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Biomedical subjects

C Egan

Publications and source records attributed to C Egan.

At least 19 recordsLinked to original sources
PubMed2007

Acquired resistance to reoviral oncolysis in Ras-transformed fibrosarcoma cells.

Reovirus shows considerable potential as an oncolytic agent for Ras-activated tumors and is currently in clinical trials. Here we ask whether such tumor cell lines can acquire resistance to reoviral oncolysis. We challenged human HT1080 fibrosarcoma cells that carry a Ras mutation by prolonged exposure to reovirus, thereby yielding highly virus-resistant HTR1 cells. These cells are persistently infected with reovirus, exhibit high Ras activity and retain the original Ras gene mutation, showing that resistance to reovirus can be displayed in cells with active Ras. The HTR1 cells also exhibit reduced cellular cathepsin B activity, which normally contributes to viral entry and activation. Persistently infected HTR1 cells were not tumorigenic in vivo, whereas immunologically cured virus-free HTR1 cells were highly tumorigenic. Thus, acquisition of resistance to reovirus may constrain therapeutic strategies. To determine whether reoviral resistance is associated with a general reduction in apoptotic potential, we challenged the HTR1 cells with apoptotic inducers and E1B-defective adenovirus, resulting in significant apoptosis and cell death following both approaches. Therefore, even if resistance to reoviral oncolysis should arise in tumor cells in vivo, other therapeutic strategies may nevertheless remain effective.

Base Sequence↗
PubMed2006

Access to bone mineral density testing in patients at risk for osteoporosis.

INTRODUCTION: Prior studies have documented suboptimal diagnosis and treatment for osteoporosis in many settings. Consistent predictors of suboptimal management include patient age, physician training, and physician gender. We assessed whether access to bone mineral density (BMD) testing was a predictor of osteoporosis management in an at-risk population of patients from New Jersey. METHODS: Based on health care claims data, we identified three groups of at-risk beneficiaries, including women >or=65 (n=8,283), men and women >or=45 with a fracture (n=740), and men and women >or=45 taking chronic oral glucocorticoids (n=616). As the outcome of interest, we determined whether beneficiaries had undergone a BMD test and/or filled a prescription for a medicine used for osteoporosis (alendronate, calcitonin, hormone therapy, etidronate, risedronate, raloxifene, teriparatide) during the period 1 September 2002-31 August 2004. We assessed the relationship between this outcome and access to BMD testing. Access was characterized using two different measures: (1) the estimated driving time between each beneficiary's residence and the nearest BMD testing center ("driving time") and (2) the number of persons >or=65 years of age per BMD testing machine ("BMD scanner ratio") for each of the 21 counties in New Jersey. RESULTS: Of the 9,640 beneficiaries, we found that 3,104 (32%) had undergone a BMD test, 2,893 (30%) had filled a prescription for an osteoporosis medication, and 4,364 (45%) had one or both. Across the 21 counties of New Jersey, the percentage of at-risk patients who had a BMD test and/or medication for osteoporosis ranged from 38 to 52%. In models adjusted for patient factors and the clustering of patients in counties, driving time was not associated with patients being screened or treated for osteoporosis. The BMD scanner ratio was a weak predictor of osteoporosis management. CONCLUSION: Among beneficiaries of one large health insurer in New Jersey, two different measures of access to BMD testing were not important predictors of receiving testing and/or medications for osteoporosis.

Age Distribution↗
PubMed2006

The 5th International Conference on Basic and Therapeutic Aspects of Botulinum and Tetanus Neurotoxins. Workshop review: assays and detection.

The development of diagnostic tests for the botulinum neurotoxins is complicated by their extremely high potencies and the considerable diversity observed within the neurotoxin family. Current approaches for the detection of the toxins and the organism include amplified immunoassays and PCR techniques. Assays which exploit the biological activities within the botulinum toxins are also in development. These are based on both antibody and mass spectrometric techniques which measure the endopeptidase activities of the neurotoxins. This overview of the Assays and Detection Workshop of the 5th International Conference of on Basic and Therapeutic Aspects of Botulinum and Tetanus Neurotoxins discusses recent progress in the development of these assay systems and the issues that need to be overcome prior to their implementation.

