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At least 685 records · Page 38Linked to original sources
PubMed2001

Characterization of modified low density lipoprotein subfractions by capillary isotachophoresis.

Oxidative modification of low density lipoproteins (LDLs) is an important pathogenetic factor in atherosclerosis. The various steps in oxidative modifications of LDL can be monitored using different methodologies with varying degrees of complexity. In this study, we propose capillary isotachophoresis (CITP) as a suitable tool to detect and measure the degree of oxidation of LDL. LDL was isolated from pooled plasma of healthy volunteers by sequential ultracentrifugation, and oxidation was performed in vitro as well as in cell culture experiments. Native LDL and oxidatively modified LDL were characterized by apo B-100 fluorescence and conjugated diene formation. Samples were separated by CITP combined with sudan black B staining. To underline the inherent advantages of this approach, CITP was compared with classical lipoprotein electrophoresis using agarose gel. We demonstrate the CITP method to be highly sensitive, as changes in peak area of the separated LDL subfractions were detected after only 2 h of oxidation. The leading LDL peaks increased, while the terminating LDL peaks decreased in parallel throughout the duration of oxidation. The LDL samples, oxidized for 4-24 h, also exhibited an increased migration velocity of the fractions. In summary, we present the first study investigating LDL-subfractions separated by CITP and the alterations of these LDL-subfractions after gradual in vitro oxidation and after oxidative modification by monocyte-derived macrophages and vascular smooth muscle cells.

Apolipoprotein B-100↗
PubMedDate not supplied

Adaptive designs for pivotal trials: discussion points from the PSI Adaptive Design Expert Group.

The Committee for Medicinal Products for Human Use (CHMP) is currently preparing a guideline on 'methodological issues in confirmatory clinical trials with flexible design and analysis plan'. PSI (Statisticians in the Pharmaceutical Industry) sponsored a meeting of pharmaceutical statisticians with an interest in the area to share experiences and identify potential opportunities for adaptive designs in late-phase clinical drug development. This article outlines the issues raised, resulting discussions and consensus views reached. Adaptive designs have potential utility in late-phase clinical development. Sample size re-estimation seems to be valuable and widely accepted, but should be made independent of the observed treatment effect where possible. Where unblinding is necessary, careful consideration needs to be given to preserving the integrity of the trial. An area where adaptive designs can be particularly beneficial is to allow dose selection in pivotal trials via adding/dropping treatment arms; for example, combining phase II and III of the drug development program. The more adaptations made during a late-phase clinical trial, the less likely that the clinical trial would be considered as a confirmatory trial. In all cases it would be advisable to consult with regulatory agencies at the protocol design stage. All involved should remain open to scientifically valid opportunities to improve drug development.

Clinical Trials as Topic↗
PubMed2005

External quality assurance programme for enzymatic analysis of lysosomal storage diseases: a pilot study.

Inborn errors of metabolism are rare and laboratories performing diagnostic tests in this field must participate in external quality assurance (EQA) schemes to demonstrate their competence and also to maintain sufficient experience with patient material. EQA schemes for metabolite analyses are available (ERNDIM), but corresponding EQA schemes for enzyme analyses are nonexistent. In this paper we describe a pilot study on lysosomal enzyme testing by four centres in The Netherlands. Quantitative aspects of EQA were studied by interlaboratory comparison of activities of six lysosomal enzymes in a series of buffy coat samples. Interlaboratory variance was enormous. To reduce variance caused by methodological differences, participants reported enzyme activities relative to mean normal values. Beta-D-Galactosidase activities compared well between the participating laboratories (average interlaboratory CV 13%), but for other enzymes large differences were observed, e.g. sphingomyelinase (average CV 38%). Diagnostic proficiency was tested with cultured fibroblasts. In 45 out of a total of 48 tests (12 cell lines, 4 participants) the correct diagnosis was accomplished on the basis of merely biochemical investigations, i.e. without clinical data of the patients. In a survey using blood of a late-onset Pompe disease patient, less conclusive results were obtained. A stable enzyme source was developed for easy distribution. Most lysosomal enzymes were stable upon lyophilization of leukocyte homogenates and during subsequent storage of the freeze-dried material at room temperature, in particular when cryolyoprotectant was added. Shipment of such lyophilized samples is simple and cheap and ideal for an EQA scheme. Our study shows that an EQA programme for enzymatic testing of lysosomal storage diseases is necessary to accomplish reliable diagnostic procedures for lysosomal storage diseases. We recommend that EQA for lysosomal enzymes be implemented through ERNDIM.

Blood↗
PubMed2005

Effect of mineral content on the nanoindentation properties and nanoscale deformation mechanisms of bovine tibial cortical bone.

