Search PubMed⌕ Search

Biomedical subjects

D Stevenson

Publications and source records attributed to D Stevenson.

At least 55 records · Page 3Linked to original sources
PubMed1997

Mixed immunosorbent for selective on-line trace enrichment and liquid chromatography of phenylurea herbicides in environmental waters.

An immunosorbent containing antiisoproturon and antichlortoluron antibodies immobilised on aldehyde-activated silica was employed for the on-line preconcentration and liquid chromatography-diode array detection of several phenylureas. The efficiency of the coupling of the immunosorbent to the liquid chromatographic system and the characteristics of the immunosorbent were evaluated. The on-line system allowed the selective trace enrichment of chlortoluron, isoproturon, metobromuron, linuron and chlorbromuron at the 0.05-0.5 microgram l-1 level in ground and river waters and provided detection limits in the range 0.01-0.03 microgram l-1 by percolating only 10 ml of water sample. The proposed method was validated by analysing freeze-dried tap water samples with a high content in pesticides of different chemical functionalities. The results obtained were compared with the mean value obtained in an interlaboratory exercise.

Chromatography, Liquid↗
PubMed1997

Adenovirus infection of the cornea causes histopathologic changes in the lacrimal gland.

PURPOSE: To explore the effects on the lacrimal gland of adenovirus infection of the cornea. METHODS: Rabbit corneas were inoculated with human adenoviruses Ad5, Ad14, or a rabbit adapted form of Ad 5, and in some instances booster inoculations were given. Sections of lacrimal glands removed 21-59 days post-inoculation were immunostained using antibodies against rabbit Class I and Class II MHC molecules, CD4, CD8, CD18, and rabbit thymic lymphocyte antigen (RTLA). Relative numbers of positively stained cells were quantified with a Metamorph image analysis system. RESULTS: RTLA and CD18 antigens were expressed on many interstitial cells in the normal lacrimal gland, but few expressed CD4 or CD8. The number of RTLA+ cells increased by 60-100% after inoculation of Ad5 and after boosting, and CD18+ cells increased from 33-100% after inoculation of Ad5 and after boosting. Booster inoculations also caused focal lymphocytic infiltration. MHC Class I was expressed on interstitial cells and duct epithelium, but not acinar cells, and there was no detectable difference after viral infection. In controls, MHC Class II was localized to a population of interstitial cells and a few acinar cells. A single inoculation of the Ad5 virus did not result in an increase in the total number of MHC Class II-positive cells at 21 days, but inoculation with the rabbit-adapted Ad 5 and booster inoculations caused a 30% increase. CONCLUSIONS: Ad5 and rabbit-adapted Ad5 infection of the cornea induce lymphocytic infiltration in the lacrimal gland, and the effect is enhanced by boosting. There is also an increase in expression of MHC Class II after inoculation with rabbit-adapted Ad5 and with booster inoculations.

Adenoviridae↗
PubMed1996

Stereoselective metabolism of two keto-pyrrol analogues of 8-hydroxy-2-dipropyl-aminotetralin by freshly isolated rat hepatocytes.

In vitro metabolism models have been used to determine the relative metabolic stability of novel 2-aminotetralin analogues for the treatment of CNS diseases. Few of these new compounds had been produced as stereochemically pure materials and the achiral analytical techniques, used initially, measured the average metabolic clearance of the two enantiomers of the racemic mixtures. A chiral HPLC assay, using a Chiral AGP column, was developed for two of these racemic analogues and was used to measure the clearance of the enantiomers from suspensions of freshly isolated rat hepatocytes. Robust separations were obtained for both compounds and a number of metabolic products. The enantiomers of only one analogue were subject to different rates of metabolism. The extent of the difference was dependent upon the initial starting concentration of the incubation. The identity of certain metabolites was investigated using LC/MS. The enantio-selectivity appears to have arisen from the restricted hydroxylation of one analogue compared to that of the other.

