Biomedical subjects

D W Taylor

Publications and source records attributed to D W Taylor.

At least 19 recordsLinked to original sources

PubMed2005

Blood-feeding in the young adult filarial worms Litomosoides sigmodontis.

In this study with the filarial model Litomosoides sigmodontis, we demonstrate that the worms ingest host red blood cells at a precise moment of their life-cycle, immediately after the fourth moult. The red blood cells (RBC) were identified microscopically in live worms immobilized in PBS at 4 degrees C, and their density assessed. Two hosts were used: Mongolian gerbils, where microfilaraemia is high, and susceptible BALB/c mice with lower microfilaraemia. Gerbils were studied at 12 time-points, between day 9 post-inoculation (the worms were young 4th stage larvae) and day 330 p.i. (worms were old adults). Only the very young adult filarial worms had red blood cells in their gut. Haematophagy was observed between days 25 and 56 p.i. and peaked between day 28 and day 30 p.i. in female worms. In males, haematophagy was less frequent and intense. Similar kinetics of haematophagy were found in BALB/c mice, but frequency and intensity tended to be lower. Haematophagy seems useful to optimize adult maturation. These observations suggest that haematophagy is an important step in the life-cycle of L. sigmodontis. This hitherto undescribed phenomenon might be characteristic of other filarial species including human parasites.

Age Factors↗

PubMed2005

Understanding Canadian student motivations and beliefs about giving blood.

BACKGROUND: A better understanding of Canadian blood donor beliefs and motivations is needed to develop targeted interventions. Recruiters must know how motivation variables and correlation patterns differ with donor experience and sex. STUDY DESIGN AND METHODS: Data addressing reasons for donating, statements about the blood supply, beliefs about donation consequences, and reasons for avoiding donation were collected from 450 undergraduates. Principal components analysis was used to investigate the underlying factorial structure of each domain. Men-women and donor-nondonor differences were explored with multivariate analysis of variance techniques. RESULTS: A bivariate model better represented donor beliefs than did a bipolar conceptualization. Negative beliefs distinguished donors and nondonors more so than did positive factors. Altruism dominated reasons for donating, whereas logistic factors accounted for the most variance in donation avoidance. Women were more concerned about adverse physical consequences, and nondonors expressed higher levels of groundless donation-related fears. CONCLUSION: Recruiters should consider the sex and donation experience of targets when they develop recruitment and retention strategies. Education programs aimed at overcoming fears and heightening awareness of need are recommended, as are operational improvements aimed at reducing barriers posed by time and inconvenience.

Adolescent↗

PubMed2003

Pre-exposure of cattle to drug-abbreviated Fasciola hepatica infections: the effect upon subsequent challenge infection and the early immune response.

In this study we examined whether juvenile liver flukes are capable of stimulating protective immune responses in cattle. Four experimental groups of cattle were studied as follows: group A, a positive control, received a primary infection on day 0 and a secondary infection 28 days later; group B also received two infections but the primary infection was terminated by drug treatment on day 5; group C, received infections on days 0, 5 and 10 which were terminated by drug treatments on days 1, 6 and 11 and then a secondary infection on day 28; group D received an infection only on day 28. Juvenile flukes appear to induce protective responses because: (a) group B animals had significantly lower levels of gamma-GT (P<0.05) than group D; (b) both groups B and C exhibited lower parenchymal phase GLDH levels (P=0.006 and 0.041, respectively); and (c) both groups B and C had lower secondary phase eosinophilia (P=0.002 and 0.02, respectively) than those in group D. Sera taken from groups A-C contained antibodies reacting to a variety of proteins in adult fluke somatic antigen and excretory-secretory preparations, particularly to proteins of 52-60, 68-72 and 82-96 kDa. After secondary challenge the antibody responses of group A to these proteins declined while reactivity to proteins of 28-30 kDa increased. Antibody responses to the 28-30 kDa proteins were not detected in groups B-D until 3 weeks later than those observed in group A. Antibody responses to Fasciola hepatica cathepsin L proteases, which are known to induce protection, were monophasic, of the IgG1 isotype only and were not observed prior to secondary challenge in any of the four groups. In contrast, the response to another protective antigen fraction, a high molecular sized haem protein, was of a mixed IgG1/IgG2 nature and was detected within 14 days of primary infection. However, no significant difference in antibody titres to either protein preparation was observed after the secondary infection when groups B and C were compared to group D.

Animals↗

PubMed2003

Analysis of pooled data from the randomised controlled trials of endarterectomy for symptomatic carotid stenosis.

