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Biomedical subjects

C Doyle

Publications and source records attributed to C Doyle.

At least 73 records · Page 4Linked to original sources
PubMed1997

Nef proteins encoded by human and simian immunodeficiency viruses induce the accumulation of endosomes and lysosomes in human T cells.

The nef gene of human and simian immunodeficiency viruses encodes a 27-32-kDa myristoylated protein that is expressed at high levels early after infection. Many functions have been ascribed to the Nef protein, including the down-regulation of cell surface CD4 and a role in viral infectivity. This report describes a novel effect of the Nef protein on human T cells. Electron microscopy was used to examine human T cell lines stably expressing functionally active simian or human immunodeficiency virus type 1 Nef proteins. These studies revealed that the subcellular morphology of Nef-expressing cells was dramatically altered as compared with control cells. The Nef-expressing cells contained numerous membrane-bound vesicles prominently displayed throughout the cytoplasm. The vesicles were analyzed by immunoelectron microscopy (IEM) and by the accumulation of internalized nonspecific membrane tracer, and thus identified as late endosomes and lysosomes. The accumulation of endosomes and lysosomes in response to the expression of Nef was a consistent finding, observed with several different viral isolates and human T cell lines.

Antigens, CD↗
PubMed1997

Efficacy of psychosocial treatments for noisemaking in severe dementia.

Noisemaking is one of the most disturbing behavior disorders associated with dementia. Standard management practices, including pharmacological interventions, are not very successful in treating the behavior. Very little research has been carried out to evaluate innovative treatments or to determine the etiology of noisemaking. In this article, we report on a series of 12 case studies in which we tested the efficacy of some psychosocial interventions in reducing the frequency of noisemaking in long-term-care residents with severe dementia. Interventions were contingent reinforcement of quiet behavior and environmental stimulation tailored to individual preferences. Of the 12 patients recruited into the study, 2 died during the course of observations, 3 were not observed to be as noisy as reported by staff, and 3 showed a clear reduction in noise during the intervention period. Four patients did not show any overall reduction in noisemaking during psychosocial interventions. Future research could differentiate between types of interventions in successful cases and attempt to control further for the consistent application of interventions by long-term-care staff.

Aged↗
PubMed1997

Social-cognitive predictors of fruit and vegetable intake in children.

Social-cognitive theory (SCT) was used to explain the fruit and vegetable intake of 1,398 3rd graders. SCT variables assessed included self-efficacy, outcome expectations, preferences, social norms, asking skills, and knowledge. Fruit and vegetable intake was assessed with 7-day records. Bivariate correlations with fruit and vegetable intake ranged from .17 for asking skills to .29 for fruit and vegetable preferences. In analyses controlling for school-level clustering, only preferences and positive outcome expectations remained significantly associated with fruit and vegetable intake, accounting for approximately 10%-11% of the variance. Limitations in the conceptualization, scope, and measurement of the variables assessed may have contributed to the weak associations observed. Models incorporating factors other than individual-level social-cognitive variables may be required to more fully explain children's dietary behavior.

Child↗
PubMed1997

Patterns in children's fruit and vegetable consumption by meal and day of the week.

OBJECTIVE: To assess differences in children's consumption of fruit and vegetables (F&V) by day of the week and meal of the day. DESIGN: Baseline data from two school based nutrition education studies were combined for analysis. SUBJECTS/SETTING: 2984 third grade students from 48 participating elementary schools in three school districts in the metropolitan Atlanta area. MEASURES OF OUTCOME: The frequency of consumption of F&V abstracted by trained registered dietitians from prompted 7-day food records. STATISTICAL-ANALYSES PERFORMED: Mixed model analysis with meals and days as terms, controlling for the within school correlation, gender and ethnic group. RESULTS: F&V were most frequently consumed at weekday lunch, and second most frequently at dinner. Participation in school lunch accounted for a substantial proportion of F&Vs consumed at lunch. Few F&Vs were consumed at breakfast or snack. CONCLUSIONS: School lunch makes an important contribution to elementary school students' F&V consumption. Dietary change programs should target parents to increase F&V consumption at dinner, and target students for the meals over which they assert the most control: breakfast and snacks.