8-Hydroxy-2-(di-n-propylamino)tetralin↗
PubMed1996

Evaluation of Cidofovir (HPMPC, GS-504) against adenovirus type 5 infection in vitro and in a New Zealand rabbit ocular model.

The antiviral inhibitory activity of Cidofovir [1-[(S)-3-hydroxy-2-(phosphonomethoxy)propyl]cytosine dihydrate, HPMPC, GS-504] against adenovirus type 5 (Ad5) in the New Zealand rabbit ocular replication model was evaluated. The 50% inhibitory dose (ID50) of Cidofovir was determined to be 4.7-9.5 micrograms/ml against four adenoviruses (two Ad5, Ad8 and Ad14) by plaque reduction assay in A549 cells. Twenty-four New Zealand rabbits received intrastromal inoculation and topical application of 2 x 10(6) plaque-forming units (PFU) per eye of Ad5 McEwen, a clinical isolate. Cidofovir was administered topically at three different concentrations twice per day, beginning 16 h postinoculation and continuing for 20 consecutive days. The inhibitory effects were determined by measuring suppression of virus replication and by observation of the clinical effects. Compared to the placebo group, the 1% and 0.5% Cidofovir-treated groups showed significantly reduced Ad5 ocular titers, fewer days of viral shedding and less severe subepithelial opacities (P = 0.0001). The 1% Cidofovir group had the lowest humoral antibody titer against adenovirus antigens, but the difference was not significant (P = 0.24). Cidofovir proved to have potent antiviral activity against adenovirus replication and may have great promise for the treatment of adenovirus infection. Further investigation is recommended.

Adenoviridae Infections↗
PubMed1996

Development of chiral high performance liquid chromatographic assays for the enantiomers of 8-hydroxy-(di-n-propylamino)tetralin and three 8-keto-pyrrole-substituted analogues.

Two chiral HPLC methods using protein-based stationary phases for the analysis of 8-hydroxy-(di-n-propylamino)tetralin and three 8-keto-pyrrole analogues are presented. Efficient solid-phase extraction enabled quantification of 0.02 microgram ml-1 of the 8-keto-pyrrole analogues from 500 microliters rat hepatocyte suspensions, and 0.2 microgram ml-1 to be measured from 50 microliters of rat plasma using UV detection at 315 nm.

8-Hydroxy-2-(di-n-propylamino)tetralin↗
PubMed1996

Development and evaluation of a chemiluminescent immunoassay for chlortoluron using a camera luminometer.

The feasibility of using an enhanced chemiluminescent immunoassay for screening water samples was adapted to a Dynatech Microlite camera luminometer and assessed to provide a semiquantitative assay based on a photographic record of the luminescent end-point. An enhanced chemiluminescent immunoassay of the herbicide chlortoluron was chosen in this instance as an example, although other pesticide compounds could equally well have been used provided that suitable antisera were available. This luminescent assay has shown considerable potential by providing a rapid, simple and portable means of monitoring multiple water samples for the presence of chlortoluron. The assay was able to identify samples containing the herbicide at or above the European limit for individual pesticides in drinking water [the EU Maximum Admissible Concentration (MAC) = 0.1 microgram l-1]. A 100% accuracy was obtained in the analysis of samples containing chlortoluron at concentrations above the range of 0.07-0.12 microgram l-1; however, for concentrations within this range the results were 65% accurate. Consequently, the method could greatly facilitate increased monitoring for the presence of chlortoluron in water supplies and in other areas of environmental analysis.

Environmental Monitoring↗
PubMed1996

Competitive enzyme-linked immunosorbent assay for the determination of the phenylurea herbicide chlortoluron in water and biological fluids.

