age groups (45-64 years, 65-84 years, 85 years and older), three racial groups (white, black, all others), and both genders (female, male). It was estimated that at least 90% of all hip and spine fractures among elderly white women should be attributed to osteoporosis. Much smaller proportions of the other fractures were attributed to osteoporosis. Regardless of fracture type, attribution probabilities were less for men than women and generally less for non-whites than whites. These probabilities will be used to estimate the total direct medical costs associated with osteoporosis-related fractures in the United States.

Capabilities and Governance: The Rebirth of Production in the Theory of Economic Organization

Abstract: We argue that since Coase?s seminal 1937 paper on "The Nature of the Firm," there has been an odd and unjustified separation between price theory and the economics of organization. For example, matters of production has been the domain of the former exclusively. However, a new approach to economic organization, here called "the capabilities approach," that places production center-stage in the explanation of economic organization, is now emerging. We discuss the sources of this approach and its relation to the mainstream economics of organization.

Hierarchical Spatio-Temporal Mapping of Disease Rates

Abstract: Maps of regional morbidity and mortality rates are useful tools in determining spatial patterns of disease. Combined with sociodemographic census information, they also permit assessment of environmental justice; that is, whether certain subgroups suffer disproportionately from certain diseases or other adverse effects of harmful environmental exposures. Bayes and empirical Bayes methods have proven useful in smoothing crude maps of disease risk, eliminating the instability of estimates in low-population areas while maintaining geographic resolution. In this article we extend existing hierarchical spatial models to account for temporal effects and spatio-temporal interactions. Fitting the resulting highly parameterized models requires careful implementation of Markov chain Monte Carlo (MCMC) methods, as well as novel techniques for model evaluation and selection. We illustrate our approach using a dataset of county-specific lung cancer rates in the state of Ohio during the period 1968–1988.

Bone formation in vivo: comparison of osteogenesis by transplanted mouse and human marrow stromal fibroblasts.

Abstract: Background Marrow stromal fibroblasts (MSFs) are known to contain bone precursor cells. However, the osteogenic potential of human MSFs has been poorly characterized. The aim of this study was to compare the osteogenic capacity of mouse and human MSFs after implantation in vivo. Methods After in vitro expansion, MSFs were loaded into a number of different vehicles and transplanted subcutaneously into immunodeficient mice. Results Mouse MSFs transplanted within gelatin, polyvinyl sponges, and collagen matrices all formed a capsule of cortical-like bone surrounding a cavity with active hematopoiesis. In transplants of MSFs from transgenic mice harboring type I procollagen-chloramphenicol acetyltransferase constructs, chloramphenicol acetyltransferase activity was maintained for up to 14 weeks, indicating prolonged bone formation by transplanted MSFs. New bone formation by human MSFs was more dependent on both the in vitro expansion conditions and transplantation vehicles. Within gelatin, woven bone was observed sporadically and only after culture in the presence of dexamethasone and L-ascorbic acid phosphate magnesium salt n-hydrate. Consistent bone formation by human MSFs was achieved only within vehicles containing hydroxyapatite/tricalcium phosphate ceramics (HA/TCP) in the form of blocks, powder, and HA/TCP powder-type I bovine fibrillar collagen strips, and bone was maintained for at least 19 weeks. Cells of the new bone were positive for human osteonectin showing their donor origin. HA/TCP powder, the HA/TCP powder-type I bovine fibrillar collagen strips, and HA/TCP powder held together with fibrin were easier to load and supported more extensive osteogenesis than HA/TCP blocks and thus may be more applicable for therapeutic use. Conclusions In this article, we describe the differences in the requirements for mouse and human MSFs to form bone, and report the development of a methodology for the consistent in vivo generation of extensive bone from human MSFs.

Alternate Assembly of Ordered Multilayers of SiO2 and Other Nanoparticles and Polyions

Abstract: Alternate layer-by-layer assembly of colloidal SiO2 particles with polycations has been investigated by quartz crystal microbalance (QCM), scanning electron microscopy (SEM), and atomic force microscopy (AFM). QCM measurement confirmed the high regularity and reproducibility of the assembling process that depends on particle concentration, particle size, and ionic strength. The individual adsorption step was completed within 15 s. The thickness of adsorbed layers increased with increasing SiO2 concentrations at the three particle sizes used (45, 25, and 78 nm in diameter), unlike the case for other polyion assemblies. It also increased with increasing ionic strength of aqueous SiO2 dispersions. According to SEM observation, the assembled film possessed surprisingly flat surfaces at optimized ionic strengths. AFM observation revealed that SiO2 particles were not closely packed. The neutralization ratio of SiO2 and PDDA was estimated by turbidity measurement. Comparison of turbidity and QCM data indicated t...

