Showing papers by "Drexel University published in 1994"

Comprehensive QA for radiation oncology: report of AAPM Radiation Therapy Committee Task Group 40.

Abstract: Published by the American Association of Physicists in Medicine DISCLAIMER: This publication is based on sources and information believed to be reliable, but the AAPM and the editors disclaim any warranty or liability based on or relating to the contents of this publication. The AAPM does not endorse any products, manufacturers, or suppliers. Nothing in this publication should be interpreted as implying such endorsement. PREFACE This document is the report of a task group of the Radiation Therapy Committee of the American Association of Physicists in Medicine and supersedes the recommendations of AAPM Report 13 (AAPM, 1984). The purpose of the report is twofold. First, the advances in radiation oncology in the decade since AAPM Report 13 (AAPM, 1984) necessitated a new document on quality assurance (QA). Second, developments in the principles of quality assurance and continuing quality improvement necessitated a report framed in this context. The title \" Comprehensive Quality Assurance for Radiation Oncology \" may need clarification. While the report emphasizes the physical aspects of QA and does not attempt to discuss issues that are essentially medical (e.g., the decision to treat, the prescription of dose), it by no means neglects issues in which the physical and medical issues intertwine, often in a complex manner. The integrated nature of QA in radiation oncology makes it impossible to consider QA as limited to, for example, checking machine output or calibrating brachytherapy sources. QA activities cover a very broad range, and the work of medical physicists in this regard extends into a number of areas in which the actions of radiation oncologists, radiation therapists, 1 dosimetrists, accelerator engineers, and medical physicists are important. Moreover, this is true for each of the disciplines-each has special knowledge and expertise which affects the quality of treatment , and each discipline overlaps the others in a broad \" gray zone. \" It is important not only to understand each discipline's role in QA, but to clarify this zone so that errors do not \" fall between the cracks. \" This report therefore attempts to cover the physical aspects of QA both in a narrow or traditional sense and in a more integrated sense. The report comprises 2 parts: Part A is for administrators, and Part B is a code of practice in six sections. The first section of Part B describes a comprehensive quality assurance program in which the importance of a written procedural …

Diagnosing Personality Disorders: A Review of Issues and Research Methods

Abstract: Many questions face researchers conducting personality disorder research. Which measure should be used? When should patients be evaluated--at initial presentation when they are still symptomatic, or after symptom resolution? Can a patient accurately describe his or her personality, or must an informant be contacted? What do you do when personality traits change during an individual's lifetime? I discuss these and other issues of personality disorder assessment in the DSM-III/DSM-III-R era, and examine the empiric literature bearing on these questions. First, I review studies of diagnostic reliability and stability, because studies of the above questions can only be interpreted in the context of the limitations imposed by modest reliability.

Locus coeruleus neurons in monkey are selectively activated by attended cues in a vigilance task

Abstract: Impulse activity was recorded extracellularly from noradrenergic neurons in the nucleus locus coeruleus (LC; 47 single-cell and 126 multicell recordings) of four cynomolgus monkeys performing an oddball visual discrimination task. For juice reward, the subjects were required to release a lever rapidly in response to an infrequent (10-20% of trials) target cue (CS+) that was randomly intermixed with nontarget (CS-) stimuli presented on a video display. All LC neurons examined were phasically and selectively activated by target cues in this task. Other task events elicited no consistent response from these neurons (juice reward, lever release, fix-spot stimuli, nontarget stimuli). In one animal, nontarget cues phasically inhibited LC neurons. Phasic LC excitatory responses to target cues in this task occurred at a relatively short latency (mean = 90.7 msec), approximately 200 msec prior to the behavioral response (lever release). In addition, LC response magnitudes varied with behavioral performance, being substantially attenuated during epochs of poor performance (high false alarm rate). There was a positive correlation (r = 0.30, p 90 min), in parallel with a behavioral performance decrement. These results show that LC neurons are activated selectively by attended stimuli that demand a rapid response in this task, and that such LC responses may contribute to conditioned behavioral responses.