BACKGROUND: Endarterectomy reduces risk of stroke in certain patients with recently symptomatic internal carotid stenosis. However, investigators have made different recommendations about the degree of stenosis above which surgery is effective, partly because of differences between trials in the methods of measurement of stenosis. To accurately assess the overall effect of surgery, and to increase power for secondary analyses, we pooled trial data and reassessed carotid angiograms. METHODS: We pooled data from the European Carotid Surgery Trial (ECST), North American Symptomatic Carotid Endarterectomy Trial, and Veterans Affairs trial 309 from the original electronic data files. Outcome events were re-defined, if necessary, to achieve comparability. Pre-randomisation carotid angiograms from ECST were re-measured by the method used in the other two trials. RESULTS: Risks of main outcomes in both treatment groups and effects of surgery did not differ between trials. Data for 6092 patients, with 35000 patient-years of follow-up, were therefore pooled. Surgery increased the 5-year risk of ipsilateral ischaemic stroke in patients with less than 30% stenosis (n=1746, absolute risk reduction -2.2%, p=0.05), had no effect in patients with 30-49% stenosis (1429, 3.2%, p=0.6), was of marginal benefit in those with 50-69% stenosis (1549, 4.6%, p=0.04), and was highly beneficial in those with 70% stenosis or greater without near-occlusion (1095, 16.0%, p<0.001). There was a trend towards benefit from surgery in patients with near-occlusion at 2 years' follow-up (262, 5.6%, p=0.19), but no benefit at 5 years (-1.7%, p=0.9). INTERPRETATION: Re-analysis of the trials with the same measurements and definitions yielded highly consistent results. Surgery is of some benefit for patients with 50-69% symptomatic stenosis, and highly beneficial for those with 70% symptomatic stenosis or greater but without near-occlusion. Benefit in patients with carotid near-occlusion is marginal in the short-term and uncertain in the long-term.

Aged↗

PubMed2003

The immune response of regional lymph nodes during the early stages of Fasciola hepatica infection in cattle.

In this study we examined regional immune responses to Fasciola hepatica infection in the natural ruminant host. Naïve cattle and those pre-exposed to a drug-abbreviated infection were subsequently challenged and lymph nodes extracted at slaughter. In vitro proliferation and cytokine production by mononuclear cells isolated from hepatic and mesenteric lymph nodes were measured after culture with whole fluke antigen (WFA). Hepatic lymph node cells had a significantly greater response to parasite antigen than mesenteric lymph node cells (P < 0.02), although there was no difference in the magnitude of the proliferative response between naïve and pre-exposed challenged cattle. Mononuclear cells from hepatic lymph nodes produced interferon gamma, interleukin 2 and interleukin 4 after culture with parasite antigen, indicative of a mixed, T helper type 0, response. Comparison of the hepatic node response to a variety of F. hepatica antigens showed that proliferation was lower after culture with cathepsin-L, than with a high molecular weight fraction, WFA or excretory-secretory antigen. Cell culture supernatant fluid from unstimulated hepatic lymph node cells showed an IgG1 response to antigens of 48, 52-70, 82, 96 and 120-190 kDa on Western blot in pre-exposed, but not naïve, challenged animals.

Animals↗

PubMed2001

Changes in properties of adenosine transporters in Trypanosoma evansi and modes of selection of resistance to the melaminophenyl arsenical drug, Mel Cy.

Resistance to arsenical drugs in trypanosomes has been linked to changes in adenosine uptake. The transport of melaminophenyl arsenicals into Trypanosoma brucei was shown to be mediated by an unusual adenosine nucleoside transporter, P2 (Carter and Fairlamb, 1993), and the loss of this transporter is associated with resistance to melaminophenyl arsenicals in these parasites. To further understand the mechanisms of arsenical resistance, we generated several lines of Mel Cy-resistant T. evansi from a drug-sensitive isolate using both in vivo and in vitro selection methods. Uptake of the melaminophenyl arsenical, Mel Cy on the P2 transporter was studied in the drug-sensitive as well as Mel Cy-resistant parasites, by means of inhibition of Mel Cy-induced lysis of trypanosomes, in an in vitro lysis assay. Adenosine uptake was also investigated using competition inhibition assays. Our study shows that T. evansi, TREU 1840, possesses the P1/P2 adenosine transport system as reported in T. brucei and T. equiperdum. However, in T. evansi, the P2 transporter is the larger transport process instead of the P1. The P2 transporter in T. evansi mediated the uptake of Mel Cy in the drug-sensitive parasites. The P2 was retained in all the arsenical-resistant T. evansi lines studied. However, the activity of the transporter was reduced to different extents in the different-resistant lines. The residual P2 activity related well to the levels of drug resistance in each line, suggesting that P2 activity could be an important marker for arsenical resistance. Furthermore, important differences were observed between the in vivo- and the in vitro-selected arsenical-resistant parasites suggesting that there may be differences in resistance phenotypes selected on the field.

