Biomedical subjects

L Ryan

Publications and source records attributed to L Ryan.

At least 37 records · Page 2Linked to original sources

PubMed2001

Differential expression of Toll-like receptor 2 in human cells.

Human Toll-like receptor 2 (TLR2) is a receptor for a variety of microbial products and mediates activation signals in cells of the innate immune system. We have investigated expression and regulation of the TLR2 protein in human blood cells and tissues by using two anti-TLR2 mAbs. Only myelomonocytic cell lines expressed surface TLR2. In tonsils, lymph nodes, and appendices, activated B-cells in germinal centers expressed TLR2. In human blood, CD14+ monocytes expressed the highest level of TLR2 followed by CD15+ granulocytes, and CD19+ B-cells, CD3+ T-cells, and CD56+ NK cells did not express TLR2. The level of TLR2 on monocytes was after 20 h up-regulated by LPS, GM-CSF, IL-1, and IL-10 and down-regulated by IL-4, IFN-gamma, and TNF. On purified granulocytes, LPS, GM-CSF, and TNF down-regulated, and IL-10 modestly increased TLR2 expression after 2 h. These data suggest that TLR2 protein expression in innate immune cells is differentially regulated by inflammatory mediators.

Antibodies, Monoclonal↗

PubMed2000

The cytokine stimulating activity of (1-->3)-beta-D-glucans is dependent on the triple helix conformation.

The immunomodulating properties of comb-like branched (1-->3)-beta-D-glucans scleroglucan, schizophyllan and lentinan depend on branching pattern, molecular weight and higher-order structure. The effect of weight average molecular weight Mw and higher order structure of scleroglucan, on stimulation of human monocytes cultured in vitro to secrete tumor necrosis factor-alpha (TNF-alpha) was investigated. The higher order structures of the scleroglucan samples were determined by electron microscopy. The data showed that the samples with a linear wormlike, triple helical structure with Mw less than 50 x 10(4) g/mol or larger than 110 x 10(4) g/mol stimulated the monocytes more efficiently than samples with Mw in the range (67-110) x 10(4) g/mol. The denaturation of the linear triple helices by NaOH (> 0.25 M), followed by neutralization yielded blends of linear and macrocyclic topologies with concomitant irreversible reduction of the cytokine inducing activity compared with the untreated scleroglucans. The dose-dependent ability to activate monocytes to cytokine production was not restored following annealing of the denatured-renatured samples, despite the fact that electron micrographs revealed similar structures of these annealed samples to the starting material. Pre-incubation of monocytes with antibodies against cluster of differentiation antigens CD14 or CD11b reduced the scleroglucan potency to stimulate TNF-alpha secretion mainly for mAb against CD14 in the presence of serum.

Adjuvants, Immunologic↗

PubMed2000

Genetic susceptibility to benzene and shortened gestation: evidence of gene-environment interaction.

This study investigated whether the association between low level benzene exposure and shortened gestation is modified by two susceptibility genes, CYP1A1 and GSTT1. This report includes 542 (302 nonexposed, 240 benzene-exposed) nonsmoking and nondrinking mothers of singleton live births at Beijing Yanshan Petrochemical Corporation between June 1995 and June 1997. Epidemiologic and clinical data and blood samples were obtained from mothers. Multiple linear regression models were used to estimate the associations of benzene exposure and genetic susceptibility with gestational age, adjusting for maternal age, education, parity, stress, passive smoking, prepregnancy weight and height, and infant's sex. Without consideration of genotype, benzene exposure was associated with a decrease in mean gestational age of 0.29 (standard error (SE), 0.12) week. When stratified by the maternal CYP1A1 genotype, the estimated decrease was 0.54 (SE, 0.12) week for the AA group, which was significantly greater (p = 0.003) than that for the Aa/aa group, which showed no decrease in gestational age. When both CYP1A1 and GSTT1 were considered, the greatest decrease was found among exposed mothers with the CYP1A1 AA-GSTT1 absent group (0.79 (SE, 0.25) week) and the CYP1A1 AA-GSTT1 present group (0.50 (SE, 0.22) week). Among the nonexposed, genetic susceptibility alone did not confer a significant adverse effect. This study provides evidence of gene-environment interaction and supports further assessment of the role of genetic susceptibility in the evaluation of reproductive toxins.