Classical conditioning and the placebo effect

Abstract: Stimulus substitution models posit that placebo responses are due to pairings of conditional and unconditional stimuli. Expectancy theory maintains that conditioning trials produce placebo response expectancies, rather than placebo responses, and that the expectancies elicit the responses. We tested these opposing models by providing some participants with information intended to impede the formation of placebo expectancies during conditioning trials and by assessing placebo expectancies. Although conditioning trials significantly enhanced placebo responding, this effect was eliminated by adding expectancies to the regression equation, indicating that the effect of pairing trials on placebo response was mediated completely by expectancy. Verbal information reversed the effect of conditioning trials on both placebo expectancies and placebo responses, and the magnitude of the placebo effect increased significantly over 10 extinction trials. These data disconfirm a stimulus substitution explanation and provide strong support for an expectancy interpretation of the conditioned placebo enhancement produced by these methods.

Serotonin transporter protein (SLC6A4) allele and haplotype frequencies and linkage disequilibria in African- and European-American and Japanese populations and in alcohol-dependent subjects

Abstract: The SLC6A4 locus encodes the serotonin transporter, which in turn mediates the synaptic inactivation of the neurotransmitter serotonin. Two PCR-formatted polymorphisms at this locus have been described, the first of which is a variable number tandem repeat located in exon 2, and the second a repeat sequence polymorphism located in the promoter region. The latter polymorphism alters transcriptional activity of SLC6A4, and has been reported to be associated with anxiety and depression-related traits. We studied allele frequencies, and computed haplotype frequencies and linkage disequilibrium measures, for these two polymorphisms in European-American, African-American, and Japanese populations, and in a set of alcohol-dependent European-American subjects. Allele frequencies for both systems showed variation, with significant differences overall for each system, and significant differences between each pair of populations for both systems. Linkage disequilibrium also varied among the populations. There were no significant differences in allele or haplotype frequencies between the European-American population samples and alcohol-dependent subjects. The population differences demonstrate a potential for population stratification in association studies of either of these SLC6A4 polymorphisms. If genetic variation at this locus really is associated with behavioral variation, these results could reflect either different behavioral adaptations in different populations, or random genetic drift of a behaviorally important but selectively neutral polymorphism.

Close relationships and elevated HIV risk behavior: Evidence and possible underlying psychological processes.

Abstract: A review of research on AIDS preventive behavior indicates that minority and nonminority heterosexual adolescents and adults, gay men, injection drug users, and commercial sex workers are all less ...

Iron and grazing constraints on primary production in the central equatorial Pacific: An EqPac synthesis

Abstract: Recent studies in the central equatorial Pacific allow a comprehensive assessment of phytoplankton regulation in a high-nutrient, low-chlorophyll (HNLC) ecosystem. Elemental iron enters the euphotic zone principally via upwelling and is present at concentrations (530 PM) well below the estimated half-saturation constant (120 PM) for the large cells that bloom with iron enrichment. In addition, the meridional trend in quantum yield of photosynthesis suggests that even the dominant small phytoplankton are held below their physiological potential by iron deficiency. Grazing by microzooplankton dominates phytoplankton losses, accounting for virtually all of the measured phytoplankton production during El Nina conditions and -66% during normal upwelling conditions, with mesozooplankton grazing and lateral advection closing the balance. Nitrate uptake is strongly correlated with the pigment biomass of diatoms, which increase in relative abundance during normal upwelling conditions. Nonetheless, the f-ratio remains low (0.07-0.12) under all conditions. Iron budgets are consistent with the notions that new production is determined by the rate of new iron input to the system while total production depends on efficient iron recycling by grazers. Although the limiting substrates differ, the interactions of resource limitation and grazing in HNLC regions are conceptually similar to the generally accepted view for oligotrophic subtropical regions. In both systems, small dominant phytoplankton grow at rapid, but usually less than physiologically maximal, rates; they are cropped to low stable abundances by microzooplankton; and their sustained high rates of growth depend on the remineralized by-products of grazing.