Adenine↗

PubMed2001

Acquisition and decay of antibodies to pregnancy-associated variant antigens on the surface of Plasmodium falciparum-infected erythrocytes that protect against placental parasitemia.

Otherwise clinically immune women in areas endemic for malaria are highly susceptible to Plasmodium falciparum malaria during their first pregnancy. Pregnancy-associated malaria (PAM) is characterized by placental accumulation of infected erythrocytes that adhere to chondroitin sulfate A (CSA). Susceptibility to PAM decreases with increasing parity, apparently due to acquisition of antibodies directed against the variant surface antigens (VSAs) that mediate the adhesion to CSA (VSA(CSA)). This study found that levels of VSA(CSA)-specific antibodies depend on endemicity, that anti-VSA(CSA) IgG is acquired during gestation week 20, and that plasma levels of the antibodies decline during the postpartum period. There is evidence that VSA(CSA)-specific antibodies are linked to placental infection and that high antibody levels contribute to the control of placental infection by inhibiting parasite adhesion to CSA. Data suggest that VSA(CSA) is a target for vaccination against PAM.

Animals↗

PubMed2001

The three-dimensional structure of alpha-actinin obtained by cryoelectron microscopy suggests a model for Ca(2+)-dependent actin binding.

The three-dimensional structure of alpha-actinin from rabbit skeletal muscle was determined by cryoelectron microscopy in combination with homology modeling of the separate domain structures based on results previously determined by X-ray crystallography and nuclear magnetic resonance spectroscopy. alpha-Actinin was induced to form two-dimensional arrays on a positively charged lipid monolayer and micrographs were collected from unstained, frozen hydrated specimens at tilt angles from 0 degrees to 60 degrees. Interpretation of the 15 A-resolution three-dimensional structure was done by manually docking homologous models of the three key domains, actin-binding, three-helix motif and the C-terminal calmodulin-like domains. The initial model was refined quantitatively to improve its fit to the experimental reconstruction. The molecular model of alpha-actinin provides the first view of the overall structure of a complete actin cross-linking protein. The structure is characterized by close proximity of the C-terminal, calmodulin-like domain to the linker between the two calponin-homology domains that comprise the actin-binding domain. This location suggests a hypothesis to explain the involvement of the C-terminal domain in Ca(2+)-dependent actin binding of non-muscle isoforms.

Actinin↗

PubMed2001

Polymorphism of bovine major histocompatibility complex (MHC) class I genes revealed by polymerase chain reaction (PCR) and restriction enzyme analysis.

The polymorphic exon 2-exon 3 region of bovine major histocompatibility complex (MHC) class I genes was amplified by polymerase chain reaction (PCR) from genomic DNA samples with characterized class I polymorphism. The primers for amplification were designed in conserved regions at the borders of exons 2 and 3, based on all available cDNA sequences. The primers should, therefore, amplify most expressed class I genes, but may also amplify non-expressed class I genes. The PCR amplified class I gene fragments of 700 bp were characterized on the basis of restriction fragment length polymorphism (RFLP). The PCR-RFLP analysis of class I genes showed that the bands in each digestion could be classified as non-polymorphic, as shared between several bovine lymphocyte antigen (BoLA)-A types, or as specific to a single BoLA-A type. The same primers were then used for amplification of class I gene fragments from eight Sahiwal animals, a breed which originated in the Indian subcontinent. These studies showed that BoLA class I PCR-RFLP could be used to study class I polymorphism in family groups.

Animals↗

PubMed2001

Gravidity-dependent production of antibodies that inhibit binding of Plasmodium falciparum-infected erythrocytes to placental chondroitin sulfate proteoglycan during pregnancy.