A Clinical Grading Scale to Predict Malignant Hyperthermia Susceptibility

Abstract: Background:The diagnosis of an acute malignant hyperthermia reaction by clinical criteria can be difficult because of the nonspecific nature and variable incidence of many of the clinical signs and laboratory findings. Development of a standardized means for estimating the qualitative likelihood of

Genetic and Structural Evidence for Antigen Selection of Anti-DNA Antibodies

Abstract: The primary structure of anti-DNA antibodies is highly diverse, a result of different germline variable (V) gene use, different combinations of immunoglobulin gene segments, peculiar heavy chain complementarity determining region 3 (H-CDR3) segments, and somatic mutations. Nevertheless, tertiary structure predictions reveal common features that yield information about likely contact sites in the anti-DNA combining site. That these contacts are involved with DNA binding is supported by recurrent features of a newly compiled set of homology groups of 13 variable regions of heavy chains (VH) and 11 variable regions of light chains (VL), characteristic pattern of somatic mutations, and the results of site-directed mutagenesis. The role of antigen in the etiology of the autoimmune response is viewed in light of recent data on overlaps between anti-DNA and anti-nucleic acid binding protein specificities.

The respective roles of perceived usefulness and perceived fun in the acceptance of microcomputer technology

Abstract: This study examined the effects of two main factors affecting microcomputer technology acceptance: perceived usefulness and perceived fun. We examined whether users are motivated to accept a new technology due to its usefulness or fun. Results of this study suggest that perceived usefulness is more influential than perceived fun in determining whether to accept or reject microcomputer technology. We also examined the impact of computer anxiety on acceptance. Results showed that computer anxiety had both direct and indirect effects on user acceptance of microcomputer technology, through perceived usefulness and fun. We also found attitude (satisfaction) to be less influential than perceived usefulness and fun. Implications for the design and acceptance of microcomputer technology and future research are discussed.

Global marital satisfaction versus marital adjustment: An empirical comparison of three measures.

Abstract: Two measures of marital satisfaction, the Quality of Marriage Index (R. Norton, 1983) and the Relationship Satisfaction Questionnaire (D. D. Burns & S. L. Sayers, 1992) were compared to a measure of marital adjustment, the Dyadic Adjustment Scale (G. B. Spanier, 1976). The measures showed excellent convergent validity (high correlations among each other and with other measures of marital functioning) and discriminant validity (low or nonsignificant correlations with psychopathology subscales). However, spouses' ratings of frequency of disagreements differed significantly from their ratings of satisfaction in the same areas. Formulas for converting scores among the measures are given, and the measures were found to have modest classification powers. The relative advantages and disadvantages of adjustment and satisfaction measures are discussed, and recommendations are made for when to use each type of measure

Vascular endothelial growth factor, platelet-derived growth factor, and insulin-like growth factor-1 promote rat aortic angiogenesis in vitro.

Abstract: The purpose of this study was to evaluate the vasoformative response of isolated vascular explants to a variety of growth factors that have been shown to stimulate angiogenesis. Rings of rat aorta were cultured in collagen gels under serum-free conditions in the presence or absence of vascular endothelial growth factor (VEGF), natural platelet-derived growth factor (PDGF), PDGF-AA, PDGF-BB, insulin-like growth factor-1 (IGF-1), transforming growth factor-alpha (TGF-alpha), transforming growth factor-beta 1 (TGF-beta 1), epidermal growth factor (EGF), interleukin-1 alpha (IL-1 alpha), or hepatocyte growth factor (HGF). The angiogenic response of the rat aorta was stimulated by VEGF, PDGF, PDGF-AA, PDGF-BB, and IGF-1. Maximum stimulatory effects were obtained with VEGF and PDGF-BB. By contrast, TGF-beta 1 and IL-1 alpha had inhibitory activity. No significant effects were observed with TGF-alpha, EGF, or HGF. The vascular outgrowth of VEGF-stimulated cultures was primarily composed of microvessels, whereas that of PDGF- and IGF-1-stimulated cultures contained an increased number of fibroblast-like cells. The inability of TGF-alpha, TGF-beta 1, IL-1 alpha, EGF, and HGF to stimulate rat aortic angiogenesis in serum-free culture suggests that either these factors require the mediatory activity of accessory cells that are not present in the rat aorta model or that blood vessels are heterogeneous in their capacity to respond to different angiogenic factors.