Adult↗

PubMed2000

Human toll-like receptor 2 mediates monocyte activation by Listeria monocytogenes, but not by group B streptococci or lipopolysaccharide.

Human Toll like receptor (TLR) 2 has been implicated as a signaling receptor for LPS from Gram-negative bacteria and cell wall components from Gram-positive organisms. In this study, we investigated whether TLR2 can signal cell activation by the heat-killed group B streptococci type III (GBS) and Listeria monocytogenes (HKLM). HKLM, but not GBS, showed a time- and dose-dependent activation of Chinese hamster ovary cells transfected with human TLR2, as measured by translocation of NF-kappaB and induction of IL-6 production. A mAb recognizing a TLR2-associated epitope (TL2.1) was generated that inhibited IL-6 production from Chinese hamster ovary-TLR2 cells stimulated with HKLM or LPS. The TL2.1 mAb reduced HKLM-induced TNF production from human monocytes by 60%, whereas a CD14 mAb (3C10) reduced the TNF production by 30%. However, coadministrating TL2.1 and 3C10 inhibited the TNF response by 80%. In contrast to this, anti-CD14 blocked LPS-induced TNF production from monocytes, whereas anti-TLR2 showed no inhibition. Neither TL2.1 nor 3C10 affected GBS-induced TNF production. These results show that TLR2 can function as a signaling receptor for HKLM, possibly together with CD14, but that TLR2 is unlikely to be involved in cell activation by GBS. Furthermore, although LPS can activate transfected cell lines through TLR2, this receptor does not seem to be the main transducer of LPS activation of human monocytes. Thus, our data demonstrate the ability of TLR2 to distinguish between different pathogens.

Animals↗

PubMed2000

Intelligence and physical features of children of women with epilepsy.

The teratogenicity of maternal epilepsy has been attributed to several factors, including the antiepileptic drugs taken to prevent seizures during pregnancy, the occurrence of seizures during pregnancy, and the factors in the mother that caused her to have epilepsy. We have addressed the hypothesis that the children of women who have a history of epilepsy (seizure history), but who took no antiepileptic drugs (AED) and had no tonic-clonic seizures in pregnancy, have an increased risk of malformations and diminished intelligence. The frequency of cognitive dysfunction was determined in 57 seizure history and 57 matched control children aged 6-l6 years. The masked evaluation of the children included a physical and neurologic examination and testing with the Wechsler Intelligence Scale for Children-Revised (WISC-R) and a systematic physical examination for the features of the fetal AED syndrome. The evaluation of both parents of each child included a test of reasoning (Ravens Progressive Matrix) and a physical examination. There were no differences between the two groups of children in either IQ scores or physical features; none of the seizure history children was judged to have the "anticonvulsant face" or digit hypoplasia. This study had 80% power to rule out a difference of seven or more IQ points between the two groups, based on a two-sided test at a 5% level of significance. Our confidence in concluding that there was no difference between seizure history and control infants was strengthened by the fact that no statistically significant differences were observed with respect to multiple outcomes, including eight related measures of intelligence. Thirty (53%) of the seizure history mothers resumed taking AED after the birth of the child we evaluated. Additional studies are needed to address the teratogenicity of the antiepileptic drugs as monotherapy.

Adolescent↗

PubMed2000

Petrochemical exposure and menstrual disturbances.

BACKGROUND: An exploratory, cross-sectional retrospective study was conducted to examine the effects of benzene exposure on menstrual problems. METHODS: The study was based on a survey administered to over 3,000 women who worked in a large petrochemical company in Beijing, China. An abnormal menstrual cycle length (AMCL), defined as an average menstrual cycle length of greater than 35 days or less than 21 days, is the major outcome of interest. RESULTS: After 7 years of benzene exposure, the adjusted odds ratio of having AMCL for each additional 5 years of exposure was 1.71 (95% CI 1.27-2.31). Feeling stressed at work was also an important predictor. CONCLUSIONS: This study suggests a significant association of benzene exposure and perceived stress with menstrual disturbance. A prospective study is needed to confirm this finding.

