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Biomedical subjects

D W Taylor

Publications and source records attributed to D W Taylor.

At least 91 records · Page 5Linked to original sources
PubMed1990

Characterization of a Plasmodium falciparum epitope recognized by a monoclonal antibody with broad isolate and species specificity.

Monoclonal antibody (MAb) 7H8 raised against Plasmodium yoelii reacted with a series of proteins from P. falciparum that range in molecular weight from 46 to 194 kDa. By immunofluorescence assay, this MAb reacted with all isolates of P. falciparum tested. MAb 7H8 was used to screen a genomic expression library of asexual blood stage antigens of P. falciparum, Malayan Camp K+ and 7 independent clones were identified. These 7 clones were sequenced and the epitope recognized by MAb 7H8 in the recombinant protein of one of these clones was mapped. This epitope contained Lys Tyr Pro as core amino acids. However, similar sequences were not found in the other clones, indicating that this MAb binds to a structural epitope formed by different amino acids. The variable composition of the epitope may account for the number of P. falciparum malarial proteins recognized by MAb 7H8.

Amino Acid Sequence↗
PubMed1990

Immunological studies on onchocerciasis in Sierra Leone. 1. Pretreatment baseline data.

Cellular immune responses were tested in vitro using peripheral blood mononuclear cells from 203 individuals resident in an area of Sierra Leone where onchocerciasis is hyperendemic, and 32 individuals (Gambians) with no history of contact with Onchocerca volvulus. Mean reactivity to the mitogen, Concanavalin A, did not differ between these two groups, but responses to PPD were markedly lower in those with onchocerciasis. Proliferative responses to adult female O. volvulus antigen in the latter group were generally low although elevated reactivity was found in certain sub-groups. Higher responses were evident in infected 10-14 year olds, and there was an association between elevated reactivity to O. volvulus antigens and acute reactive dermatological signs, with individuals in the latter group also carrying higher dermal microfilarial loads. A sub-group presenting with lymphadenopathy showed the strongest associations of these three parameters. These results suggested the requirement for a threshold density of dermal microfilariae for induction of acute reactivity. The presence of immunosuppressive factors in soluble O. volvulus antigen was indicated by the ability to suppress, at low concentrations, the cellular responses to PPD of a proportion of individuals.

Adolescent↗
PubMed1990

Use of monoclonal antibodies for the characterization of Onchocerca volvulus antigens.

In order to identify Onchocerca volvulus antigens that could be considered as either diagnostic and/or immunoprophylactic, mouse monoclonal antibodies were produced against O. volvulus soluble antigens. Three were selected on the basis of their staining patterns in an indirect fluorescent antibody assay carried out on cryosections of adult O. volvulus. The first monoclonal antibody (K1-159) recognized a cuticular antigen which appeared in IFA to be restricted to the genus Onchocerca. However, neither Western blotting, nor the immunoprecipitation experiments performed on radiolabelled O. volvulus soluble antigen allowed detection of the corresponding antigen(s). The second monoclonal antibody (K1-126) bound to the muscle cells of adults. A 30,000 Mr antigen was detected by Western blot analysis of adult O. volvulus homogenate. This antigen was also recognised by sera from infected patients and corresponding antigenic determinants were detected in extracts of O. gutturosa, Acanthocheilonema viteae and Ascaris suum, but not in Brugia malayi. The third monoclonal antibody (K1-143) recognized egg shells and the surface of adult worms. The target epitope was not species specific and could be found in O. gutturosa, A. viteae, B. malayi and A. suum. The electrophoretic analysis of I-125 labelled soluble antigens and radiolabelled surface antigens of adult O. volvulus, showed numerous antigens (molecular weights ranging from 30,000 to 120,000 Mr) precipitated by K1-143. In an inhibition radioimmunoassay, K1-143 allowed the detection of corresponding antibodies in 79% of the O. volvulus patient sera tested.

Animals↗
PubMed1989

Purification and partial characterization of an unusual protein of Plasmodium falciparum: histidine-rich protein II.

The human malarial parasite Plasmodium falciparum secretes a histidine-rich protein (HRP-II) from infected erythrocytes. HRP-II has a very high content of histidine (H) (34%), alanine (A) (37%) and aspartic acid (D) (10%) and many contiguous repeats of the sequences AHH and AHHAAD. The histidine content of the protein suggested the potential to bind metal ions. We have demonstrated by metal chelate chromatography an extraordinary capacity of HRP-II to bind zinc ions (Zn2+) and employed this characteristic to isolate the extracellular protein. The HRP-II was further purified by antibody affinity chromatography. The identity of the purified protein was verified by relative molecular weight on denaturing polyacrylamide gels, by reactivity with monoclonal antibodies and monospecific rabbit antiserum, and by comparison of the amino-acid analysis with that derived from the cloned gene sequence. Analysis of the sequence for periodicities using the hydrophobic moment method indicated that HRP-II may potentially form a 3/10 helix. Immunoprecipitation of HRP-II from culture supernatants of parasites metabolically labeled with tritiated sugars showed that the extracellular form of HRP-II is a glycoprotein containing galactose.