Animals↗
PubMed2000

1-[4-(3-Phenylalkyl)phenyl]-2-aminopropanes as 5-HT(2A) partial agonists.

Phenylalkylamines such as 1-(4-bromo-2, 5-dimethoxyphenyl)-2-aminopropane (DOB; 1a) and its corresponding iodo derivative DOI (2) are commonly used 5-HT(2) serotonin agonists. Previous studies have established that the 2,5-dimethoxy substitution pattern found in these compounds is optimal for high affinity at 5-HT(2A) receptors and that substituents at the 4-position can modulate affinity over a wide range. We have previously shown, however, that when the 4-position is substituted with a 3-phenylpropyl substituent (i.e., 3), the compound binds with an affinity comparable to that of 1a but that it possesses 5-HT(2A) antagonist character. The present study examined the structure-affinity relationships of 3, and the results were very much unexpected. That is, the 2,5-dimethoxy substitution pattern of 3 is not required for high affinity. Either of the two methoxy groups can be removed without untoward effect on affinity, and relocation of the methoxy substituents actually enhances affinity by as much as an order of magnitude. None of the compounds displayed more than 20-fold selectivity for 5-HT(2A) over 5-HT(2C) receptors. In addition, several were demonstrated to act as 5-HT(2A) partial agonists. As such, the results of this study suggest that the structure-affinity relationships of phenylalkylamines as 5-HT(2A) ligands now be reinvestigated in greater detail.

3T3 Cells↗
PubMed2000

Binding of beta-carbolines and related agents at serotonin (5-HT(2) and 5-HT(1A)), dopamine (D(2)) and benzodiazepine receptors.

A large series of beta-carbolines was examined for their ability to bind at [3H]agonist-labeled 5-HT(2A) serotonin receptors. Selected beta-carbolines were also examined at 5-HT(2C) serotonin receptors, 5-HT(1A) serotonin receptors, dopamine D(2) receptors, and benzodiazepine receptors. Indolealkylamines and phenylisopropylamines were also evaluated in some of these binding assays. The beta-carbolines were found to bind with modest affinity at 5-HT(2A) receptors, and affinity was highly dependent upon the presence of ring substituents and ring saturation. The beta-carbolines displayed little to no affinity for 5-HT(1A) serotonin receptors, dopamine D(2) receptors and, with the exception of beta-CCM, for benzodiazepine receptors. Examples of beta-carbolines, indolealkylamines (i.e. N,N-dimethyltryptamine analogs), and phenylisopropylamines have been previously shown to produce common stimulus effects in animals trained to discriminate the phenylisopropylamine hallucinogen DOM (i.e. 1-(2, 5-dimethoxy-4-methylphenyl)-2-aminopropane) from vehicle. Although the only common receptor population that might account for this action is 5-HT(2A), on the basis of a lack of enhanced affinity for agonist-labeled 5-HT(2A) receptors, as well as on their lack of agonist action in the PI hydrolysis assay, it is difficult to conclude that the beta-carbolines behave in a manner consistent with that of other classical hallucinogens.

Animals↗
PubMed2000

Agonist high and low affinity state ratios predict drug intrinsic activity and a revised ternary complex mechanism at serotonin 5-HT(2A) and 5-HT(2C) receptors.