Work experiences, job involvement, and quality of work life among information systems personnel

Abstract: This study assesses the job involvement of 464 professionals and managers in the information systems (IS) field and investigates the role of involvement in influencing the quality of work life. Results show significant variation in the level of job involvement displayed by IS employees and differential patterns of relationships among the work variables for IS personnel with low, moderate, and high levels of job involvement. The findings indicate that involvement serves as a complex moderator role in the pattern of relationships of work experiences, and job characteristics with career expectations and career outcomes. It has both linear and non-linear relationships with sevearl of the study variables. While in some cases, high levels of job involvement tend to enhance the beneficial effects of work experiences on the quality of work life, in others such involvement tends to heighten the negative effects of role stressors. Implications of the findings and directions for future research are discussed.

Performance of Four Computer-Based Diagnostic Systems

Abstract: Background Computer-based diagnostic systems are available commercially, but there has been limited evaluation of their performance. We assessed the diagnostic capabilities of four internal medicine diagnostic systems: Dxplain, Iliad, Meditel, and QMR. Methods Ten expert clinicians created a set of 105 diagnostically challenging clinical case summaries involving actual patients. Clinical data were entered into each program with the vocabulary provided by the program's developer. Each of the systems produced a ranked list of possible diagnoses for each patient, as did the group of experts. We calculated scores on several performance measures for each computer program. Results No single computer program scored better than the others on all performance measures. Among all cases and all programs, the proportion of correct diagnoses ranged from 0.52 to 0.71, and the mean proportion of relevant diagnoses ranged from 0.19 to 0.37. On average, less than half the diagnoses on the experts' original list of reasonab...

Somatization in children and adolescents.

Abstract: Objective To review the empirical literature on somatization in the pediatric age group, emphasizing prevalence, influence on health care utilization, issues in the development of somatization, comorbidity with other psychiatric disorders, assessment, and treatment. Method One hundred nineteen studies and reports addressing medically unexplained somatic symptoms in children and adolescents were compiled via MEDLINE search and extensive cross-referencing. All available controlled studies were included, as were selected case reports and collections of cases. Selected citations from the adult literature were chosen for relevance to pediatric somatization. Results Recurrent, medically unexplained physical symptoms are common in the pediatric age group, are often associated with other psychiatric symptoms, and may represent a common presentation of psychiatric disorder in the primary care setting. DSM-III-R -defined somatization disorder is rare, and pseudoneurological symptoms are unusual. Patients may be at risk for potentially dangerous, costly, and unnecessary medical investigations and treatments, and they may excessively utilize health care services. Conclusion Our current understanding of pediatric somatization and its consequences is limited. Collaboration between mental health professionals and primary health care providers is essential. Consistent terminology, developmentally appropriate classification, and systematic future research will be necessary for the development of successful prevention and treatment strategies.

Revised Estimates of Diagnostic Test Sensitivity and Specificity in Suspected Biliary Tract Disease