In this paper, a multitechnique experimental and numerical modeling methodology was used to show that mineral content had a significant effect on both nanomechanical properties and ultrastructural deformation mechanisms of samples derived from adult bovine tibial bone. Partial and complete demineralization was carried out using phosphoric and ethylenediamine tetraacetic acid treatments to produce samples with mineral contents that varied between 37 and 0 weight percent (wt%). The undemineralized samples were found to have a mineral content of approximately 58 wt%. Nanoindentation experiments (maximum loads approximately 1000 microN and indentation depths approximately 500 nm) perpendicular to the osteonal axis for the approximately 58 wt% samples were found to have an estimated elastic modulus of approximately 7-12 GPa, which was 4-6x greater than that obtained for the approximately 0 wt% samples. The yield strength of the approximately 58 wt% samples was found to be approximately 0.24 GPa; 3.4x greater than that of the approximately 0 wt% sample. These results are discussed in the context of in situ and post-mortem atomic force microscopy imaging studies which show clear residual deformation after indentation for all samples studied. The partially demineralized samples underwent collagen fibril deformation and kinking without loss of the characteristic banding structure at low maximum loads (approximately 300 microN). At higher maximum loads (approximately 700 microN) mechanical denaturation of collagen fibrils was observed within the indent region, as well as disruption of interfibril interfaces and slicing through the thickness of individual fibrils leading to microcracks along the tip apex lines and outside the indent regions. A finite element elastic-plastic continuum mechanical model was able to predict the nanomechanical behavior of all samples on loading and unloading.

Animals↗
PubMed2001

Control genes in quantitative molecular biological techniques: the variability of invariance.

The measurement of transcript levels constitutes the foundation of today's molecular genetics. Independent of the techniques used, quantifications are generally normalised using invariant control genes to account for sample handling, loading and experimental variation. All of the widely used control genes are evaluated, dissecting different methodological approaches and issues regarding the experimental context (e.g. development and tissue type). Furthermore, the major sources of error are highlighted when applying these techniques. Finally, different approaches undertaken to assess the invariance of control genes are critically analysed to generate a procedure that will help to discern the best control for novel experiments.

Actins↗
PubMed2001

Testing hypotheses on specific environmental causal effects on behavior.

There have been strong critiques of the notion that environmental influences can have an important effect on psychological functioning. The substance of these criticisms is considered in order to infer the methodological challenges that have to be met. Concepts of cause and of the testing of causal effects are discussed with a particular focus on the need to consider sample selection and the value (and limitations) of longitudinal data. The designs that may be used to test hypotheses on specific environmental risk mechanisms for psychopathology are discussed in relation to a range of adoption strategies, twin designs, various types of "natural experiments," migration designs, the study of secular change, and intervention designs. In each case, consideration is given to the need for samples that "pull-apart" variables that ordinarily go together, specific hypotheses on possible causal processes, and the specification and testing of key assumptions. It is concluded that environmental risk hypotheses can be (and have been) put to the test but that it is usually necessary to use a combination of research strategies.

Adult↗
PubMed1982

Measurement of aquatic biodegradation rates by determining heterotrophic uptake of radiolabeled pollutants.

The heterotrophic uptake technique was modified to provide a rapid and simple technique for estimating the rates of biodegradation of organic pollutants under environmental conditions. The methodology is based on an evaluation of uptake into cells and subsequent respiration of radiolabeled organic substrates in short-term experiments. The resulting data can be used to calculate either turnover times or, if multiple concentrations of substrate are used, kinetic parameters. The procedure was applied to assess the biodegradation rates of m-cresol, chlorobenzene, nitrilotriacetic acid, and 1,2,4-trichlorobenzene in fresh, brackish, and marine water samples from the coastal areas of North Carolina. Saturation kinetics for uptake were obtained with each of the compounds tested. Rates of metabolism were shown to be dependent on sample location and time of year.

Biodegradation, Environmental↗
PubMed2003

Assault of long-term care personnel.

The purpose of this study was to explore contributing factors, consequences, and solutions to assault of long-term care personnel. The study sample consisted of three focus groups composed of certified nursing assistants and administrators employed in long-term care facilities within a large Midwestern city. Using content analysis methodology, multiple themes emerged: worker attitude, vulnerability, work culture, job tasks, training, working short-staffed, financial concerns, changes in social values and health care, community crime, substance abuse, accepting assaults, coworker threats, issues of retaliation, professional withdrawal, and inability to share experiences. Preventive measures suggested by the participants are consistent with those recommended by the Occupational Safety and Health Administration. Implications for staff and administrators include both personal and workplace strategies. Recommendations include implementing more comprehensive violence prevention programs that includes conflict management and training tailored to the type of residents.

Aged↗
PubMed1988

Conceptions of rape.

