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R Engler

Publications and source records attributed to R Engler.

At least 19 recordsLinked to original sources
PubMed2001

Absence of germline infection in male mice following intraventricular injection of adenovirus.

The possibility of inadvertent exposure of gonadal tissue to gene therapy vectors has raised safety concerns about germline infection. We show here that the receptor for coxsackie B viruses and adenoviruses 2 and 5 (CXADR) is expressed in mouse germ cells, suggesting the possibility that these viruses could infect germ cells. To directly assess the risk of germline infection in vivo, we injected an adenovirus carrying the germ-cell-specific protamine promoter fused to the bacterial lacZ reporter gene into the left ventricular cavity of mice and then monitored expression of the reporter gene in germ cells. To differentiate between infection of stem cells and differentiating spermatogenic cells, we analyzed expression of the reporter cassette at different times after viral delivery. Under all conditions tested, mice did not express the Escherichia coli beta-galactosidase protein in developing spermatids or in mature epididymal spermatozoa. Primary germ cells cultured in vitro were also refractory to adenoviral infection. Our data suggest that the chance of vertical germline transmission and insertional mutagenesis is highly unlikely following intracoronary adenoviral delivery.

Adenoviridae↗
PubMed1997

DNA scission after focal brain ischemia. Temporal differences in two species.

BACKGROUND AND PURPOSE: Species- and model-dependent differences in cell response to focal brain ischemia may underlie differences in adhesion receptor expression. The aim of this study was to quantitatively evaluate the spatial and temporal distribution of dUTP incorporation into damaged DNA, as an indicator of ischemic injury, in the corpus striatum. METHODS: Cerebral ischemia was produced in 16 nonhuman primates and 19 rats by occluding the middle cerebral artery (MCA:O) with reperfusion for various periods. In situ dUTP was incorporated into cells with DNA damage by terminal deoxynucleotidyl transferase (TdT), DNA polymerase I, or the Klenow fragment of DNA polymerase. Dual immunolabeling experiments with immunoprobes against neuronal, vascular, or glial marker proteins were performed. RESULTS: Significant topographical differences in dUTP between the two species were seen. In both models the TdT and polymerase I regions changed characteristically during focal ischemia. The number and density of dUTP-labeled cells increased with time from MCA:O and were dramatically different between the species (2P < .001). By 2 hours of ischemia, the density of dUTP label was 48.8 +/- 10.3 cells/mm2 in the primate and 2.4 +/- 0.8 cells/mm2 in the rat (2P < .05), but these values became nearly identical by 24 hours of reperfusion. In the primate, 80.0 +/- 6.6% of labeled cells displayed microtubule-associated protein-2 antigen (at 2-hour MCA:O), while 1.8 +/- 0.5% were associated with microvessels at 24 hours of reperfusion. CONCLUSIONS: In situ detection of DNA damage, accomplished by three methods, reveals distinct temporal, topographical, and density differences in ischemic injury to cells in the primate and the rat corpus striatum as a result of MCA:O.

Animals↗
PubMed1995

Comparative activity of peroxidase-antibody conjugates with periodate and glutaraldehyde coupling according to an enzyme immunoassay.

Horseradish peroxidase is often used as an antibody-coupled enzyme and several procedures have been developed to obtain IgG-peroxidase conjugates. The most widely used are coupling with periodate or glutaraldehyde. To compare the efficiency of these methods, the authors conducted periodate coupling or glutaraldehyde coupling in one or two steps, using the same batches of peroxidase, C-reactive protein (CRP) and anti-CRP monoclonal antibodies to develop a specially sensitive Elisa for CRP. Comparison of immunoenzymatic activities showed that periodate-mediated conjugation was much more efficient, because the activity of the coupling products was about 100 times greater than that of the products obtained after one or two-step conjugation with glutaraldehyde. The lower coupling efficiency observed with glutaraldehyde was not due to inactivation of the coupling agent or to a possible decrease in the affinity of the conjugates for CRP due to the coupling procedure. The differences in efficiency can be ascribed to the fact that periodate induced more coupling sites than glutaraldehyde. Periodate is therefore a better coupling agent for preparing conjugates to be used in Elisa or related techniques, in which conjugate size does not hinder accessibility to the antigen.

Antibodies, Monoclonal↗
PubMed1995

[Acute-phase proteins in inflammation].