Nitrogen loading from coastal watersheds to receiving estuaries: new method and application

Abstract: In this paper we develop a model to estimate nitrogen loading to watersheds and receiving waters, and then apply the model to gain insight about sources, losses, and transport of nitrogen in groundwater moving through a coastal watershed. The model is developed from data of the Waquoit Bay Land Margin Ecosystems Research project (WBLMER), and from syntheses of published information. The WBLMER nitrogen loading model first estimates inputs by atmospheric deposition, fertilizer use, and wastewater to surfaces of the major types of land use (natural vegetation, turf, agricultural land, residential areas, and impervious surfaces) within the landscape. Then, the model estimates losses of nitrogen in the various compartments of the watershed ecosystem. For atmospheric and fertilizer nitrogen, the model allows losses in vegetation and soils, in the vadose zone, and in the aquifer. For wastewater nitrogen, the model allows losses in septic systems and effluent plumes, and it adds further losses that occur during diffuse transport within aquifers. The calculation of losses is done separately for each major type of land cover, because the processes and loss rates involved differ for different tesserae of the land cover mosaic. If groundwater flows into a freshwater body, the model adds a loss of nitrogen for traversing the freshwater body and then subjects the surviving nitrogen to losses in the aquifer. The WBLMER model is developed for Waquoit Bay, but with inputs for local conditions it is applicable to other rural to suburban watersheds underlain by unconsolidated sandy sediments. Model calculations suggest that the atmosphere contributes 56%, fertilizer 14%, and wastewater 27% of the nitrogen delivered to the surface of the watershed of Waquoit Bay. Losses within the watershed amount to 89% of atmospheric nitrogen, 79% of fertilizer nitrogen, and 65% of wastewater nitrogen. The net result of inputs to the watershed surface and losses within the watershed is that wastewater becomes the largest source (48%) of nitrogen loads to receiving estuaries, followed by atmospheric deposition (30%) and fer- tilizer use (15%). The nitrogen load to estuaries of Waquoit Bay is transported primarily through land parcels covered by residential areas (39%, mainly via wastewater), natural vegetation (21%, by atmospheric deposition), and turf (16%, by atmospheric deposition and fertilizers). Other land covers were involved in lesser throughputs of nitrogen. The model results have implications for management of coastal landscapes and water quality. Most attention should be given to wastewater disposal within the watershed, par- ticularly within 200 m of the shore. Rules regarding setbacks of septic system location relative to shore and nitrogen retention ability of septic systems, will be useful in control of wastewater nitrogen loading. Installation of multiple conventional leaching fields or septic systems in high-flow parcels could be one way to increase nitrogen retention. Control of fertilizer use can help to a modest degree, particularly for optional uses such as lawns situated near shore. Conservation of parcels of accreting natural vegetation should be given high priority, because these environments effectively intercept atmospheric deposition. Areas upgradient from freshwater bodies should be given low priority in plans to control nitrogen loading, because ponds intercept much of the nitrogen transported from upgradient.

Statistical power analysis in wildlife research

Abstract: Statistical power analysis can be used to increase the efficiency of research efforts and to clarify research results. Power analysis is most valuable in the design or planning phases of research efforts. Such prospective (a priori) power analyses can be used to guide research design and to estimate the number of samples necessary to achieve a high probability of detecting biologically significant effects. Retrospective (a posteriori) power analysis has been advocated as a method to increase information about hypothesis tests that were not rejected. However, estimating power for tests of null hypotheses that were not rejected with the effect size observed in the study is incorrect; these power estimates will always be ≤0.50 when bias adjusted and have no relation to true power. Therefore, retrospective power estimates based on the observed effect size for hypothesis tests that were not rejected are misleading; retrospective power estimates are only meaningful when based on effect sizes other than the observed effect size, such as those effect sizes hypothesized to be biologically significant. Retrospective power analysis can be used effectively to estimate the number of samples or effect size that would have been necessary for a completed study to have rejected a specific null hypothesis. Simply presenting confidence intervals can provide additional information about null hypotheses that were not rejected, including information about the size of the true effect and whether or not there is adequate evidence to accept a null hypothesis as true. We suggest that (1) statistical power analyses be routinely incorporated into research planning efforts to increase their efficiency, (2) confidence intervals be used in lieu of retrospective power analyses for null hypotheses that were not rejected to assess the likely size of the true effect, (3) minimum biologically significant effect sizes be used for all power analyses, and (4) if retrospective power estimates are to be reported, then the α-level, effect sizes, and sample sizes used in calculations must also be reported.

A generalized S-D assignment algorithm for multisensor-multitarget state estimation

Abstract: We develop a new algorithm to associate measurements from multiple sensors to identify the real targets in a surveillance region, and to estimate their states at any given time. The central problem in a multisensor-multitarget state estimation problem is that of data association-the problem of determining from which target, if any, a particular measurement originated. The data association problem is formulated as a generalized S-dimensional (S-D) assignment problem, which is NP-hard for S/spl ges/3 sensor scans (i.e., measurement lists). We present an efficient and recursive generalized S-D assignment algorithm (S/spl ges/3) employing a successive Lagrangian relaxation technique, with application to the localization of an unknown number of emitters using multiple high frequency direction finder sensors (S=3, 5, and 7).