During pregnancy, Plasmodium falciparum-infected erythrocytes sequester in the placenta by adhering to chondroitin 4-sulfate, creating a risk factor for both the mother and the fetus. The primigravidae are at higher risk for placental malaria than the multigravidae. This difference in susceptibility has been attributed to the lack of antibodies that block the adhesion of infected erythrocytes to placental chondroitin 4-sulfate in primigravid women. However, recent results show that many primigravidae at term have antibody levels similar to those of multigravidae, and thus the significance of antiadhesion antibodies in providing protection against malaria during pregnancy remains unclear. In this study, we analyzed plasma samples from women of various gravidities at different gestational stages for antiadhesion antibodies. The majority of women, regardless of gravidity, had similar levels of antibodies at term. Most primigravidae had low levels of or no antiadhesion antibodies prior to ~20 weeks of pregnancy and then produced antibodies. Multigravidae also lacked antibodies until ~12 weeks of pregnancy, but thereafter they efficiently produced antibodies. In pregnant women who had placental infection at term, higher levels of antiadhesion antibodies correlated with lower levels of placental parasitemia. The difference in kinetics of antibody production between primigravidae and multigravidae correlated with the prevalence of malaria in these groups, suggesting that antibodies are produced during pregnancy in response to placental infection. The early onset of efficient antibody response in multigravidae and the delayed production to antibodies in primigravidae appear to account for the gravidity-dependent differential susceptibilities of pregnant women to placental malaria.

Adult↗

PubMed2000

Isoforms of alpha-actinin from cardiac, smooth, and skeletal muscle form polar arrays of actin filaments.

We have used a positively charged lipid monolayer to form two-dimensional bundles of F-actin cross-linked by alpha-actinin to investigate the relative orientation of the actin filaments within them. This method prevents growth of the bundles perpendicular to the monolayer plane, thereby facilitating interpretation of the electron micrographs. Using alpha-actinin isoforms isolated from the three types of vertebrate muscle, i.e., cardiac, skeletal, and smooth, we have observed almost exclusively cross-linking between polar arrays of filaments, i.e., actin filaments with their plus ends oriented in the same direction. One type of bundle can be classified as an Archimedian spiral consisting of a single actin filament that spirals inward as the filament grows and the bundle is formed. These spirals have a consistent hand and grow to a limiting internal diameter of 0.4-0.7 microm, where the filaments appear to break and spiral formation ceases. These results, using isoforms usually characterized as cross-linkers of bipolar actin filament bundles, suggest that alpha-actinin is capable of cross-linking actin filaments in any orientation. Formation of specifically bipolar or polar filament arrays cross-linked by alpha-actinin may require additional factors that either determine the filament orientation or restrict the cross-linking capabilities of alpha-actinin.

Actin Cytoskeleton↗

PubMed2000

Clinical practice guidelines: the need for improved implementation strategies.

Although substantial resources have been spent developing clinical practice guidelines, little effort has been made to evaluate the effectiveness of their implementation. In the absence of effective implementation, CPGs will have minimal impact on changing behaviours. This article critically reviews the literature and identifies a number of reasons why these guidelines have not been implemented successfully. If CPGs are to have a positive impact upon clinical behaviour and practice, then more aggressive and positive implementation strategies are indicated. Five key ingredients for successful implementation of quality CPGs are identified and recommended.

Guideline Adherence↗

PubMed2000

Interleukin-5 is essential for vaccine-mediated immunity but not innate resistance to a filarial parasite.

The study of protective immune mechanisms effective against filarial nematodes has been hampered by the inability of these important human pathogens to infect laboratory mice. Recently, Litomosoides sigmodontis, a natural parasite of rats, has been developed as a valuable model for the study of filarial infection. BALB/c mice are fully susceptible to infection with L. sigmodontis third-stage larvae and develop patent infection. In contrast, mice on the C57BL background are resistant, and parasites undergo only a single molt and do not mature to adulthood. We used interleukin-5 (IL-5)-deficient mice on the C57BL/6 background to address the role of IL-5 and eosinophils in the innate resistance of C57BL/6 mice. We found no differences in parasite survival between IL-5-deficient and C57BL/6 mice. However, when these mice were used for the analysis of vaccine-mediated immunity, a critical role for IL-5 was elucidated. Mice genetically deficient in IL-5 were unable to generate a protective immune response when vaccinated with irradiated larvae, whereas C57BL/6 mice were fully protected from challenge infection. These studies help to clarify the highly controversial role of eosinophils in filarial infection.

Animals↗

PubMed2000

Characterization of conserved T- and B-cell epitopes in Plasmodium falciparum major merozoite surface protein 1.