Where previous studies have examined attitudes and perceptions of the rape act, we have attempted to delve into the meanings which people impute at a less conscious level. Using Semantic Differential methodology, a stratified sample of participants rated the concepts of "assault," "rape," "seduction" and "love-making"; these were chosen along an underlying dimension of violence/coercion. Analysis incorporating the blocking variables (gender X SES) and other demographic personal information demonstrated that: "assault/rape" and "seduction/love-making" were seen as similar; "rape/seduction" as somewhat similar; and "assault/love-making" and "rape/love-making" as dissimilar. In general, important demographic/personal variables yielded no interpretable results. However, "prior rape experience" influenced participants' conceptions of the act of rape significantly. This result is discussed in light of some mixed results of previous studies in this area. We also present suggestions for interventions, based on the findings of this study.

Adult↗
PubMedDate not supplied

Parental perspectives related to decision-making and neonatal death.

With the advent of many new technologies, decision-making about the care of critically ill neonates represents one of the primary ethical arenas in health care today. Professionals and parents are forced to make decisions about when, how, and if critically ill neonates die. This qualitative study, based on interviews with a very small, convenience sample of parents, begins to explore the parental perspective about ethical decision-making regarding critically ill neonates by describing their personal experiences as they faced the reality or possibility of their babies' deaths.

Attitude to Death↗
PubMed2000

Bisphosphonates and the prevention of metastasis: first evidences from preclinical and clinical studies.

BACKGROUND: Bisphosphonates have been used successfully for many years in the treatment of hypercalcemia and to reduce skeletal-related complications of metastases. In the first years of bisphosphonate use, the efficacy of these substances was thought to lie purely in the inhibition of osteoclasts. However, there is recent evidence to suggest that an antitumor effect also may play a role. As well as having an apoptotic and antiproliferative effect on osteoclasts, bisphosphonates may exert a similar influence on macrophages and tumor cells. METHODS: The current investigation summarizes all results published to date that deal with the potential antitumor properties of the bisphosphonates. On the one hand, these include results from basic research into the action mechanism and preventative models in animals. In addition, the results of initial clinical experience with metastasis prophylaxis with bisphosphonates in breast carcinoma patients are presented and interpreted. RESULTS: Improvements in the survival time of certain subpopulations have been found in many Phase III studies with bisphosphonates to date, both in the setting of metastatic breast carcinoma and in multiple myeloma. Some preclinical studies showed that down-regulation of bone metabolism by bisphosphonates is associated with a lower incidence of bone metastases and destruction in animals, whereas activation is correlated with a higher number of metastases. However, varying results were found in animal experiments with regard to the effect of bisphosphonates on the incidence and growth pattern of nonosseous metastases. The results of three randomized studies in patients with primary breast carcinoma in which patients received 1600 mg clodronate orally have now been evaluated and presented. All three studies arrived at different results. Because the dose was identical in all three studies, the differing results can only be either random or methodologic (inclusion criteria, sample size, etc.). CONCLUSIONS: Overall, the results are very promising but need confirmation in further studies. At the moment, we have more open than answered questions. First, it is unclear whether this type of adjuvant therapy with bisphosphonates should be given continually by the oral route, or whether an intravenous interval therapy could produce the same results. It is also uncertain whether the doses used in a palliative setting are optimal or whether lower doses might also suffice. The optimum period of adjuvant treatment is also subject to debate. What is clear, however, is that confirmation of the initial clinical results will open a new chapter in the treatment of malignant tumors.

Animals↗
PubMed1986

Life event stress and coping style as contributors to psychopathology.

Despite the nearly universal finding that life event stress is related to psychopathology, the strength of these relationships is weak. In an attempt to increase the strength of the correlation between life event stress and psychopathology, this study evaluated the simultaneous contribution of life event stress and coping style, as well as the independent contribution of each, to psychopathology. Seventy-six male and 74 female college students served as primary subjects, while an additional 57 male and 60 female college students served as a cross validation sample. Each subject completed the Life Experiences Survey, the Coping Strategies Inventory, and the MMPI. Sex differences were found in the type of coping style related to psychopathology, the relative contributions of coping style and negative life stress to psychopathology, and the percentage of variance accounted for in psychopathology. Future research was recommended to include other variables, such as chronic life stress and physiological reactivity, and to control better for such methodological problems as response sets.

Adaptation, Psychological↗
PubMed1997

Technology assessment using the association between outcome measures and patterns of illness severity.

The inclusion of a patient's illness experience as outcome in the assessment of health care technology has revealed methodological limitations such as the interpretation of multi-attribute scores and lack of knowledge about the association between illness and disease information. In an attempt to overcome these limitations, a cross-sectional study is performed to search for patterns of illness severity and investigate the association between illness measures and between illness patterns and disease factors. A sample of 211 patients with ulcerative colitis is studied using the sickness impact profile (SIP) and the rating form for inflammatory bowel disease patient concerns (RFIPC) as illness measures. SIP and RFIPC scores show low association, suggesting that they provide complementary information about the patient's illness status. Cluster analysis is performed using the two measures of illness separately to identify groups of patients with different degrees of severity of illness (clusters). The cluster description covers illness, disease and social and demographic variables. The RFIPC clusters show a general pattern of ascendant rank scores for the RFIPC items. SIP clusters differ, not only in the level of severity, but also in specific types of disability. The patients in the clusters with the highest degree of disability (reflected by SIP) show a non-linear relationship with patients' concerns (reflected by RFIPC) and disease factors.