The acute phase proteins (APPs) have been empirically defined as those whose plasma concentration changes following inflammatory reaction. Those proteins whose concentrations increase are referred to as positive APP, while those whose levels decline are termed negative APP. In man, positive APP are: alpha 1 acid glycoprotein, alpha 1 protease inhibitor, alpha 1 antichymotrypsin, haptoglobin, ceruloplasmin, fibrinogen, C-reactive protein, serum amyloid A. Great variability in the APP response between different species is observed. The principal functions of APP, result from the interaction of these proteins with ligands of various origins which give "protein-ligands" complexes. These complexes are cleared by the RES or by the hepatocyte. The results are protease inhibition, neutralization of toxic molecules such as hemoglobin or the superoxide anion, clearance of cell membranes and chromatin. The drop of the plasma concentration of negative APP during an inflammatory reaction carries a rise of free ligands (fatty acids, hormones, vitamins, trace elements). IL6 has been recognized as the principal regulator of most APP genes. The response of the hepatic cell to IL6 is characterized by the enhanced production of type 2 or IL6 specific APPs. The biochemical process of signal transduction is IL6--JAK2--APRF The set of APP genes regulated by IL1 type cytokines (type 1 APPs) is distinct from that regulated by IL6 type cytokine. IL1 and TNF alpha mediated stimulation of type 1 APP genes is synergistically enhanced by IL6 type cytokines. The biochemical process of signal transduction is IL1, IL6--Ras--MAP kinase--NFIL6 The targeted inflammatory proteic profile including the assay of C-reactive protein, haptoglobin and alpha 1 acid glycoprotein produces a "biological tool" to the clinician in order to manage an inflammatory response. IL6, a proteic marker for the future, connected with CRP, will be assayed during early inflammatory reaction.

Acute-Phase Proteins↗
PubMed1994

[Plasma concentration of C-reactive protein in patients with high estrogen levels].

The monitoring of inflammatory activity in patients with a high level of estrogen is controversial because the significance of a raised estradiol level on C-reactive protein (CRP) concentrations is a debated question. This prompted us to assay CRP by a sensitive Elisa in a sample of 30 patients with ovarian stimulation for in vitro fertilization, thus with high levels of estradiol. For 15 of these women, six to nine plasma samples were analyzed allowing a kinetic study of plasma levels of CRP, estradiol and sex steroid-binding plasma protein (SBP). No significant correlation was found between the concentrations of estradiol and CRP for the 30 patients. In the kinetic study, as mean estradiol levels rose exponentially from 50 to 1400 ng/l between day 5 and 14, the CRP level tended to vary markedly from one patient to another and sometimes from day to day, but there was never any relation with estradiol level. Furthermore, CRP did not significantly modify the slope of the regression line between estradiol concentration and the day of the menstrual cycle. In contrast, the effect of estradiol on SBP was clear, which supports the absence of estradiol effect on CRP level.

C-Reactive Protein↗
PubMed1993

Evaluation of the carcinogenic potential of pesticides. 4. Chloroalkylthiodicarboximide compounds with fungicidal activity.

The Health Effects Division of the Office of Pesticide Programs (OPP) assessed the carcinogenic potential of three structurally related chloroalkylthiodicarboximide fungicides using a consensus peer review process and EPA's 1986 guidelines for cancer risk assessment. All of the fungicides were categorized as Group B2 (probable human) carcinogens based upon findings of an increased incidence of malignant tumors, or combined malignant and benign tumors, in multiple experiments involving different strains of mice and rats. The primary sites of tumor formation with the chloroalkylthiodicarboximide fungicides in male and/or female mice (CD-1 and B6C3F1) were the gastrointestinal tract (captan, folpet, and captafol), the lymph system (folpet and captafol), and the vascular system (captafol). The main sites of tumor formation in rats of one or both sexes (CR CD, Wistar, or F344 strains) were the kidney (Captan and captafol), uterus (captan), mammary gland and liver (captafol). In addition, positive trends for thyroid, testicular, mammary gland, and lymph node tumors were observed with folpet in the same strains of rats. All three of the compounds exhibited positive mutagenic activity in a variety of in vitro short-term tests for gene mutation, DNA repair, and chromosomal aberrations in prokaryotic and eukaryotic cells, but were not genotoxic in available studies performed under in vivo conditions. The assessment of human cancer risk for captan, folpet, and captafol was made using low-dose extrapolation models.