Adult↗

PubMed2000

Multiple trace theory of human memory: computational, neuroimaging, and neuropsychological results.

Hippocampal-neocortical interactions in memory have typically been characterized within the "standard model" of memory consolidation. In this view, memory storage initially requires hippocampal linking of dispersed neocortical storage sites, but over time this need dissipates, and the hippocampal component is rendered unnecessary. This change in function over time is held to account for the retrograde amnesia (RA) gradients often seen in patients with hippocampal damage. Recent evidence, however, calls this standard model into question, and we have recently proposed a new approach, the "multiple memory trace" (MMT) theory. In this view, hippocampal ensembles are always involved in storage and retrieval of episodic information, but semantic (gist) information can be established in neocortex, and will survive damage to the hippocampal system if enough time has elapsed. This approach accounts more readily for the very long RA gradients often observed in amnesia. We report the results of analytic and connectionist simulations that demonstrate the feasibility of MMT. We also report a neuroimaging study showing that retrieval of very remote (25-year-old) memories elicits as much activation in hippocampus as retrieval of quite recent memories. Finally, we report new data from the study of patients with temporal lobe damage, using more sensitive measures than previously the case, showing that deficits in both episodic and spatial detail can be observed even for very remote memories. Overall, these findings indicate that the standard model of memory consolidation, which views the hippocampus as having only a temporary role in memory, is wrong. Instead, the data support the view that for episodic and spatial detail the hippocampal system is always necessary.

Epilepsy, Temporal Lobe↗

PubMed2000

The role of dietary fat in body fatness: evidence from a preliminary meta-analysis of ad libitum low-fat dietary intervention studies.

The role of high-fat diets in weight gain and obesity has been questioned because of inconsistent reports in the literature concerning the efficacy of ad libitum low-fat diets to reduce body weight. We conducted a meta-analysis of weight loss occurring on ad libitum low-fat diets in intervention trials, and analysed the relationship between initial body weight and weight loss. We selected controlled trials lasting more than 2 months comparing ad libitum low-fat diets with a control group consuming their habitual diet or a medium-fat diet ad libitum published from 1966 to 1998. Data were included from 16 trials with a duration of 2-12 months, involving 1728 individuals. No trials on obese subjects fulfilled the inclusion criteria. The weighted difference in weight loss between intervention and control groups was 2.55 kg (95% CI, 1.5-3.5; P < 0.0001). Weight loss was positively and independently related to pre-treatment body weight (r = 0.52, P < 0.05) and to reduction in the percentage of energy as fat (0.37 kg/%, P < 0.005) in unweighted analysis. Extrapolated to a BMI of about 30 kg/m2 and assuming a 10% reduction in dietary fat, the predicted weight loss would be 4.4 kg (95% CI, 2.0 to -6.8 kg). Because weight loss was not the primary aim in 12 of the 16 studies, it is unlikely that voluntary energy restriction contributed to the weight loss. Although there is no evidence that a high intake of simple sugars contributes to passive overconsumption, carbohydrate foods with a low glycaemic index may be more satiating and exert more beneficial effects on insulin resistance and cardiovascular risk factors. Moreover, an increase in protein content up to 25% of total energy may also contribute to reducing total energy intake. In conclusion, a low-fat diet, high in protein and fibre-rich carbohydrates, mainly from different vegetables, fruits and whole grains, is highly satiating for fewer calories than fatty foods. This diet composition provides good sources of vitamins, minerals, trace elements and fibre, and may have the most beneficial effect on blood lipids and blood-pressure levels. A reduction in dietary fat without restriction of total energy intake prevents weight gain in subjects of normal weight and produces a weight loss in overweight subjects, which is highly relevant for public health.

Body Mass Index↗

PubMed2000

Genetic control of susceptibility to infection with Mycobacterium tuberculosis in mice.