Abstract: Background: The purpose of this study was to estimate the sensitivity and specificity of diagnostic tests for gallstones and acute cholecystitis. Methods: All English-language articles published from 1966 through 1992 about tests used in the diagnosis of biliary tract disease were identified through MEDLINE. From 1614 titles, 666 abstracts were examined and 322 articles were read to identify 61 articles with information about sensitivity and specificity. Application of exclusion criteria based on clinical and methodologic criteria left 30 articles for analysis. Cluster-sampling methods were adapted to obtain combined estimates of sensitivities and specificities. Adjustments were made to estimates that were biased because the gold standard was applied preferentially to patients with positive test results. Results: Ultrasound has the best unadjusted sensitivity (0.97; 95% confidence interval, 0.95 to 0.99) and specificity (0.95; 95% confidence interval, 0.88 to 1.00) for evaluating patients with suspected gallstones. Adjusted values are 0.84 (0.76 to 0.92) and 0.99 (0.97 to 1.00), respectively. Adjusted and unadjusted results for oral cholecystogram were lower. Radionuclide scanning has the best sensitivity (0.97; 95% confidence interval, 0.96 to 0.98) and specificity (0.90; 95% confidence interval, 0.86 to 0.95) for evaluating patients with suspected acute cholecystitis; test performance is unaffected by delayed imaging. Unadjusted sensitivity and specificity of ultrasound in evaluating patients with suspected acute cholecystitis are 0.94 (0.92 to 0.96) and 0.78 (0.61 to 0.96); adjusted values are 0.88 (0.74 to 1.00) and 0.80 (0.62 to 0.98). Conclusions: Ultrasound is superior to oral cholecystogram for diagnosing cholelithiasis, and radionuclide scanning is the test of choice for acute cholecystitis. However, sensitivities and specificities are somewhat lower than commonly reported. We recommend estimates that are midway between the adjusted and unadjusted values. (Arch Intern Med. 1994;154:2573-2581)

The influence of young age on outcome in early stage breast cancer

Abstract: Purpose: To assess the impact of young age on outcome in women with early stage breast cancer undergoing conservative surgery and radiation. Methods and Materials: Between 1981 and 1991, 980 patients with Stage I and II breast cancer underwent excisional biopsy, axillary dissection, and radiation. The median follow-up was 4.6 years, with a range of 1 month to 11 years. The patients were divided into three groups, based on age at the time of diagnosis: (a) age ≤ 35 years–64 patients, (b) age 36–50 years — 363 patients, and (c) age ≥ 50 years — 553 patients. The comparability of the groups was assessed in terms of clinical factors (tumor size and race), histopathologic factors (histologic subtype, final resection margin, estrogen and progesterone receptor status, pathologic nodal status), and treatment related factors (reexcision, median total dose to the primary, region(s) treated with radiation, and the use of adjuvant systemic chemotherapy and/or tamoxifen). Outcome was evaluated for overall, relapse-free, and cause-specific survival and patterns of first failure (breast, regional nodes, and distant metastasis). Results: There were no significant differences among the three groups in terms of race, clinical tumor size, pathology of the primary tumor., pathologic nodal status, final margin of resection, progesterone receptor status, median total dose to the primary humor, or the regions treated. However, younger women were significantly more likely to have estrogen receptor negative tumors, undergo reexcision, and receive adjuvant systemic chemotherapy without tamoxifen. Younger women were found to have a statistically significantly decreased 8-year actuarial relapse-free survival (53% vs. 67% vs. 74%, p = 0.009), cause-specific survival (73% vs. 84% vs. 90%, p = 0.02), freedom from distant metastasis (76% vs. 75% vs. 83%, p = 0.02), and a significantly increased risk of breast recurrence (24% vs. 14% vs. 12%, p = 0.001), and regional node recurrence (7% vs. 1% vs. 1%, p = 0.0002). The patients were further divided on the basis of their pathologic nodal status. There were no statistically significant differences among the three age groups for axillary node-positive patients for overall survival (75% vs. 80% vs. 74%), relapse-free survival (73% vs. 73% vs. 62%), cause-specific survival (76% vs. 85% vs. 80%), and freedom from distant metastasis (75% vs. 75% vs. 72%), or breast recurrence (0% vs. 9% vs. 6%). The findings were identical when the analysis was restricted to node-positive patients who received chemotherapy. However, for axillary node-negative women, young age was associated with a statistically significant decreased overall survival (71% vs. 83% vs. 92%), relapse-free survival,(51% vs. 65% vs. 76%), cause-specific survival (71% vs. 86% vs. 93%), freedom from distant metastasis (77% vs. 76% vs. 88%), and a statistically significant increased risk of breast recurrence (40% vs. 16% vs. 13%), and regional node recurrence (3% vs. 1% vs. 0%). The risk of a breast recurrence in axillary node-negative young women was decreased by the addition of adjuvant systemic chemotherapy but not by the use of reexcision. Conclusions: The present analysis demonstrates that young women with early stage breast cancer do significantly worse when compared to older women in terms of relapse-free survival, cause-specific survival, distant metastasis and breast and regional node recurrence. However, the adverse effect of young age on outcome appears to be limited to the node-negative patients. These findings suggest that node-negative early stage breast cancer in young women is a more aggressive disease, with an increased risk for all patterns of failure and a decreased survival.