Adult↗
PubMed2001

Detecting differentially expressed genes in multiple tag sampling experiments: comparative evaluation of statistical tests.

The comparison of several statistical methods currently used for detection of differentially expressed genes was attempted both by a simulation approach and by the analysis of data sets of human expressed sequence tags, obtained from UniGene. In the simulated mixed case, mimicking a situation close to reality, the general chi(2) test was unexpectedly the most efficient in multiple tag sampling experiments, especially when dealing with variations affecting weakly expressed genes. On the other hand, Audic and Claverie's method proved the most efficient for detecting differences in gene expression when dealing with pairwise comparisons. By applying the above methods on UniGene-based data sets concerning two human kidney tumours compared with normal kidney tissue, three novel genes overexpressed in these tumours were identified. Software and additional information on statistical methodologies, simulation approach and data are available at http://telethon.bio.unipd.it/bioinfo/IDEG6/.

Animals↗
PubMed2001

Risk factors for posttrauma reactions in police officers: a longitudinal study.

This prospective, longitudinal study investigated risk factors in the development of psychological ill health and posttraumatic stress symptoms in a sample of 223 junior police officers. Participants were assessed using a self-report methodology during training and again 12 months later on a range of personality, trauma exposure, and symptom measures. Risk factors for general psychological ill health at phase 2 of the research were found to comprise mostly stable, preexisting characteristics such as personality style, gender, and trait dissociation. Conversely, specific traumatic stress symptoms were more heavily influenced by experiences in the intervening 12 months, such as severity of incident exposure and peritraumatic dissociation. The implications for differential intervention are discussed.

Adult↗
PubMed2006

Sexual offenders' state-of-mind regarding childhood attachment: a controlled investigation.

Attachment experiences have been regarded as significant by researchers and clinicians attempting to explain the etiology of sexual offending. Although initial studies have revealed some promising evidence, there are a number of theoretical and methodological problems with this preliminary body of work. While addressing these limitations, the goal of the present study was to investigate state-of-mind regarding childhood attachment among subtypes of sexual offenders, comparing them to both a sample of nonsexual offenders and to the documented patterns of nonoffenders. Sixty-one sexual offenders (extrafamilial child molesters, incest offenders, and rapists) and 40 nonsexual offenders (violent and nonviolent) were administered the "Adult Attachment Interview." Results indicated that the majority of sexual offenders were insecure, representing a marked difference from normative samples. Although insecurity of attachment was common to all groups of offenders, there were important differences in regard to the specific type of insecurity. Most notable were the child molesters, who were significantly more likely to be Preoccupied. Rapists, violent offenders, and, to a lesser degree, incest offenders were more likely to be Dismissing. Although still most likely to be Dismissing, nonviolent offenders were comparatively more Secure.

Adult↗
PubMed1977

Socialization and the human physiologic response to crowding.

Cross-sectional data were analyzed for a possible relationship between household densities and physiologic alteration, based on socialization experiences with siblings in an earlier home environment. The measure of household density was persons-per-room and the measure of physiologic alteration was urinary vanillylmandelic acid. The results show an interaction between number-of-sibs and number-of-younger-sibs, with a statistically significant positive correlation between household densities and VMA values for subjects with fewer total sibs and no younger sibs, while a negative correlation was observed for subjects with one or more younger sibs. One possible interpretation of these results is that the physiologic response to crowding in humans is dependent at least in part on the earlier socialization experiences of the individual.

Cross-Sectional Studies↗
PubMed1994

The resampling method of statistical analysis.

Some non-statisticians occasionally use improper statistical methodology due to a lack of appreciation for the model assumptions that underlie a particular technique. The resampling method is a recent attempt to solve statistical problems with a minimum of assumptions. In essence, resampling involves an intuitive approach to inferential statistics that obviates the need for the mathematically derived sampling distribution. The resampling approach takes advantage of readily accessible high-speed computers to do a computationally intensive Monte Carlo experiment on the available data. The resampling approach liberates the user from imposing assumptions that are sometimes dubious. It also directs one away from a black-box attitude toward statistical analysis and instead forces the user to consider the purpose of the inferential process. A particularly user-friendly implementation of resampling methods that addresses some of the problems faced by non-statisticians is found in a simple, yet powerful, computer program called "Resampling Stats," version 3.13.

Adult↗