Adolescent↗
PubMed1997

Combined determination of Coxiella burnetii-specific immunoglobulin M (IgM) and IgA improves specificity in the diagnosis of acute Q fever.

Immunoglobulin M (IgM) and IgA responses in patients with acute Q fever were compared by enzyme-linked immunosorbent assay. An increase in both IgM and IgA was observed in paired sera from all 19 patients with acute Q fever, and both IgM and IgA levels showed good correlation with complement fixation test titers. Paired sera from 23 patients with infections other than Q fever were also tested. IgM levels were elevated in three of these patients, while IgA levels were elevated in three different patients (87% specificity for either IgM or IgA). As no patients in the disease control group showed elevated levels of both IgM and IgA, definition of a positive result as elevated levels of both IgM and IgA improved specificity to 100% without a decrease in sensitivity. This study indicates that detection of specific IgA is a useful adjunct to that of IgM in the diagnosis of acute Q fever.

Antibodies, Bacterial↗
PubMed1997

Resource implications of palliative chemotherapy for ovarian cancer.

PURPOSE: To describe the costs and outcomes of palliative chemotherapy in women with recurrent and refractory ovarian cancer from the perspective of a health care provider. PATIENTS AND METHODS: A retrospective study of 40 consecutive women who started second- or third-line chemotherapy for recurrent or refractory ovarian cancer between 1989 and 1992. Resource utilization from the commencement of second- or third-line chemotherapy until death or last follow-up evaluation was determined from a detailed chart review. All elements of care were recorded, including inpatient admissions, outpatient visits, chemotherapy drugs, nonchemotherapy drugs, radiation therapy, surgical procedures, investigations, and home care. Costs calculated using the hotel-approximation method are expressed in 1994 Canadian dollars. Actuarial estimates of cost and survival were used to account for censored observations. RESULTS: After a minimum follow-up period of 24 months, 36 of 40 women had died. The median survival duration of the group was 1.1 years from study entry and 1.7 years from first relapse. The women received a median of two regimens of chemotherapy (range, one to four) from study entry. They spent a median of 33 days as hospital inpatients (mean, 46; range, 0 to 185); 58% of these inpatient days were for symptomatic management and 32% were for chemotherapy. The mean cost per patient was $53,000 (median, $36,600; range, $4,800 to $162,900). The relationship between cost and survival duration was not linear--the cost per year was lowest for those who lived longest. Inpatient admissions, chemotherapy drugs, and outpatient visits accounted for 62%, 21%, and 8% of the total cost, respectively. The total costs attributable to chemotherapy were $24,000 (45% of total costs) and the total costs attributable to supportive care were $23,000 (43% of total costs). CONCLUSION: These data illustrate the cost of palliative management of recurrent and refractory ovarian cancer, which must be considered in the context of quality and duration of survival. They indicate the potential to improve cost efficiency by improving resource management, for example, by shifting from inpatient to outpatient chemotherapy, everything else being equal.

Adult↗
PubMed1996

Protective mucosal immunity elicited by targeted iliac lymph node immunization with a subunit SIV envelope and core vaccine in macaques.

Prevention of sexually transmitted HIV infection was investigated in macaques by immunization with a recombinant SIV (simian immunodeficiency virus) envelope gp 120 and core p27 vaccine. In two independent series of experiments, we used the novel targeted iliac lymph node (TILN) route of immunization, aiming close to the iliac lymph nodes draining the genitorectal mucosa. Rectal challenge with the SIVmac 32H J5 molecular clone in two series induced total protection in four out of seven macaques immunized by TILN, compared with infection in 13 of 14 unimmunized macaques or immunized by other routes (P = 0.025). The remaining three macaques showed either a decrease in viral load ( > 90%) or transient viremia, indicating that all seven TILN-immunized macaques showed total or partial protection (P = 0.001). Protection was associated with significant increase in the iliac lymph nodes of IgA antibody-secreting cells to p27 (P < 0.02), CD8-suppressor factor (P < 0.01), and the chemokines RANTES and MIP-1 beta (P < 0.01).