An open trial of sertraline in personality disordered patients with impulsive aggression.

Abstract: The use of clozapine has been limited by the risk of agranulocytosis. The cumulative incidence of agranulocytosis is 0.80% after 1 year and 0.91% after 1 1/2 years. Risk is greatest during the first 3 months of treatment and greater among women and the elderly. White-cell counts tend to spike upward before the occurrence of agranulocytosis. The occurrence of a white-cell count spike of > or = 15% above the previous count predicts development of agranulocytosis within 75 days (risk ratio = 3.02; 95% confidence interval, 1.38-6.57). Our results indicate that hematologic monitoring is necessary and effective. They also suggest that the frequency of monitoring could be reduced after the initial period of maximal risk.

Evaluation of social problem solving in schizophrenia.

Abstract: We examined social problem solving in schizophrenia. Twenty-seven schizophrenic patients in an acute hospital, 19 patients with bipolar disease, and 17 demographically matched nonpatient controls were tested on an empirically developed problem-solving battery that assessed the ability to generate solutions to problems, the ability to evaluate the effectiveness of solutions, and the ability to implement solutions in a role-playing format. Schizophrenic Ss were impaired on all 3 problemsolving domains compared with the nonpatient controls, but bipolar Ss were equally impaired. Several alternative explanations for these findings were considered. The most compelling hypothesis is that the deficits resulted from different factors: cognitive impairment for schizophrenic Ss and acute illness for bipolar Ss. However, longitudinal studies are required to determine whether problemsolving deficits in schizophrenic patients persist during periods of remission. Implications for rehabilitation strategies are discussed. Impaired social functioning is one of the most fundamental and pernicious symptoms of schizophrenia . Deterioration of social relationships and increasing isolation are prominent premorbid markers (Strauss, Kokes, Klorman, & Sacksteder, 1977). An inability to navigate effectively in the social environment is a major factor in the poor quality of life experienced by most schizophrenic patients and is a significant source of stress that contributes to relapse (Falloon, Boyd, & McGill, 1984). Social withdrawal and an inability to fulfill social roles are magnified during prodromal periods and exacerbations, but these impairments frequently persist during periods of remission (Bellack, Morrison, Mueser, Wade, & Sayers, 1990). Social dysfunction often is found in patients without pronounced positive or negative symptoms (Bellack, Morrison, Wixted, & Mueser, 1990). It appears to be an independent aspect of the disorder (Strauss etal., 1977). The high prevalence and functional significance of social dys

Antiprotozoal activities of benzimidazoles and correlations with beta-tubulin sequence.

Abstract: Benzimidazoles have been widely used since the 1960s as anthelmintic agents in veterinary and human medicine and as antifungal agents in agriculture. More recently, selected benzimidazole derivatives were shown to be active in vitro against two protozoan parasites, Trichomonas vaginalis and Giardia lamblia, and clinical studies with AIDS patients have suggested that microsporidia are susceptible as well. Here, we first present in vitro susceptibility data for T. vaginalis and G. lamblia using an expanded set of benzimidazole derivatives. Both parasites were highly susceptible to four derivatives, including mebendazole, flubendazole, and fenbendazole (50% inhibitory concentrations of 0.005 to 0.16 microgram/ml). These derivatives also had lethal activity that was time dependent: 90% of T. vaginalis cells failed to recover following a 20-h exposure to mebendazole at 0.17 microgram/ml. G. lamblia, but not T. vaginalis, was highly susceptible to five additional derivatives. Next, we examined in vitro activity of benzimidazoles against additional protozoan parasites: little or no activity was observed against Entamoeba histolytica, Leishmania major, and Acanthamoeba polyphaga. Since the microtubule protein beta-tubulin has been identified as the benzimidazole target in helminths and fungi, potential correlations between benzimidazole activity and beta-tubulin sequence were examined. This analysis included partial sequences (residues 108 to 259) from the organisms mentioned above, as well as the microsporidia Encephalitozoon hellem and Encephalitozoon cuniculi and the sporozoan Cryptosporidium parvum. beta-tubulin residues Glu-198 and, in particular, Phe-200 are strong predictors of benzimidazole susceptibility; both are present in Encephalitozoon spp. but absent in C. parvum.