The ternary complex model as applied to G-protein coupled receptors (GPCR) predicts that an agonist binds with low affinity (K(L)) to the free receptor (R), leading to an agonist/receptor/G-protein complex. This ternary complex displays high agonist affinity (K(H)), resulting in signal transduction. Classical dogma states that the ratio K(L)/K(H) predicts intrinsic activity of drugs: the higher the ratio the higher the intrinsic activity. This model was based on studies in which K(L) and K(H) were indirectly determined by computer analyses of antagonist radioligand binding data. In order to investigate the relationship of K(L), K(H), and intrinsic activity for agonists at 5-HT(2A) and 5-HT(2C) receptors, we utilized (3)H-agonist and (3)H-antagonist radioligands to directly determine K(H) and K(L). Comparisons of the log K(L)/K(H) ratios and intrinsic activities of drugs for stimulating intracellular phosphatidylinositol (PI) hydrolysis revealed a strong correlation for 5-HT(2A) (r(2) = 0.92) and 5-HT(2C) (r(2) = 0.96) receptors. The data were fit to computer simulations based on the original ternary complex model and the revised ternary complex model in which an activated state of the receptor (R*) exists in equilibrium with the resting state of the receptor (R). Data produced for both 5-HT(2A) and 5-HT(2C) receptors were better-fitted to a revised ternary complex model, rather than the classical ternary complex model. These data support a revised model for the molecular events coupling GPCR to activation of G-proteins and indicate that a strong correlation between the K(L)/K(H) ratio and intrinsic activity for agonist action at GPCR is consistent with the existence of R*.

Animals↗
PubMed2000

Oestradiol decreases rat apolipoprotein AI transcription via promoter site B.

Oestrogens protect against ischaemic heart disease in the post-menopausal female by increasing serum concentrations of apolipoprotein (apo) AI and the abundance of high-density lipoprotein particles. In men and experimental male animals, the administration of oestrogen has variable effects on apo AI expression. As the major mode of oestrogen action on target genes involves regulating promoter activity and hence transcription, oestrogen is expected to alter transcription of the apo AI gene. To test this hypothesis, the effect of 17beta-oestradiol (E(2)), on rat apo AI promoter activity in male hepatoma HuH-7 cells, was tested by co-transfecting a reporter template, pAI.474.CAT containing-474 to-7 of the rat apo AI promoter and an oestrogen receptor (ER) expression vector, pCMV-ER. Transfected cells exposed to E(2) showed a dose-dependent decrease in chloramphenicol acetyltransferase (CAT)-activity, with a maximum 91+/-1.5% reduction at 1 microM E(2). Deletional analysis of the promoter localized the inhibitory effect of ER and E(2) to site B (-170 to-144) with an adjacent 5' contiguous motif, site S (-186 to-171) acting as an amplifier. HuH-7 cell nuclear extracts showed binding activities with both sites S and B, but recombinant human ER did not. Furthermore, nuclear extracts from E(2)-treated HuH-7 cells showed weaker binding activity to site B, but not to site S. In summary, the inhibitory effect of ER and E(2) on rat apo AI gene activity is mediated by a promoter element, site B. This inhibitory effect arises from a mechanism that does not involve direct ER binding to the B-element. The conclusion that E(2) inhibits apo AI transcription was confirmed in vivo. Treatment of male adult Sprague-Dawley rats with up to 200 microg E(2) for 7 days decreased apo AI protein and hepatic mRNA by 72+/-21% and 68+/-1.4% respectively. Results of 'run-on' transcription of the apo AI gene in isolated hepatic nuclei showed a 55% decrease in hormone-treated male rats. These findings suggest that E(2) exerts primarily an inhibitory effect within male hepatic nuclei.

Animals↗
PubMed1999

A randomized controlled trial of an enhanced patient compliance program for Helicobacter pylori therapy.