Animals↗
PubMed1996

The selective neuronal NO synthase inhibitor 7-nitro-indazole blocks both long-term potentiation and depotentiation of field EPSPs in rat hippocampal CA1 in vivo.

The membrane-permeant gas NO is a putative intercellular messenger that has been proposed on the basis of previous in vitro studies to be involved in synaptic plasticity, especially the induction of long-term potentiation (LTP) of excitatory synaptic transmission in the hippocampus and cortex. In the present study, the role of NO in synaptic plasticity has been investigated in vivo. In particular, the action of the novel and selective neuronal NO synthase (nNOS) inhibitor 7-nitro-indazole (7-NI) has been investigated on the induction of LTP and depotentiation (DP) of field EPSPs in CA1 of the hippocampus in vivo. Unlike previously studied nonselective NOS inhibitors, 7-NI does not increase arterial blood pressure. In vehicle-injected rats, high-frequency stimulation consisting of a series of trains at 200 Hz induced LTP. However, LTP induction was strongly inhibited in 7-NI (30 mg/kg, i.p.)-treated animals. The inhibitory effect of 7-NI on the induction of LTP was prevented by pretreatment with L-arginine, the substrate amino acid used by NOS. In control animals, low-frequency stimulation consisting of 900 stimuli at 10 Hz induced DP of previously established LTP, whereas in 7-HI-treated animals only a short-term depression was induced. This effect of 7-NI also was prevented by D-arginine. The LTP and DP induced in control animals in this study were NMDA receptor-dependent, the NMDA receptor antagonist 3-(R,S)-2-carboxypiperazin-4-yl-propyl-1- phosphonic acid inhibiting the induction of both forms of synaptic plasticity. The present experiments are the first to demonstrate that an NOS inhibitor blocks the induction of the synaptic component of LTP and DP in vivo and, therefore, these results strengthen evidence that the production of NO is necessary for the induction of LTP and DP.

Animals↗
PubMed1995

Attachment of an oligopeptide epitope to the C-terminus of recombinant SIV gp160 facilitates the construction of SMAA complexes while preserving CD4 binding.

A small 14 amino acid oligopeptide tag (termed SV5-Pk) was fused onto the carboxy-terminus of simian immunodeficiency virus gp160 expressed from a recombinant baculovirus. The presence of the Pk tag had no obvious effect on the expression and glycosylation of gp160 and did not interfere either with CD4 binding or with cleavage at its maturation site by the protease furin. The presence of the Pk tag did, however, facilitate the simplified purification of full-length gp160 and its incorporation into immunogenic solid matrix-antibody-antigen (SMAA) complexes.

Animals↗
PubMed1994

The protein tyrosine kinase p56lck regulates cell adhesion mediated by CD4 and major histocompatibility complex class II proteins.

The CD4 protein is expressed on a subset of human T lymphocytes that recognize antigen in the context of major histocompatibility complex (MHC) class II molecules. Using Chinese hamster ovary (CHO) cells expressing human CD4, we have previously demonstrated that the CD4 protein can mediate cell adhesion by direct interaction with MHC class II molecules. In T lymphocytes, CD4 can also function as a signaling molecule, presumably through its intracellular association with p56lck, a member of the src family of protein tyrosine kinases. In the present report, we show that p56lck can affect cell adhesion mediated by CD4 and MHC class II molecules. The expression of wild-type p56lck in CHO-CD4 cells augments the binding of MHC class II+ B cells, whereas the expression of a mutant p56lck protein with elevated tyrosine kinase activity results in decreased binding of MHC class II+ B cells. Using site-specific mutants of p56lck, we demonstrate that the both the enzymatic activity of p56lck and its association with CD4 are required for this effect on CD4/MHC class II adhesion. Further, the binding of MHC class II+ B cells induces CD4 at the cell surface to become organized into structures resembling adhesions-type junctions. Both wild-type and mutant forms of p56lck influence CD4-mediated adhesion by regulating the formation of these structures. The wild-type lck protein enhances CD4/MHC class II adhesion by augmenting the formation of CD4-associated adherens junctions whereas the elevated tyrosine kinase activity of the mutant p56lck decreases CD4-mediated cell adhesion by preventing the formation of these structures.