Amino Acids↗
PubMed1989

The 86-kilodalton antigen from Schistosoma mansoni is a heat-shock protein homologous to yeast HSP-90.

We report the sequence of a cDNA clone encoding an 86-kDa polypeptide antigen (p86) from Schistosoma mansoni. Fusion proteins made in Escherichia coli are recognized by human infection sera. The reading frame of this antigen is highly homologous to those of the large heat-shock proteins of Saccharomyces cerevisiae (HSP90) and Drosophila melanogaster (HSP83). mRNA encoding p86 increases in response to heat shock of adult worms, as does HSP70. Comparisons of the sequences of HSP70 and HSP83 homologues show that these two families of heat-shock proteins are not significantly related except for the last four amino acid residues, which are Glu-Glu-Val-Asp in every case. This sequence is not found at the carboxy terminus of any other protein in the current databases.

Amino Acid Sequence↗
PubMed1989

Smoking cessation in primary care. A randomized controlled trial of nicotine-bearing chewing gum.

The results are reported from a multicentered, randomized clinical trial of a physician-delivered smoking cessation intervention package. All physicians attended a four-hour training session during which the rationales for the different aspects of the intervention were discussed, including a detailed description of the proper use of nicotine-bearing chewing gum. Patients were randomized to receive an offer of a prescription of 2 mg of nicotine chewing gum in addition to the basic intervention (n = 111) or the basic intervention alone (n = 112). The basic intervention included advice, setting a date for quitting, self-help materials, and the offer of supportive follow-up visits. Receptionists were instructed to recruit the first two smokers attending the practice each day. One-year smoking cessation was validated by cotinine saliva analysis. The validated three-month sustained abstinence rates at one year were 8.1 percent and 9.8 percent in the gum and no-gum groups, respectively. The 95 percent confidence interval about this difference was -9.3 percent to 6.4 percent. There is no evidence from this study that the offer of 2 mg of nicotine-bearing gum enhances smoking cessation rates when added to a comprehensive intervention offered to all smokers in primary care. Until larger trials are completed, however, the possibility that this dose of nicotine gum may produce small beneficial effects cannot be excluded.

Chewing Gum↗
PubMed1988

A randomized trial of a family physician intervention for smoking cessation.

We assessed the impact of three conditions on one-year smoking cessation rates. Physicians in 70 community general practices were randomly allocated by practice to one of three groups: In the usual care group, smoking patients were to receive the care they normally would receive. In the gum only group, physicians were asked to speak to patients about smoking cessation and offer nicotine gum. In the gum plus group, physicians were trained in the experimental intervention. This intervention involved advice to stop smoking, the setting of a quit date, the offer of nicotine gum, and four follow-up visits. Smoking cessation was measured by self-report after one year and validated using saliva cotinine measures. Using a criterion of at least three months of abstinence, 8.8% of the patients of the trained physicians had stopped smoking at the one-year follow-up compared with 4.4% and 6.1% of the patients in the usual care and gum only groups, respectively.

Adolescent↗
PubMed1988

A controlled trial of digoxin in congestive heart failure.

Because of conflicting results from studies examining the usefulness of digoxin in congestive heart failure (CHF) patients in sinus rhythm, a cross-over trial was conducted in which 20 patients received 7 weeks of digoxin titrated to a level of 1.54 to 2.56 nmol/liter and 7 weeks of matched placebo. The order of treatments was determined by random allocation and patients, clinicians and research staff were blind to allocation. In patients with deteriorating condition, the treatment period was terminated and outcome measures were obtained. If deterioration occurred during the first period, the patient was crossed over without the code being broken. Seven patients required premature termination of study periods because of increasing symptoms of CHF. All 7 were taking placebo at the time (p = 0.016). Small differences in dyspnea (p = 0.044), walking test score (p = 0.055), clinical assessment of CHF (p = 0.036) and ejection fraction (p = 0.004) favored the digoxin treatment group. Patients with more severe CHF were more likely to benefit from digoxin administration. It was concluded that oral digoxin, in doses titrated to produce a serum level of 1.54 to 2.56 nmol/liter, improved quality of life and functional exercise capacity in some patients with CHF in sinus rhythm.

Aged↗
PubMed1988

Cloning of the gene encoding a 50 kilodalton potential surface antigen of Schistosoma mansoni.

A cDNA library was constructed from the mRNA of adult worms of Schistosoma mansoni, in the expression vector lambda gt11. This library was screened with a pool of sera raised against either soluble egg antigens or purified schistosomulum tegumental membranes. An antiserum raised against the fusion protein of one clone immunoprecipitated a 45 kDa polypeptide from the in vitro translation products of adult worm mRNA and recognised a 50 kDa antigen in homogenates of adult worms. This serum gave positive fluorescence of the surface of schistosomula in indirect immunofluorescence assays and was able to mediate killing of schistosomula by human eosinophils in vitro, suggesting that this clone contained part of a gene encoding a surface antigen.