Frequent short rest breaks from computer work: effects on productivity and well-being at two field sites

Abstract: Computer operators at two work sites (n = 73, n = 19) were prompted to take three 30-s and one 3-min break from computer work each hour in addition to conventional rest breaks. Some operators were asked to perform stretching exercises during the short breaks. Mood state and musculoskeletal discomfort were assessed at each work site over a 2- or 3-week baseline period and a 4- or 6-week treatment period, respectively. Operator productivity measures were obtained from company records. Operators complied with about half of the added breaks but favoured 3-min breaks over 30-s breaks. No improvement in productivity or well-being was found at the larger work site. At the smaller work site, productivity, eye, leg and foot comfort all improved when the short breaks included stretching exercises. These results provide evidence that frequent short breaks from continuous computer-mediated work can benefit worker productivity and well-being when the breaks integrate with task demands.

Relative standing and the performance of recently acquired European firms

Abstract: This study draws on the concepts of relative standing to explain the post-merger performance of recently acquired European firms. We used a 2 x 3 sampling design where we surveyed top managers of British and French firms that were acquired by British, French, and U.S. firms as to their perceptions of cultural compatibility with the buying firms, their sense of loss of autonomy since the merger, and post-merger performance. While we found that the theory adequately explains the post-merger performance of both British and French firms, suggesting that this primarily 'made-in-the-United States' organization theory extends beyond the cultural domain of the United States, we also found an aspect of the theory that reflects a possible cultural bias. ? 1997 by John Wiley & Sons, Ltd.

Effect of recombinant human insulin-like growth factor-I on progression of ALS A placebo-controlled study

Abstract: The objective of this study was to investigate the safety and efficacy of recombinant human insulinlike growth factor-I (rhIGF-I) in the treatment of sporadic ALS A double-blind, placebo-controlled, randomized study of 266 patients was conducted at eight centers in North America Placebo or rhIGF-I (005 mg/kg/day or 010 mg/kg/day) was administered for 9 months The primary outcome measure was disease symptom progression, assessed by the rate of change (per patient slope) in the Appel ALS rating scale total score The Sickness Impact Profile (SIP), a patient-perceived, health-related quality of life assessment, was a secondary outcome variable Progression of functional impairment in patients receiving high-dose (010 mg/kg/day) rhIGF-I was 26% slower than in patients receiving placebo (p = 001) The high-dose treatment group was less likely to terminate the study due to protocol-defined markers of disease symptom progression, and members in this group exhibited a slower decline in quality of life, as assessed by the SIP Patients receiving 005 mg/kg/day of rhIGF-I exhibited trends similar to those associated with high-dose treatment, suggesting a dose-dependent response The incidence of clinically significant adverse experiences was comparable among the three treatment groups Recombinant human insulin-like growth factor-I slowed the progression of functional impairment and the decline in health-related quality of life in patients with ALS with no medically important adverse effects

Intestinal absorption and tissue distribution of carotenoids

Abstract: Human metabolism of carotenoids is of interest not only because of the provitamin A function of certain carotenoids, but also because these compounds have been associated with reducing risks of certain cancers and chronic diseases. Full understanding of carotenoid metabolism is complicated by a number of factors: variations in physiochemical properties among carotenoids; altered carotenoid utilization as a result of the normal vicissitudes of lipid absorption and transport; divergence in metabolic fate within the intestinal enterocyte (especially carotenoid cleavage to retinoids); differences in packaging and transport in lipoproteins; dissimilarity in tissue uptake of specific carotenoids; and the possible isomerization of carotenoids within tissues. Hampering research progress is the lack of animal models that perfectly mimic human carotenoid metabolism and the limited number of carotenoids approved for human consumption in a pure form. It is clear, however, that diet affects carotenoid absorption. The efficient digestion and absorption of dietary fat, as well as the presence of bile salt micelles, is essential for carotenoid absorption. Competition among carotenoids and other dietary components for absorption, transport, and uptake by tissues is documented but needs further research. From limited data it seems that the more polar carotenoids (xanthophylls) may be absorbed more efficiently than are carotenes (hydrocarbon carotenoids). The mechanism in humans for the phenomenon of “nonresponders” to oral doses of β-carotene requires further study to determine whether it is an effect of inefficient absorption or of intestinal cleavage of β-carotene. The delayed maxima in plasma carotenoid concentrations after ingestion, relative to plasma triacylglycerol, are explainable as secondary secretion of carotenoids transferred to other lipoproteins after chylomicron clearance. The site and degree of isomerization of carotenoids after consumption has not yet been defined. In this article the absorption, transport, and tissue uptake of carotenoids will be reviewed and possible differences among carotenoids and factors influencing their utilization will be discussed.