Animals↗
PubMed1993

The prognostic utility of delayed-type hypersensitivity skin testing in the evaluation of HIV-infected patients. Military Medical Consortium for Applied Retroviral Research.

Many reagents and techniques have been used for delayed-type hypersensitivity (DTH) skin testing in the evaluation of HIV-infected patients, resulting in varied interpretation of the utility of DTH skin testing in this population. We report the development of a simple algorithm for selection of DTH antigens and the clinical relevance of DTH skin testing in HIV disease. Antigens and concentrations for testing were first evaluated in a demographically matched, HIV-negative, immunologically healthy population. The testing scheme was then applied to the HIV population of interest for 5 years at several clinical sites. The antigens and concentrations selected resulted in 100% reactivity to two or more antigens in the HIV-negative cohort. Anergy is thus a distinct immunologic abnormality. Although some correlation (r2 = 0.6) of skin test reactivity and CD4 cell count was found in a cohort of HIV-infected individuals, anergy was found to be independently predictive of the development of symptomatic late-stage disease (Walter Reed Stage 6), AIDS, or death. This stepwise evaluation of skin testing and reagents has led to the modification of the skin testing protocol by defining the minimum number of antigens required and establishing the independent prognostic role of DTH skin testing in the evaluation of HIV-infected patients. The addition of mumps (40 CFU/ml), tetanus (1:10), and candida (1:10) to the purified protein derivative (PPD) skin test provides the critical controls to evaluate the status of PPD skin test in HIV-infected individuals as well as to provide a useful and prognostic clinical immunology evaluation.

Adult↗
PubMed1992

Toxicological considerations for protein components of biological pesticide products.

The toxicity of protein components of microbial pesticide products is evaluated at EPA by requiring that pesticide manufacturers conduct a thorough taxonomic evaluation of the active microbial ingredient. The requirement for acute toxicity testing by dosing laboratory animals with the active microbial ingredient and with fermentation growth medium materials provides additional information on the toxicity of protein components of microbial pesticides. The potential for toxicity from proteins associated with contaminating organisms is addressed by use of appropriate quality control procedures to minimize or prevent growth of contaminants and by screening of fermentation batches for known human/mammalian pathogens. These considerations also would apply to any biochemical pesticide that is formed via the growth of a microorganism. If a protein itself is intended for commercial use as an active pesticide ingredient, acute exposure studies and in vitro digestibility studies could be done to answer potential concerns regarding toxicity.

Animals↗
PubMed1992

Cysteine and glycine supplementation modulate the metabolic response to tumor necrosis factor alpha in rats fed a low protein diet.

Responses to cytokines entail synthesis of substances rich in cysteine and glycine, such as glutathione (GSH), metallothionein and some plasma proteins. To examine the importance of an adequate supply of cysteine and glycine, we fed rats a low protein diet supplemented with L-cysteine and glycine, separately or in combination, or L-alanine, or a high protein diet for 1 wk before injection with tumor necrosis factor alpha (TNF) or saline. The high protein diet-fed group had greater liver weight and zinc and GSH concentrations after TNF than the group fed the low protein diet supplemented with alanine. Glycine and cysteine supplementation resulted in greater liver weight after TNF treatment than did alanine supplementation. Cysteine supplementation had a similar influence on GSH concentration. Ceruloplasmin, alpha-2-macroglobulin and alpha-1-acid glycoprotein were higher in TNF-treated rats than in saline controls in each dietary group. However, feeding supplementary glycine and cysteine and the high protein diet often resulted in different values than seen in animals fed the low protein diet supplemented with alanine. Paradoxically, lower ceruloplasmin concentrations were observed in animals fed the former diets than in those fed the latter. alpha-2-Macroglobulin concentration was lower in all animals fed low protein diets than in those fed the high protein diet. alpha-1-Acid glycoprotein was lowest in groups fed cysteine-supplemented diets and highest in the glycine-supplemented group.(ABSTRACT TRUNCATED AT 250 WORDS)

Alanine↗
PubMed1992

Anti-RNA polymerase I antibodies in the sera of MRL lupus mice at the initial stages of disease are directed primarily against phosphorylation-dependent epitopes.