Involvement of D2 dopamine receptors in the nucleus accumbens in the opiate withdrawal syndrome.

Abstract: The nucleus accumbens is prominently implicated in the reinforcing effects of abused drugs, and is an important site for mediating aversive stimulus properties of opiate withdrawal. It is generally thought, however, that the role of the accumbens is negligible in the somatic signs of opiate withdrawal. Contrary to this assumption, we now report that D2 dopaminergic receptor activity in the accumbens area potently regulates somatic symptoms of opiate withdrawal. We find that activation of D2 receptors within the accumbens prevents somatic signs of naloxone-induced opiate withdrawal and, conversely, that blockade of accumbal D2 receptors in opiate-dependent animals elicits somatic withdrawal symptoms. These data indicate that dopamine in the accumbens not only is important in the rewarding effects of abused drugs, but also (via D2 receptors) plays a pivotal role in opiate withdrawal.

Simultaneous in vivo measurements of HbO2 saturation and PCr kinetics after exercise in normal humans

Abstract: Simultaneous measurements of phosphocreatine (PCr) and oxyhemoglobin (HbO2) saturation were made during recovery from exercise in calf muscles of five male subjects. PCr was measured using magnetic...

Epidemiology of Obstructive Sleep Apnea

Abstract: Sleep-disturbed breathing, which includes apneas, hypopneas, and oxygen desaturations, occurs in asymptomatic individuals and increases with age. Obstructive apnea is the most frequent type of respiratory disturbance documented by polysomonography, the gold standard test for assessing sleep-disturbed breathing. Many of the prevalence studies done to date have had one or more methodological weaknesses, including selection biases, varying definitions of obstructive sleep apnea, failure to distinguish types of apneas, failure to control for confounding variables, and small sample size. Although there is consensus on the definitions of sleep-disturbed breathing, the appropriate number of apneas and hypopneas for diagnosing clinically significant obstructive sleep apnea is uncertain. While the cutoff of five or more apneas and hypopneas per hour is historically considered abnormal, the origins of this number are vague, and the longevity of those who have this value on polysomnography is not necessarily reduced. This is particularly true among those without symptoms of obstructive sleep apnea syndrome, which include excessive daytime sleepiness, snoring, nocturnal awakenings, and morning headaches. Investigators should be careful to distinguish symptomatic study subjects from asymptomatic subjects, and to exclude central apneas in calculating their estimates. In addition, various studies have used different definitions of sleep apnea syndrome, making comparisons of point estimates difficult. It would be more appropriate for researchers to estimate morbidity and mortality indices with confidence intervals, using several different cutoff points. Subject selection in all studies should follow a two-stage sampling procedure. All subjects with symptoms compatible with obstructive sleep apnea syndrome and a subsample of asymptomatic individuals should be studied with all-night polysomnography. If portable monitoring is used, the validity and reproducibility of this diagnostic method should be assessed. Subjects with significant comorbidity should be excluded from prevalence studies. Factors that clearly increase the risk of sleep-disturbed breathing and obstructive sleep apnea and its related symptoms include age, structural abnormalities of the upper airway, sedatives and alcohol, and probably family history. Although endocrine changes such as growth hormone, thyroid hormone, and progesterone deficiency also have been suggested as risk factors for exacerbating obstructive sleep apnea syndrome, there is minimal epidemiologic evidence to support this. Case-control studies are recommended to assess the relation of endocrine factors to obstructive sleep apnea syndrome in a rigorous fashion. A limited number of mortality studies have suggested decreased survival in persons with the obstructive sleep apnea syndrome, possibly primarily due to vascular-related disease.(ABSTRACT TRUNCATED AT 400 WORDS)

A cell culture system for screening human serum for ability to promote cellular cholesterol efflux. Relations between serum components and efflux, esterification, and transfer.