Genetic factors play a key role in host response, disease severity, and ultimate outcome of infection with Mycobacterium tuberculosis in humans. In the mouse, the DBA/2J strain is very susceptible to M. tuberculosis H37Rv infection, while the C57Bl/6J strain is resistant. In DBA/2J, a heavier bacterial burden causes a unique phenotype, that includes very severe and rapidly fatal pulmonary disease with extensive exudation of neutrophils and tissue necrosis, as opposed to slower progressive pulmonary disease characterized by the accumulation of epithelioid macrophages with protective immune and inflammatory responses in C57Bl/6J. To identify the genes responsible for differences in host response to M. tuberculosis in these two strains, 95 animals of an informative (C57Bl/6J x DBA/2J) F2 cross were infected intravenously with M. tuberculosis (1 x 10(5) CFU) and duration of survival was used as a quantitative phenotypic measure of susceptibility in a whole genome scan. Quantitative trait locus analysis (QTL) showed that the genetically controlled susceptibility was multigenic. QTL analysis identified two significant linkages on the distal portion of chromosome 1 (Trl-1, LOD, 4.80) and on the proximal portion of chromosome 7 (Trl-3, LOD, 4.66) that each account for approximately 21% of the phenotypic variance. A third suggestive linkage was identified on the proximal portion of chromosome 3 (Trl-2, LOD, 3.93; additional 18% of the variance). At each locus, homozygosity for the parental C57Bl/6J alleles was associated with increased resistance to infection. These novel mouse loci provide the basis for evaluating a possible association of the corresponding syntenic chromosomal regions in humans with susceptibility to tuberculosis.

Animals↗

PubMed2000

Hypertonic saline attenuates end-organ damage in an experimental model of acute pancreatitis.

BACKGROUND: Hypertonic saline (HTS) has been noted previously to reduce neutrophil activation. The aim of this study was to elucidate the effect of hypertonic resuscitation on the development of end-organ damage in an animal model of pancreatitis. METHODS: Pancreatitis was induced in Sprague-Dawley rats by intraperitoneal injection of 20 per cent L-arginine. Animals were randomized into four groups (each n = 8): controls; pancreatitis without intervention; pancreatitis plus intravenous resuscitation with normal saline (0.9 per cent sodium chloride 2 ml/kg) at 24 and 48 h; or HTS (7.5 per cent sodium chloride 2 ml/kg) at these time points. Pulmonary endothelial leakage was assessed by measurement of lung wet : dry ratios, bronchoalveolar lavage protein and myeloperoxidase activity. RESULTS: Animals that received HTS showed less pancreatic damage than those resuscitated with normal saline (1.0 versus 3.0; P = 0.04). Lung injury scores were also significantly diminished in the HTS group (1.0 versus 3.5; P = 0.03). Pulmonary neutrophil sequestration (myeloperoxidase activity 1.80 units/g) and increased endothelial permeability (bronchoalveolar lavage protein content 1287 microgram/ml) were evident in animals resuscitated with normal saline compared with HTS (1.22 units/g and 277 microgram/ml respectively; P < 0.02). CONCLUSION: HTS resuscitation results in a significant attenuation of end-organ injury following a systemic inflammatory response to severe pancreatitis.

Animals↗

PubMed2000

Molecular weight dependency on the production of the TNF stimulated by fractions of rye (1-->3),(1-->4)-beta-D-glucan.

Mixed-linkage (1-->3),(1-->4)-beta-D-glucan with a weight average molecular weight varying between 79,800 and 13,900 was purified from rye. These fractions were used for stimulation of human monocytes to produce tumour necrosis factor (TNF). A mixed-linkage beta-glucan with a weight average molecular weight of 18,900 was found to be the most potent immunostimulator.

Glucans↗

PubMed2000

Comparison of orbital colour Doppler findings with computed tomography angiography.

Colour Doppler imaging (CDI) of orbital vessels is noninvasive but may be fallacious, while computed tomography (CT) angiography displays a visual outline of orbital vessels. We compared clinical findings of the two methods in 33 patients with a wide variety of clinical conditions. It was not possible to visualize the central retinal arteries with CT angiography, but it was possible to show the intracranial carotid, which CDI could not. Changes in the ophthalmic arteries on CDI usually showed changes in calibre on CT angiography. Patients with unexplained or gross visual loss often showed marked abnormalities on CT scanning, not entirely consistent with the clinical picture. Several patients showed marked ectasia of the intracranial carotid along with variable clinical findings. Findings on CT angiography complement and augment those on CDI, and are likely to be more clinically valuable in the future.