A competitive ELISA method suitable for the monitoring of the herbicide chlortoluron [N-(3-chloro-4-methylphenyl)-N'-dimethylurea] in different types of water and biological fluids was developed. The production of the immunogen utilized in this work was achieved by covalently coupling bovine thryroglobulin with the synthesized hapten (N'-3-chloro-4-methylphenyl-N-carboxypropyl urea) using the N-hydroxysuccinimide active ester method. The chlortoluron antibody, raised in sheep after immunization with the immunogen, showed no cross-reactivity with a large range of pesticides, although some cross-reactivity was displayed with various phenylurea herbicides (i.e., chlorbromuron, isoproturon and metoxuron). The limit of detection of the chlortoluron ELISA method was 0.015 microgram l-1, well below the legal European limit for individual pesticides in drinking water (the EC maximum admissible concentration, 0.1 microgram l-1). In addition, reproducible and quantitative recovery of chlortoluron from water, obtained from various sources, and biological fluids was possible without any sample preparation. The ELISA technique for chlortoluron developed and described here proved to be rapid, sensitive and specific, fulfilling the needs of present legislation relating to the use and levels of pesticides in the environment.

Animals↗
PubMed1996

Phosphorylation and nuclear localization of the varicella-zoster virus gene 63 protein.

The protein encoded by varicella-zoster virus open reading frame 63 and carboxy-terminal deletions of the same were expressed either as fusion proteins at the carboxy terminus of the maltose-binding protein in Escherichia coli or independently in transfected mammalian cells. The truncations contained amino acids 1 to 142 (63 delta N) or 1 to 210 (63 delta K) of the complete 278-amino-acid primary sequence. Recombinant casein kinase II phosphorylated the 63F and 63 delta KF fusion proteins in vitro but did not phosphorylate the 63 delta NF fusion protein, implying that phosphorylation occurred between amino acids 142 and 210. Immunoprecipitation of 35S- or 32P-labelled extracts of cells transfected with plasmids expressing 63, 63 delta N, or 63 delta K also indicated that in situ phosphorylation most likely occurred between amino acids 142 and 210. These combined results suggest that casein kinase II plays a significant role in the phosphorylation of the varicella-zoster virus 63 protein. Indirect immunofluorescence of transfected cells indicated nuclear localization of the 63 protein and cytoplasmic localization of 63 delta K and 63 delta N, implying a requirement for sequences between amino acids 210 and 278 for efficient nuclear localization.

Amino Acid Sequence↗
PubMed1996

A high-involvement health care model.

Integrating a traditional approach into a high-involvement culture can result in successful redesign. Examples of successful redesign efforts as well as those that failed are discussed.

Decision Making, Organizational↗
PubMed1995

Outcome at 1-year adjusted age of 957 infants weighing more than 1250 grams with respiratory distress syndrome randomized to receive synthetic surfactant or air placebo. American and Canadian Exosurf Neonatal Study Groups.

This study determined outcomes at 12-months adjusted age of 957 infants weighing more than 1250 gm at birth who were subjects in a randomized, double-blind, controlled trial of synthetic surfactant or air placebo administered in a rescue trial at 23 hospitals in the United States and 13 hospitals in Canada. Follow-up results were available for 475 of 563 surviving infants who received air placebo (84%) and 482 of 571 infants who received synthetic surfactant (84%). Developmental outcome was equivalent in the two groups. Morbidity was less in the synthetic surfactant group as assessed by the need for medication for chronic lung disease (52 of 475 (11%) for the air placebo group vs 32 of 482 (7%) for the synthetic surfactant group) or respiratory support (10 of 475 (2%) for the air placebo group vs 1 of 482 (< 1%) for the synthetic surfactant group) at 1-year adjusted age. Bayley Scales of Infant Development (mental development Index: 102 for both the air placebo and synthetic surfactant groups; psychomotor development index: 95 for the air placebo group vs 94 for the synthetic surfactant group) and impairment rates (94 of 475 (20%) for the air placebo group vs 86 of 482 (18%) for the synthetic surfactant group) were similar in the two groups. Infants weighing more than 1250 gm who have respiratory distress syndrome have previously been shown to have improved survival rates and lower neonatal morbidity after treatment with synthetic surfactant. These follow-up data confirm that developmental outcome as determined at 12-months adjusted age is at least as good in those receiving synthetic surfactant.