Abstract: A cell culture system was employed to test a large number of samples of human serum for the ability to stimulate the efflux of cell cholesterol. The extent of efflux obtained with each specimen was correlated with the serum concentrations of cholesterol, triglycerides, apoprotein (apo) B, apo A-I, apo A-II, and lipoprotein subfractions (ie, high-density lipoprotein2 [HDL2], HDL3, lipoprotein [Lp] A-I, and LpA-I:A-II). In addition, the subsequent esterification of the released cholesterol and the distribution of the synthesized exogenous cholesteryl esters between HDL and low-density lipoprotein/very-low-density lipoprotein provided estimates of the lecithin:cholesterol acyltransferase (LCAT) and cholesteryl ester transfer protein (CETP) activities of each serum. The values for these activities were analyzed for correlations with cell efflux and the various serum parameters. Cell cholesterol efflux best correlated with serum total HDL cholesterol values. HDL2 and HDL3 correlated about equally well with efflux, whereas LpA-I demonstrated a much greater association with efflux than did LpA-I:A-II. Analysis of the data by partial correlation analysis indicated that HDL3 and LpA-I were the HDL subfractions most closely associated with efflux. Esterification of the released radiolabeled cholesterol was strongly and positively correlated with serum triglyceride concentrations and negatively related to the serum concentrations of HDL2. There was no relation between esterification values, which reflect LCAT activity, and efflux. The transfer of the labeled cholesteryl esters between HDL and apoB-containing lipoproteins was used as a measure of CETP activity and demonstrated a pattern in which all apoB-related parameters were positively correlated to transfer of esterified cholesterol, and all HDL associated parameters, particularly HDL3, were negatively related to transfer. No relations were observed between efflux, esterification, and transfer.

Strange attractors in brushless DC motors

Abstract: Deals with the open-loop dynamic characteristics of smooth-air-gap brushless DC motors. The steady-state characteristics of these systems, subject to constant input voltages and constant external torques, are formulated, whereby it is shown that the presence of viscous damping friction can cause the system to possess multiple physical equilibria. Furthermore, using an affine transformation, it is shown that the open-loop dynamics of smooth-air-gap brushless DC motors and the Lorenz system, a system known to possess chaotic behavior, are equivalent. Finally, computer simulations are presented that verify the existence of strange attractors in the open-loop dynamics of brushless DC motors. >

7 beta-hydroperoxycholest-5-en-3 beta-ol, a component of human atherosclerotic lesions, is the primary cytotoxin of oxidized human low density lipoprotein.

Abstract: Modification of low density lipoprotein (LDL) by free radical oxidation renders this molecular complex cytotoxic. Oxidized lipoproteins exist in vivo in atherosclerotic lesions and in the plasma of diabetic animals, suggesting that lipoprotein-induced tissue damage may occur in certain diseases. We undertook purification and identification of the major cytotoxin in oxidized LDL. The lipid extract from oxidized LDL was subjected to multiple HPLC separations, and the fractions were assayed for cytotoxicity. Mass spectrometry and nuclear magnetic resonance identified the purified toxin as 7 beta-hydroperoxycholest-5-en-3 beta-ol (7 beta-OOH-Chol). This molecule accounted for approximately 90% of the cytotoxicity of the lipids of oxidized LDL. We also found 7 beta-OOH-Chol in human atherosclerotic lesions from endarterectomy specimens obtained immediately after excision. These results are consistent with the hypothesis that the oxidized LDL present in lesions has the capacity to induce cell and tissue injury, leading to progression of the disease and the generation of the necrotic core of the lesion.

Does asymptomatic bacteriuria predict mortality and does antimicrobial treatment reduce mortality in elderly ambulatory women

Abstract: Objective: To determine whether asymptomatic bacteriuria in elderly ambulatory women is a marker of increased mortality and, if so, whether it is because of an association with other determinants o...