Adult↗

PubMed2000

A scaled linear mixed model for multiple outcomes.

We propose a scaled linear mixed model to assess the effects of exposure and other covariates on multiple continuous outcomes. The most general form of the model allows a different exposure effect for each outcome. An important special case is a model that represents the exposure effects using a common global measure that can be characterized in terms of effect sizes. Correlations among different outcomes within the same subject are accommodated using random effects. We develop two approaches to model fitting, including the maximum likelihood method and the working parameter method. A key feature of both methods is that they can be easily implemented by repeatedly calling software for fitting standard linear mixed models, e.g., SAS PROC MIXED. Compared to the maximum likelihood method, the working parameter method is easier to implement and yields fully efficient estimators of the parameters of interest. We illustrate the proposed methods by analyzing data from a study of the effects of occupational pesticide exposure on semen quality in a cohort of Chinese men.

China↗

PubMed2000

Semiparametric regression analysis of interval-censored data.

We propose a semiparametric approach to the proportional hazards regression analysis of interval-censored data. An EM algorithm based on an approximate likelihood leads to an M-step that involves maximizing a standard Cox partial likelihood to estimate regression coefficients and then using the Breslow estimator for the unknown baseline hazards. The E-step takes a particularly simple form because all incomplete data appear as linear terms in the complete-data log likelihood. The algorithm of Turnbull (1976, Journal of the Royal Statistical Society, Series B 38, 290-295) is used to determine times at which the hazard can take positive mass. We found multiple imputation to yield an easily computed variance estimate that appears to be more reliable than asymptotic methods with small to moderately sized data sets. In the right-censored survival setting, the approach reduces to the standard Cox proportional hazards analysis, while the algorithm reduces to the one suggested by Clayton and Cuzick (1985, Applied Statistics 34, 148-156). The method is illustrated on data from the breast cancer cosmetics trial, previously analyzed by Finkelstein (1986, Biometrics 42, 845-854) and several subsequent authors.

Algorithms↗

PubMed2000

Involvement of CD14 and beta2-integrins in activating cells with soluble and particulate lipopolysaccharides and mannuronic acid polymers.

Lipopolysaccharide (LPS) and related bacterial products can be recognized by host inflammatory cells in a particulate, bacterium-bound form, as well as in various soluble, released forms. In the present study we have compared the mechanisms used by LPS, detoxified LPS (DLPS), and mannuronic acid polymers (M-polymers), in solution or covalently linked to particles, in stimulating monocytes to tumor necrosis factor (TNF) production. The addition of recombinant LPS binding protein (LBP) and/or soluble CD14 (sCD14) enhanced the production of TNF from monocytes stimulated with soluble LPS, DLPS, or M-polymer, but did not affect the response to M-polymer or DLPS attached to particles. Treatment of monocytes with antibody to CD14, CD18, or CD11b showed that CD14, but not CR3 (CD11b/CD18), mediated monocyte TNF production in response to the soluble antigens. In contrast, anti-CD14, anti-CD11b and anti-CD18 monoclonal antibodies all inhibited the response to the particulate stimuli. On the other hand, B975, a synthetic analog of Rhodobacter capsulatus lipid A, completely abrogated the monocyte TNF response induced by LPS but did not affect the TNF induction by DLPS or M-polymer, either in soluble or particulate forms. These data demonstrate that the engagement of immune receptors by bacterial products such as LPS, DLPS, and M-polymer is dependent upon the presentation form of their constituent carbohydrates, and that factors such as aggregation state, acylation, carbohydrate chain length, and solid versus liquid phase of bacterial ligands influence the mechanisms used by cells in mediating proinflammatory responses.

Acute-Phase Proteins↗

PubMed2000

Exposure to benzene, occupational stress, and reduced birth weight.