Vaccines for P. falciparum will need to contain both T- and B-cell epitopes. Conserved epitopes are the most desirable, but they are often poorly immunogenic. The major merozoite surface protein 1 (MSP-1) is currently a leading vaccine candidate antigen. In this study, six peptides from conserved or partly conserved regions of MSP-1 were evaluated for immunogenicity in B10 congenic mice. Following immunization with the peptides, murine T cells were tested for the ability to proliferate in vitro and antibody responses to MSP-1 were evaluated in vivo. The results showed that one highly conserved sequence (MSP-1#1, VTHESYQELVKKLEALEDAV; located at amino acid positions 20 to 39) and one partly conserved sequence (MSP-1#23, GLFHKEKMILNEEEITTKGA; located at positions 44 to 63) contained both T- and B-cell epitopes. Immunization of mice with these peptides resulted in T-cell proliferation and enhanced production of antibody to MSP-1 upon exposure to merozoites. MSP-1#1 stimulated T-cell responses in three of the six strains of mice evaluated, whereas MSP-1#23 was immunogenic in only one strain. Immunization with the other four peptides resulted in T-cell responses to the peptides, but none of the resulting peptide-specific T cells recognized native MSP-1. These results demonstrate that two sequences located in the N terminus of MSP-1 can induce T- and B-cell responses following immunization in a murine model. Clearly, these sequences merit further consideration for inclusion in a vaccine for malaria.

Amino Acid Sequence↗

PubMed2000

Analysis of genes expressed at the infective larval stage validates utility of Litomosoides sigmodontis as a murine model for filarial vaccine development.

We used an expressed sequence tag approach to analyze genes expressed by the infective larvae of the rodent filarial parasite Litomosoides sigmodontis. One hundred fifty two new genes were identified, including several proposed as vaccine candidates in studies with human filarial parasites. Our findings have important implications for the use of L. sigmodontis as a model for filarial infection.

Amino Acid Sequence↗

PubMed1999

Structural studies of cytoskeletal protein arrays formed on lipid monolayers.

Lipid monolayers have been widely used for the production of 2-D crystalline arrays of water-soluble proteins for structural analysis. Less well known is the utility of lipid layers for the assembly of multicomponent structures in two dimensions. This report summarizes current efforts and limitations to utilize a monolayer system composed of the quaternary ammonium surfactant didodecyldimethyammonium and dilaurylphosphatidylcholine to assemble 2-D complexes between actin and cytoskeletal proteins.

Actinin↗

PubMed1999

Low-dose and high-dose acetylsalicylic acid for patients undergoing carotid endarterectomy: a randomised controlled trial. ASA and Carotid Endarterectomy (ACE) Trial Collaborators.

BACKGROUND: Endarterectomy benefits certain patients with carotid stenosis, but benefits are lessened by perioperative surgical risk. Acetylsalicylic acid lowers the risk of stroke in patients who have experienced transient ischaemic attack and stroke. We investigated appropriate doses and the role of acetylsalicylic acid in patients undergoing carotid endarterectomy. METHODS: In a randomised, double-blind, controlled trial, 2849 patients scheduled for endarterectomy were randomly assigned 81 mg (n=709), 325 mg (n=708), 650 mg (n=715), or 1300 mg (n=717) acetylsalicylic acid daily, started before surgery and continued for 3 months. We recorded occurrences of stroke, myocardial infarction, and death. We compared patients on the two higher doses of acetylsalicylic acid with patients on the two lower doses. FINDINGS: Surgery was cancelled in 45 patients, none were lost to follow-up by 30 days, and two were lost by 3 months. The combined rate of stroke, myocardial infarction, and death was lower in the low-dose groups than in the high-dose groups at 30 days (5.4 vs 7.0%, p=0.07) and at 3 months (6.2 vs 8.4%, p=0.03). In an efficacy analysis, which excluded patients taking 650 mg or more acetylsalicylic acid before randomisation, and patients randomised within 1 day of surgery, combined rates were 3.7% and 8.2%, respectively, at 30 days (p=0.002) and 4.2% and 10.0% at 3 months (p=0.0002). INTERPRETATION: The risk of stroke, myocardial infarction, and death within 30 days and 3 months of endarterectomy is lower for patients taking 81 mg or 325 mg acetylsalicylic acid daily than for those taking 650 mg or 1300 mg.

Aged↗

PubMed1999

Is there room for managed care in Canada? A preliminary inquiry of physicians.

Managed care, which is becoming increasingly prevalent in the United States, is virtually absent in Canada. Yet managed care, if implemented judiciously, has the potential to provide comprehensive, high quality care while containing spiraling healthcare expenditures. Managed care is also the foundation of integrated health systems, which have been widely discussed during the past few years. Then why has Canada been so slow to accept managed care? Since physicians have a great deal of influence on how healthcare is ultimately delivered, a group of Ontario physicians was surveyed to determine their perceptions of managed care. It was found that physicians were knowledgeable about the cost-containment capabilities of managed care but had misperceptions about managed care with respect to quality of patient care, preventive services and necessary medical care. Education and further research are recommended so that any debate about managed care, integrated systems or alternative physician payment can be meaningful, objective, beneficial and accurate.

Attitude of Health Personnel↗