Anti-RNA polymerase I (RPI) antibodies in the sera of MRL/Mp-lpr/lpr and MRL/Mp(-)+/+ mice, which develop an autoimmune disease similar to human systemic lupus erythematosus, were screened for reactivity with purified RPI or RPI which had been dephosphorylated. In every case (n = 10), dephosphorylation of RPI resulted in a significant decrease (33-95%) in antibody binding. The anti-RPI antibodies in the sera of the same mice approximately 6 weeks later also reacted better with untreated as compared to dephosphorylated RPI but, in every case, the decrease in antibody (0-30%) caused by dephosphorylation was substantially diminished. That the proportion of anti-RPI antibodies in the sera of MRL mice decreased with progression of lupus-like disease was confirmed by closely monitoring the antibodies over the course of disease. Anti-RPI antibodies produced at the earliest stages appeared to be directed almost exclusively against phosphorylation-dependent determinants since dephosphorylation of RPI essentially abolished antibody binding. Subsequently, the percentage of the total anti-RPI antibodies in the sera of these mice directed towards phosphorylation-independent epitopes increased linearly with time. The importance of phosphorylation-dependent epitopes on RPI for the development of the anti-RPI autoimmune response was supported by the observation that treatment of mice with alkaline phosphatase partially attenuated anti-RPI antibody production.

Animals↗
PubMed1991

Proclivity of activated neutrophils to cause postischemic cardiac dysfunction: participation in stunning?

Myocardial stunning is a reversible defect in contractile function provoked by brief episodes of ischemia followed by reperfusion. Many studies have demonstrated the potential involvement of free radicals in the etiology of myocardial stunning. While activated neutrophils have the capacity to release free radicals and evoke contractile dysfunction, it is not clear that this potential is realized in the absence of myocellular damage. Attempts to define the contribution of activated neutrophils to myocardial stunning by removing the cells from the bloodstream are contradictory, and the apparent simplicity of this seemingly logical approach is an illusion. For example, it is not known how many neutrophils are required to induce contractile failure, the site of action within the heart, the mechanisms that may be responsible, or even the time course or process of neutrophil activation. The production of free radicals and endothelial dysfunction may create conditions propitious for neutrophil recruitment. However, because activated neutrophils synthesize and release various mediators that are potentially toxic to myocardium, once the stage is reached for leukocyte accumulation, it may herald the progression from reversible to irreversible cardiac injury.

Animals↗
PubMed1991

Evaluation of the carcinogenic potential of pesticides. 3. Aliette.

Aliette, a fungicide compound, was evaluated for carcinogenic potential by the Health Effects Division of the Office of Pesticide Programs using a consensus peer review process and EPA's guidelines for risk assessment. Aliette was categorized as a group C (possible human) carcinogen based upon evidence of an increased incidence of combined benign and malignant urinary bladder tumors in a single study involving male Charles River (CR) CD rats. The bladder tumors occurred only at the unusually high top dose level of aliette that was tested (40,000/30,000 ppm). The compound was not carcinogenic in female CR-CD rats in the same study, or in CD-1 mice of either sex in a second study. Monosodium phosphite, the main urinary metabolite of aliette, was also not carcinogenic in male or female CR-CD rats. Aliette was not demonstrated to be genotoxic. No structural analogues of aliette were identified. The mechanism of action for the production of bladder tumors was not identified; however, it did not appear to involve a genotoxic effect, a carcinogenic effect of metabolites, or the formation of renal stones. The data were not found to be sufficient to quantify human cancer risk from aliette.

Adrenal Gland Neoplasms↗
PubMed1991

The weight of the evidence among group C carcinogens.

Pesticide chemicals (more than 40) with limited evidence for carcinogenicity in animal experiments, and assigned to Group C according to the EPA Guidelines for Carcinogen Risk Assessment, were further analyzed and ranked by refining the weight of the evidence evaluation. For some of these chemicals there were considerable concern with respect to their potential as human carcinogens and for others there was minimal concern. A clear tumor response at several doses, malignancy of the tumors, the tumor type (rare versus common), the timing of the tumor, and the observance of tumors in both sexes raised the concern for potential human carcinogenicity, as did ancillary information such as the structure-activity relationship and genotoxicity. The design and quality of the studies used in the evaluation were significant factors in reaching a conclusion concerning the carcinogenic potential of the chemicals. Potency factors (Q1*) calculated for these chemicals indicated no correlation with the level of biological evidence for carcinogenicity.