OBJECTIVES: The association between birth weight and exposure to benzene, work stress, and other occupational and environmental hazards was investigated. METHODS: In a large petrochemical industry, 792 pregnant workers were enrolled and followed up through delivery between May 1996 and December 1998. Exposure to benzene and other solvents was assessed by an industrial hygienist based on each woman's job title and workplace information. Other occupational and environmental exposures and personal information, including perceived work stress, exposure to noise, physical exertion at work, and passive smoking, were obtained by an interview questionnaire. Univariate and multivariate regression models were used to examine the individual and combined associations of occupational and environmental exposures with birth weight, with adjustment for major confounders including gestational age. RESULTS: In the univariate model, birth weight was negatively associated with exposure to benzene (-58 g (95% confidence interval (95% CI), -115 to -2)) and with work stress (-84 g (95% CI, -158 to -10)). In the multivariate model, there was a significant interaction between exposure to benzene and work stress relative to reduced birth weight, after adjustment for other environmental and occupational exposures and personal variables. Adjusted mean birth weight was 3445 g (95% CI 3401 to 3489) among those with neither exposure, 3430 g for those with exposure to benzene only, 3426 g for those with work stress only, and 3262 g (95% CI 3156 to 3369) for those with both exposures. In other words, there was 183 g (95% CI 65 to 301) reduction in birth weight among those with both exposure to benzene and work stress compared with those with neither exposure. Other work or environmental factors could not explain these findings. CONCLUSIONS: Low level exposure to benzene and work stress interact to reduce birth weight in this population.

Adult↗

PubMed2000

Analysis of dichotomous outcome data for community intervention studies.

Community intervention trials are becoming increasingly popular as a tool for evaluating the effectiveness of health education and intervention strategies. Typically, units such as households, schools, towns, counties, are randomized to receive either intervention or control, then outcomes are measured on individuals within each of the units of randomization. It is well recognized that the design and analysis of such studies must account for the clustering of subjects within the units of randomization. Furthermore, there are usually both subject level and cluster level covariates that must be considered in the modelling process. While suitable methods are available for continuous outcomes, data analysis is more complicated when dichotomous outcomes are measured on each subject. This paper will compare and contrast several of the available methods that can be applied in such settings, including random effects models, generalized estimating equations and methods based on the calculation of 'design effects', as implemented in the computer package SUDAAN. For completeness, the paper will also compare these methods of analysis with more simplistic approaches based on the summary statistics. All the methods will be applied to a case study based on an adolescent anti-smoking intervention in Australia. The paper concludes with some general discussion and recommendations for routine design and analysis.

Adolescent↗

PubMed2000

Adjuvant active specific immunotherapy for stage II and III colon cancer with an autologous tumor cell vaccine: Eastern Cooperative Oncology Group Study E5283.

PURPOSE: A randomized phase III clinical trial of adjuvant active specific immunotherapy (ASI) with an autologous tumor cell-bacillus Calmette-Guérin (BCG) vaccine was conducted to determine whether surgical resection plus ASI was more beneficial than resection alone in stage II and III colon cancer patients. PATIENTS AND METHODS: Patients (n = 412) with colon cancer (297 with stage II disease, 115 with stage III disease) were randomly allocated to an observation arm or to a treatment arm in which they received three weekly intradermal vaccine injections of 10(7) irradiated autologous tumor cells beginning approximately 4 weeks after surgery. The first two weekly injections also contained 10(7) BCG organisms. Patients were observed for determination of time to recurrence and disease-free and overall survival. RESULTS: This was a negative study in that after a 7.6-year median follow-up period, there were no statistically significant differences in clinical outcomes between the treatment arms. However, there were disease-free survival (P =.078) and overall survival (P =.12) trends in favor of ASI when treatment compliance was evaluated, ie, patients who received the intended treatment had a delayed cutaneous hypersensitivity (DCH) response to the third vaccination (induration >/=5 mm). Also, the magnitude of the DCH response correlated with improved prognosis. The 5-year survival proportion was 84.6% for those with indurations greater than 10 mm, compared with 45.0% for those with indurations less than 5 mm. CONCLUSIONS: When all randomized patients were evaluated, no significant clinical benefit was seen with ASI in surgically resected colon cancer patients with stage II or III colon cancer. However, there was an indication that treatment compliance with effective immunization results in disease-free and overall survival benefits.

Adjuvants, Immunologic↗