Air↗
PubMed1995

Role of adenovirus type 5 early region 3 in the pathogenesis of ocular disease and cell culture infection.

Experimental animal virus replication models make it possible to study the role of viral gene products in adenovirus (Ad)-induced ocular disease. This study tested the hypothesis that the early region 3 (E3) of the human Ad genome plays an important role in the pathogenesis of Ad-induced ocular disease. Both Ad5 wt300, a genetically defined E3+ parent, and Ad5 dl327, a deletion mutant without E3 (E3-), replicated in ocular-derived cell cultures. Ad5 E3+ and Ad8 replicated more efficiently than did Ad5 E3- in cornea and conjunctival cell cultures. Lacrimal gland-derived cell cultures supported human Ad8 replication significantly more efficiently than did either Ad5 E3+ or Ad5 E3-. After intrastromal and topical inoculation of rabbits with either Ad wt300 or Ad dl327, a specific immune response was elicited that coincided with the appearance of subepithelial opacities that mimicked human disease both clinically and histologically. The clinical features (i.e., conjunctivitis, iritis, and corneal edema) were not significantly different for Ad5 E3(+)- and Ad5 E3(-)-induced ocular infection. Ad5 E3(+)- and Ad5 E3(-)-inoculated eyes shed virus for up to 7 and 5 days, respectively, and occasionally established persistent and/or latent infections in corneal, conjunctival, and, infrequently, lacrimal gland cells. Both Ad5 E3+ and Ad5 E3- spread from virus-inoculated animals to the cornea and conjunctiva of normal animals. Under current experimental conditions, expression of the E3 gene does not appear to affect the degree of virulence in ocular disease induced by Ad5 in the rabbit eye model. Deletion of the E3 gene from Ad5 does not make the model more like human disease.

Acute Disease↗
PubMed1995

Studies of adenovirus-induced eye disease in the rabbit model.

PURPOSE: To achieve a better understanding of the pathogenic processes associated with human adenovirus (Ad)-induced ocular disease. METHODS: Growth curves of Ad5 and Ad14 were performed in cell cultures derived from rabbit and human corneal epithelium (CE) and corneal keratocytes (CK). For in vivo studies, rabbit eyes were inoculated intrastromally and topically with 10(6) plaque-forming units per eye of Ad5 and ultraviolet light-inactivated (UV-1) Ad5 or Ad14, and the clinical features of the eyes were evaluated by biomicroscopic slit lamp examinations. Duration and quantitation of virus in tear samples were monitored. Humoral response was evaluated by enzyme-linked immunosorbent assay and serum neutralization titrations. Histopathologic and immunocytochemical staining of frozen corneal tissues was performed to determine the expression of major histocompatibility complex (MHC) class I and II and the presence of CD4+ and CD8+ T lymphocytes and CD18+ cells after the immunopathologic response elicited by virus inoculation. RESULTS: Both Ad5 and Ad14 replicated in all human cell cultures studied. In cells of rabbit origin, Ad5 replicated in cultured CE and CK cells, whereas Ad14 replication appeared restricted. Virus titers in ocular samples from Ad5-inoculated eyes peaked on postinoculation days 3 through 4, with approximately a 100-fold increase in infectious virus in comparison to initial titers. The duration of Ad5 shedding was 8.9 +/- 2.4 days. Ad5, Ad5 UV-I, and Ad14 induced seroconversion and subepithelial opacities. CD4+ and CD8+ T lymphocytes and CD18+ cells were present in these intrastromal immune cell infiltrates. Expression of MHC class I and II was observed in keratocytes and immune cells; MHC class I also was expressed on CE cells in inflamed areas. CONCLUSIONS: Ad5 is capable of replicating in both CE and CK cells of the rabbit eye. The presence of Ad antigens within the corneal stroma originating from infectious virus (Ad5), UV-inactivated virus (Ad5), or nonreplicating infectious virus (Ad14) can elicit indistinguishable immunopathologic responses in the stroma composed of CD4+, CD8+, and CD18+ cells.