OBJECTIVES: To determine whether an enhanced compliance program (ECP) improves patient compliance with bismuth subsalicylate, metronidazole, and tetracycline hydrochloride (BMT) triple therapy for the treatment of Helicobacter pylori infection and to identify factors that affect compliance with therapy. DESIGN: A randomized controlled trial conducted in 4 staff-model health centers of a health maintenance organization in Massachusetts. PATIENTS AND METHODS: A total of 125 patients 18 years of age or older with peptic ulcer disease or dyspepsia whose clinicians prescribed BMT triple therapy for 14 days were randomized to a control group or to the ECP group. The ECP group received medication counseling (written and oral) from a pharmacist, along with a medication calendar and a minipillbox, as well as a follow-up telephone call after initiation of therapy. Compliance was assessed by a pill count, and factors affecting adherence to the regimen were identified by patients' reports. RESULTS: There was no statistically significant difference between the 2 groups in the number of patients taking more than 60% of the medications (89% of the control group vs 95% of the ECP group; P>.30). However, there was a statistically significant difference in the number of patients taking more than 90% of the medications (67% of the control group vs 89% of the ECP group; P<.01). An intention-to-treat analysis confirmed these results. The most frequently reported adverse effect was gastrointestinal intolerance. Other factors reported to affect compliance included the frequency of dosing and the number of pills. CONCLUSIONS: These findings suggest that although adverse effects were common, most patients were able to complete 60% or more of the 2-week regimen. An ECP further improved the percentage of medications taken.

Adult↗
PubMed1999

Activation of Src in human breast tumor cell lines: elevated levels of phosphotyrosine phosphatase activity that preferentially recognizes the Src carboxy terminal negative regulatory tyrosine 530.

Elevated levels of Src kinase activity have been reported in a number of human cancers, including colon and breast cancer. We have analysed four human breast tumor cell lines that exhibit high levels of Src kinase activity, and have determined that these cell lines also exhibit a high level of a phosphotyrosine phosphatase activity that recognizes the Src carboxy-terminal P-Tyr530 negative regulatory site. Total Src kinase activity in these cell lines is elevated as much as 30-fold over activity in normal control cells and specific activity is elevated as much as 5.6-fold. When the breast tumor cells were grown in the presence of the tyrosine phosphatase inhibitor vanadate, Src kinase activity was reduced in all four breast tumor cell lines, suggesting that Src was being activated by a phosphatase which could recognize the Tyr530 negative regulatory site. In fractionated cell extracts from the breast tumor cells, we found elevated levels of a membrane associated tyrosine phosphatase activity that preferentially dephosphorylated a Src family carboxy-terminal phosphopeptide containing the regulatory tyrosine 530 site. Src was hypophosphorylated in vivo at tyrosine 530 in at least two of the tumor cell lines, further suggesting that Src was being activated by a phosphatase in these cells. In preliminary immunoprecipitation and antibody depletion experiments, we were unable to correlate the major portion of this phosphatase activity with several known phosphatases.

Breast Neoplasms↗
PubMed1999

Major surgery suppresses maximal production of helper T-cell type 1 cytokines without potentiating the release of helper T-cell type 2 cytokines.

BACKGROUND: Major surgery is known to suppress T-cell function; however, its differential effects on the production of helper T-cell type 1 (T(H)1) and type 2 (T(H)2) cytokines remains unknown. OBJECTIVE: To measure the production patterns of T(H)1 (interleukin 2 [IL-2] and interferon gamma) and T(H)2 (IL-4 and IL-10) cytokines following major surgery. DESIGN, SETTING, AND PATIENTS: A cohort study of patients (both active and former members of the armed forces) at a military hospital. INTERVENTION: Aortic surgery or carotid endarterectomy and measurement of serum IL-6 levels by enzyme-linked immunosorbent assay. MAIN OUTCOME MEASURES: Unstimulated and stimulated intracellular levels of IL-2, IL-4, IL-10, and interferon gamma in CD4+, CD8+, and gammadelta+ T cells and serum IL-6 levels immediately before and for 2 days after aortic surgery or carotid endarterectomy. RESULTS: No unstimulated production of T(H) or T(H)2 cytokines was detected. Stimulated intracellular levels of IL-2 and interferon gamma were significantly depressed during the postoperative period in all T-cell subsets in both patient groups. There were no postoperative increases in stimulated IL-4 or IL-10 levels. CONCLUSION: Major surgery suppresses the potential responses of T(H)1 cytokines without enhancing production of T(H)2 cytokines.

Aged↗
PubMed1998

Creation of a constitutively activated state of the 5-HT2A receptor by site-directed mutagenesis: revelation of inverse agonist activity of antagonists.