Animals↗
PubMed1990

Predicting 1-year outcome following acute myocardial infarction: physicians versus computers.

Whether decision rules derived statistically from patient data can produce better decisions than an expert clinician or a model of the expert clinician (expert system) is controversial. We examined this issue in the context of predicting cardiac death by 1 year for patients discharged from the hospital following acute myocardial infarction. Decision rules were derived from a base sample of 781 patients. These decision rules and three experienced cardiologists then estimated probability of death by 1 year for each patient in a separate test sample (n = 400). In our evaluation of the performance of the decision rules and physicians, we detected no differences, although the decision rules and physicians tended to classify the patients somewhat differently. Further multivariate analyses on the physicians' predictions showed that two of the physicians paid attention to somewhat different variables than the third physician. Lack of agreement among expert cardiologists would complicate modeling of a consensual decision-making process within the framework of an expert system.

Aged↗
PubMed1990

Evaluation of the carcinogenic potential of pesticides. 2. Methidathion.

The carcinogen potential of methidathion, a dimethoxyorganic phosphorus pesticide and cholinesterase inhibitor, was evaluated by the Health Effects Division of the Office of Pesticide Programs using a consensus peer review process and the EPA's guidelines for risk assessment. Methidathion was categorized as a Group C (possible human) carcinogen based upon evidence of an increased incidence of benign and malignant hepatocellular tumors, alone and in combination, in a single study involving male Chr-CD-1 mice. The compound was not carcinogenic in female Chr-CD-1 mice in the same study or in Sprague-Dawley rats of either sex in a second study. Methidathion was not genotoxic in a variety of in vitro or in vivo tests designed to detect DNA damage, chromosome aberrations, gene mutations, and sister chromatid exchange. Although methidathion was identified as being structurally similar to two other organophosphate insecticides, prothidathion and lythidathion, no toxicological data were available on either of these agents for comparative purposes. The biological information on methidathion was reviewed by the agency's FIFRA Scientific Advisory Panel who agreed with the category C designation for methidathion. The data were not found to be sufficient to quantify human risk to methidathion.

Adenoma↗
PubMed1990

"In vitro" digestion of intact bovine lens capsules by four human lysosomal cysteine-proteinases.

We have examined the biochemical degradation of an isolated basement membrane matrix (bovine lens capsule) by human liver cathepsins B, H and L and the cathepsin B-like proteinase from malignant ascitic fluid. This study was carried out using two different methods: The first strategy was to follow the liberation of soluble proteins and peptides as a function of time at different pHs. Then the digestion products were characterized, as collagen IV, fibronectin and laminin fragments, using monospecific polyclonal antibodies and a quantitative dot-blot analysis. From these results, the ability of the four proteinases to digest "in vitro" intact bovine lens capsule in the physiological pH range is demonstrated. Cathepsin L is the most powerful against the three membrane components studied. As shown by electroelution and immunochemical quantitation, the digestion would be a consequence of proteinases binding to the capsule. With intact basement membrane as a substrate a "in vitro" molecular analysis of this digestion process was possible by these methods. On this basis, the "in vivo" secretion of cysteine proteinases during malignancy would be related to the local basement membrane dissolution associated with tumor invasion.

Animals↗
PubMed1989

Evaluation of the carcinogenic potential of pesticides. 1. Acifluorfen.

The Health Effects Division of the Office of Pesticide Programs evaluates the carcinogenic properties of pesticides by a consensus peer review process in which all available biological information on a compound is evaluated according to EPA's guidelines for cancer risk assessment. In many cases, pesticides are also evaluated by an external group of accomplished scientists who comprise the Agency's Scientific Advisory Panel. The herbicide acifluorfen was evaluated by these processes and was classified as a Category B2 (probable human) carcinogen based upon evidence of an increased incidence of malignant, or combined benign and malignant, tumors in multiple experiments involving two different strains of mice. The compound produced benign and malignant liver tumors in male and female B6C3F1 mice and in female CD1 mice. Stomach papillomas were also observed in male and female B6C3F1 mice. Acifluorfen was mutagenic in bacteria and yeast, but not in mammalian cell systems. In addition, acifluorfen is structurally related to eight other diphenyl ether pesticides, all of which evoke liver tumours in mice or rats. The data were found to be sufficient to quantify human risk to acifluorfen.

Animals↗