Adenoviridae↗
PubMed1994

Development of an enzyme-linked immunosorbent assay for isoproturon in water.

A competitive enzyme-linked immunosorbent assay (ELISA) suitable for the determination of the urea herbicide isoproturon [3-(4-isopropylphenyl)-1,1-dimethyl urea] in water has been developed. A derivative of isoproturon [3-(4-isopropylphenyl)-1-carboxypropyl-1-methyl urea] has been synthesized and linked to thyroglobulin using the N-hydrosuccinimide reaction. The immunogen was used to immunize two sheep, which both responded by producing specific antibodies to isoproturon with little cross-reactivity to various structurally related and unrelated pesticides. The enzyme label was prepared by coupling the hapten to horseradish peroxidase using the above reaction. The coated-antibody competitive ELISA, which has a sensitivity of 0.03 microgram l-1, permits the direct determination of isoproturon in various water matrices and can facilitate the monitoring of water quality in drinking-water supplies.

Animals↗
PubMed1994

Delineation of a sequence required for nuclear localization of the protein encoded by varicella-zoster virus gene 61.

All characterized alphaherpesviruses encode a protein whose N-terminal region contains a novel zinc-binding motif, the C3HC4 domain. Homology between the different proteins is in general limited to key residues in this domain. In order to identify a separate landmark site in the C3HC4 protein encoded by varicella-zoster virus gene 61, namely the region required for nuclear localization, we have analysed a range of mutants in transient expression and immunofluorescence experiments. A basic region (RGAKRR) at residues 387 to 392 was found to be required for nuclear localization, and residues 390 and 391 were critical.

Amino Acid Sequence↗
PubMed1994

Characterization of the putative protein kinases specified by varicella-zoster virus genes 47 and 66.

The proteins predicted to be encoded by varicella-zoster virus (VZV) genes 47 and 66 display sequence similarity to the serine/threonine family of protein kinases. Homologues of gene 47 exist in alpha-, beta- and gamma-herpesviruses but homologues of gene 66 are specific to the alpha-herpesviruses. Monospecific rabbit antisera were raised against two separate fusion proteins constructed from a portion of each protein fused to the carboxy terminus of beta-galactosidase. These antisera were used to characterize the 47 and 66 proteins in VZV-infected cells and in cells infected with vaccinia virus recombinants expressing each protein. The 47 proteins is a 54K phosphoprotein which is distributed between the cytoplasmic and nuclear compartments of VZV-infected cells and is associated with the capsid/tegument fraction of purified VZV particles. Gene 66 encodes a 48K phosphoprotein when expressed by VZV or a vaccinia virus recombinant, and, in the latter case, the 66 protein was located exclusively in the cytoplasm. The 47 protein immunoprecipitated from VZV-infected cells could be phosphorylated in vitro, but the same protein produced by in vitro transcription and translation could not. This and other evidence indicates that additional proteins induced or encoded by VZV may be involved in the phosphorylation of the 47 protein.

Base Sequence↗
PubMed1994

Calcium ion and the membrane potential of tumor cells.

Calcium ion affects ion permeability and membrane potential among many other aspects of cell function. Initial effects of increasing extracellular calcium upon membrane potential were studied in a quail fibrosarcoma (QT35) where calcium had a dose dependent effect, and normal quail fibroblasts, where there was little effect. Comparisons were then made in six different human hepatocellular carcinomas (Tong, HepG2, Hep3B, PLC/PRF/5, Mahlavu, and HA22T) in response to smaller changes in concentration. There were insignificant changes in membrane potential in two cell lines and significant elevations in four. Cytolysis by natural killer cells also declined in rough proportion to the increase in membrane potential. The less differentiated hepatocellular carcinoma cells have both higher baseline membrane potentials and a greater potential increase to increased calcium. By contrast, more highly differentiated tumor cells had paradoxically smaller membrane potentials and along with normal cells had small potential responses to calcium increases.

Animals↗