Constitutively active GPCR have revealed novel properties of drugs that exhibit classical competitive antagonism at the native forms of GPCR. These drugs reverse basal levels of constitutive activity, indicating that they have inverse agonist activity. We were interested in determining if competitive antagonists of the native 5-HT2A receptor, in particular, antipsychotic drugs, exhibit inverse agonist activity at the constitutively active 5-HT2A receptor. All of the drugs tested reduced basal IP production of constitutively active 5-HT2A receptors, indicating that they all exhibited inverse agonist activity. Risperidone and ketanserin produced the greatest inhibition of basal IP production resulting in a reduction of basal activity in the C322K mutant receptor of 82% and 80%, respectively. Antipsychotic drugs display inverse agonist activity, indicating that stabilization of the inactive conformation of the 5-HT2A receptor may be a key component of their mechanism of action.

Amino Acid Substitution↗
PubMed1998

Points of view: Inuit women's perceptions of pollution.

Inuit women's perceptions of health risks from potential contamination in the arctic food chain were investigated in 1995 through in-depth interviews with 47 women in a Canadian arctic community. This number represents 34% of the eligible participants in the population of the research community. Many of these Inuit women suggest that pollution can appear in a variety of forms, from drug and alcohol consumption to visible air and water contaminants to possible invisible contaminants in arctic wildlife. Concepts of pollution--starting with the individual body and extending to the body politic--are influenced by a complex of sociocultural factors arising from historical and contemporary community life.

Attitude to Health↗
PubMed1997

Activating mutations of the serotonin 5-HT2C receptor.

Site-directed mutagenesis was performed to create a mutant serotonin 5-HT2C receptor that would mimic the active conformation of the native receptor. Structural alteration of receptor conformation was achieved by changing amino acid no. 312 from serine to phenylalanine (S312F) or lysine (S312K). After expression in COS-7 cells, the binding affinity of 5-HT for [3H]mesulergine-labeled 5-HT2C receptors increased from 203 nM (native) to 76 nM for S312F and 6.6 nM for S312K mutant receptors. 5-HT potency for stimulation of phosphatidylinositol (PI) hydrolysis increased from 70 nM (native) to 28 nM for S312F and 2.7 nM for S312K mutant receptors. The mutant receptors were constitutively active, stimulating PI hydrolysis in the absence of agonist. S312F and S312K mutations resulted in twofold and five-fold increases, respectively, in basal levels of PI hydrolysis. Mianserin and mesulergine displayed inverse agonist activity by decreasing basal levels of PI hydrolysis stimulated by S312K mutant receptors. [3H]5-HT and [3H]mesulergine labeled the same number of S312K mutant receptors and 5'-guanylylimidodiphosphate had no effect on [3H]5-HT binding. These results indicate that serine --> lysine mutation at amino acid no. 312 produces an agonist high-affinity state of the 5-HT2C receptor that spontaneously couples to G proteins and stimulates PI hydrolysis in the absence of agonist.

Animals↗
PubMed1992

Transmission of feline immunodeficiency virus from infected queens to kittens.

This study demonstrates the transmission of feline immunodeficiency virus (FIV) from infected queens to kittens in two separate litters. Queen 1 was infected by intravenous administration of FIV at 22 days prior to parturition. Two out of three kittens from the litter were found to be viremic at 10 weeks of age as detected by culture isolation and polymerase chain reaction detection of FIV DNA in peripheral blood mononuclear leukocytes. The third kitten remained aviremic through 40 weeks of age. Queen 2 was infected by subcutaneous administration of FIV 2 days prior to parturition. This litter also had two out of three kittens infected with FIV; however, viremia was not detected in one of the kittens until 21 weeks of age. Culture isolation was found to be superior to polymerase chain reaction for the early detection of FIV, and viremia was found to precede seroconversion by up to 4 weeks. Although all infected kittens have remained healthy, depressed CD4:CD8 lymphocyte ratios suggest that clinical disease may develop. This study suggests that FIV infection in cats may be a useful model system for the study of HIV transmission from mothers to infants.

Animals↗