Animals↗
PubMed1994

The simian immunodeficiency virus Nef protein promotes degradation of CD4 in human T cells.

Expression of the Nef protein encoded by human and simian immunodeficiency viruses results in the specific down-regulation of CD4 from the cell surface in both lymphoid and non-lymphoid cells. In this report, we examine the biosynthesis and cell surface expression of CD4 in the human T cell line, CEM-SS, that has been stably transduced with the SIV nef gene. Quantification of CD4 in Nef-expressing cells reveals that the steady state level of CD4 is significantly reduced as compared to control transductants. The presence of Nef in these cells promotes the degradation of newly synthesized CD4 protein. The biosynthesis and oligosaccharide processing of CD4 in Nef-expressing T cells appears to be normal through the endoplasmic reticulum and Golgi compartments, suggesting that the degradation of CD4 is a late event in the biosynthetic pathway. Treatment with the lysosomotropic agents chloroquine and primaquine prevents the degradation of CD4 in Nef-expressing CEM-SS cells, indicating that the degradation of CD4 likely occurs in an acidic compartment. Thus the reduced cell surface expression observed in Nef-expressing CEM-SS cells is the likely consequence of a Nef-induced sorting of CD4 into a cellular compartment where CD4 is then degraded.

Biological Transport↗
PubMed1994

Site-directed mutagenesis of the ferric uptake regulation gene of Escherichia coli.

The 12 histidine and four cysteine residues of the Fur repressor of Escherichia coli were changed, respectively, to leucine and serine by site-directed mutagenesis of the fur gene. The affects of these mutations were measured in vivo by ligation of the mutated genes to a wild-type fur promoter followed by measurement of the ability of these plasmids to regulate expression of a lacZ fusion in the aerobactin operon. In vitro affects were assayed by insertion of the mutated genes in the expression vector pMON2064 attended by isolation of the altered Fur proteins and appraisal of their capacity to bind to operator DNA. The results suggest that cysteine residues at positions 92 and 95 are important for the activity of the Fur protein.

Bacterial Proteins↗
PubMed1994

Baboon and cotton-top tamarin B2m cDNA sequences and the evolution of primate beta 2-microglobulin.

Nonhuman primates represent phylogenetic intermediates for studying the divergence of human and murine beta 2Ms. We report the nucleotide sequences of B2m cDNA clones from a baboon cell line, 26CB-1 (Papio hamadryas; primates: Cercopithecoidea), and a cotton-top tamarin cell line, 1605L (Saguinus oedipus; primates: Ceboidea). The baboon and tamarin B2m sequences indicate a very slow rate of B2m evolution in primates relative to that in murid rodents. Phenotypic evolution of beta 2M has also been very conservative in primates, with only 9-14 substitutions separating baboon or tamarin beta 2Ms from those of humans or orangutans. Analyses of silent and amino-acid-altering nucleotide substitutions provide evidence that negative selection has acted to limit variability in beta strands of primate beta 2Ms, while positive selection has promoted diversity in non-beta-strand regions of murine beta 2Ms. No evidence for the action of selection upon beta 2M residues that contact the class I heavy chain was found in primates or mice. The finding that different selective forces have operated upon primate and murine beta 2Ms suggests that beta 2M may have evolved to serve distinct functions in primates and mice.

Amino Acid Sequence↗
PubMed1994

A survey of dementia in the Canberra population: experience with ICD-10 and DSM-III-R criteria.

A community survey of 1045 persons aged 70 years and over was conducted to identify cases of dementia in the cities of Canberra and Queanbeyan. Cases were identified using the Canberra Interview for the Elderly, administered by lay interviewers. When diagnostic criteria were rigidly applied, the point prevalence of dementia in the combined sample of community and institutional residents was considerably lower by ICD-10 than by DSM-III-R. Both criteria showed a similar rise in prevalence with age, and no gender difference. Agreement between the two systems had a kappa of only 0.48. 'Probable' cases by either criteria were identified solely from respondent-provided information in order to include persons for whom no informant was available. The point prevalence of such 'probable' cases was more similar for the two systems, and the kappa coefficient of agreement rose to 0.80. Analysis of the various components required for a diagnosis of dementia showed that the prevalence of all increased with age. Components involving cognitive assessment were correlated with education, but other components were not. The results of the study point to important differences between ICD-10 and DSM-III-R diagnoses of dementia.

Aged↗
PubMed1993

Cell adhesion mediated by CD4 and MHC class II proteins requires active cellular processes.

Human CD4 is an accessory molecule found on the cell surface of a subset of T lymphocytes. We have previously shown by infection of simian fibroblasts with an SV40-CD4 recombinant virus that CD4 acts as an adhesion molecule by binding to human MHC class II Ag expressed on the surface of human B lymphocytes. This report confirms that human B lymphoblastoid cell lines expressing class II molecules at the cell surface can bind to Chinese hamster ovary cells that have been stably transfected with human CD4. This cellular adhesion is a late event, which is first detected after 2 h, but remains stable for up to 16 h. The association between CD4 and class II is energy dependent, as it is detected at 37 degrees C, but not at 4 degrees C or if either cell type is fixed with paraformaldehyde. ATP is required for the establishment and maintenance of stable CD4/class II-mediated cell conjugates. Cytoskeletal interactions also regulate CD4/class II adhesion as treatment with the microtubule and microfilament inhibitors colchicine, cytochalasin-D, and nocodazole rapidly dissociates even preformed cell conjugates. Our observations also indicate that the Ag-independent engagement of class II by CD4 induces homotypic clustering of human B cells. This effect is blocked by reagents directed against lymphocyte function-associated Ag-1 and may result from the induction of a high affinity phenotype of lymphocyte function-associated Ag-1 induced by class II signaling. Finally, we discuss the implications of CD4/class II-mediated adhesion and the role of CD4 in the regulation of T cell adhesion.

Animals↗
PubMed1993

Interactions of CD4 with MHC class II molecules, T cell receptors and p56lck.

CD4 and CD8 are members of the immunoglobulin supergene family of proteins, and function as co-receptors with the T cell receptor (TCR) in binding MHC class II or class I molecules, respectively. Within this multimeric complex, CD4 interacts with three distinct ligands. CD4 interacts through its D1 and D2 domains with MHC class II proteins, through its D3 and D4 domains with T cell receptors, and through its cytoplasmic tail with p56lck, a src-related, protein tyrosine kinase. Each of these interactions is important in the function of CD4 and will be discussed in turn.

Amino Acid Sequence↗
PubMed1993

Downregulation of cell-surface CD4 expression by simian immunodeficiency virus Nef prevents viral super infection.

The nef gene product encoded by the mac239 proviral clone of simian immunodeficiency virus (SIV) markedly enhances viral replication and pathogenesis in vivo. We have used this biologically active nef isolate to examine the phenotype of Nef in retrovirally transduced human T cells in culture. SIV Nef is shown to dramatically inhibit cell-surface expression of the CD4 glycoprotein without significantly affecting the total steady-state level of cellular CD4. This downregulation of the cell-surface CD4 receptor for human immunodeficiency virus type 1 (HIV-1) infection correlated with the acquisition of resistance to superinfection by HIV-1. However, SIV Nef did not affect the level of gene expression directed by the HIV-1 long terminal repeat. It is hypothesized that downregulation of cell-surface CD4 by Nef facilitates the efficient release of infectious progeny virions and, hence, viral spread in vivo.

CD4 Antigens↗