Animals↗
PubMed1988

Gastrointestinal hemorrhage from fistula between traumatic pseudoaneurysm of the right hepatic artery and the duodenum.

The evaluation of gastrointestinal hemorrhage after abdominal trauma may be both urgent and difficult. After gunshot trauma, a fistula between the duodenum and a post-traumatic, hepatic artery pseudoaneurysm presented as a gastrointestinal hemorrhage. Tc-99m labeled RBC imaging demonstrated the pseudoaneurysm but did not show it as the source of the gastrointestinal hemorrhage--a large clot had formed, occluding the fistula. Angiography further delineated the lesion as arising from the right hepatic artery and transcatheter embolization was performed.

Aneurysm↗
PubMed1988

Inbred mice infected with Plasmodium yoelii differ in their antimalarial immunoglobulin isotype response.

Antibodies are known to be important in mediating malarial immunity, but the influence of the various immunoglobulin isotypes on parasite elimination is unclear. The purpose of this study was to provide basic information on the induction of isotype expression in genetically different mice during primary malaria. Parasitaemias and the serum antimalarial IgM, IgG1, IgG2, IgG3 and IgA antibody titres measured in a radioimmunoassay were followed in outbred and 11 inbred strains of mice infected with 17XNL Plasmodium yoelii. Severity of infection, as judged by length of infection, peak parasitaemias and death, was found to differ between the strains. All strains developed rapid IgM responses, but only 3/11 inbred strains produced significant antimalarial IgG1 levels during primary infection. All strains produced an IgG2 response, which developed slightly more quickly in strains with the least severe courses of malaria. A large variation in the IgG3 response was noted between strains. In general, IgG3 antibodies were the first IgG-isotype to appear in serum. They were detected as early as day 8 in strains that developed mild infections but were not present until around day 20 in strains with the most severe cases of malaria. Only one strain produced detectable antimalarial IgA antibodies. These results show that different patterns of isotype expression are induced in inbred strains of mice during primary P. yoelii infection.

Animals↗
PubMed1988

Expression of the histidine-rich protein PfHRP1 by knob-positive Plasmodium falciparum is not sufficient for cytoadherence of infected erythrocytes.

Six culture-adapted knob-positive Plasmodium falciparum parasites, four of which were nonbinding in an in vitro cytoadherence assay, were tested for the presence of the knob-associated histidine-rich protein PfHRP1. Two knob-positive, strongly cytoadherence-positive P. falciparum strains from Aotus monkeys were also examined. All parasites expressed PfHRP1, suggesting that it plays a structural or functional role related to knobs but is not by itself sufficient for cytoadherence of P. falciparum-infected erythrocytes.

Animals↗
PubMed1988

Dialyzer re-use--a multiple crossover study with random allocation to order of treatment.

A multiple crossover research study was used to evaluate the effect of dialyzer re-use on fever, blood leaks, serum urea and creatinine values and symptoms. Each of 6 crossover periods consisted of 4 weeks on either single-use or re-use, 1 week washout, 4 weeks on the alternative treatment and 1 week washout. The re-use consisted of 6 uses of each dialyzer and the washout weeks consisted of 3 single-use sessions. Analysis of paired observations within rather than between patients showed no effects of time (i.e. among crossover periods 1 through 6) or number of re-uses (i.e. among uses 1 through 6). There was no significant difference for temperature change during dialysis, blood leak rate, or the serum urea and creatinine values before the first dialysis of each washout period. There were no differences for symptoms of pruritus, cramps, nausea, headache, chest pain, backache or fatigue. There were no clinical advantages or disadvantages associated with dialyzer re-use.

Cellulose↗
PubMed1988

Immunoprecipitation of Fasciola hepatica mRNA in vitro translation products using infection and hyperimmune sera.

Total RNA containing messenger RNA has been isolated from adult Fasciola hepatica and translated in vitro using the rabbit reticulocyte lysate system. L-[35S]-methionine labeled translation products have been immunoprecipitated with sera collected from rabbits infected with F. hepatica, rabbits immunized with adult worm homogenate, and a rabbit and 5 calves immunized with a Fasciola/Schistosoma cross-reactive, cross-protective antigen, denoted FhSmIII(M). Precipitated antigens were analyzed by SDS-polyacrylamide gel electrophoresis. The major antigens recognized by hyperimmune sera had apparent molecular weights of 12,500, 13,500, 14,000, 26,500, and 27,000. The rabbit anti-FhSmIII(M) serum precipitated a 13,500 Mr antigen. Sera collected from calves immunized with FhSmIII(M) also precipitated a 13,500 Mr antigen together with a 26,500 Mr molecule. Antibody with specificity for F. hepatica mRNA translation products could be detected in rabbit serum 2 weeks after infection.

Animals↗
PubMed1988

Isolation and in vitro translation of Onchocerca volvulus mRNA.

Adult Onchocerca volvulus recovered for excised nodules by dissection or treatment with collagenase have been used as a source of RNA for in vitro translation experiments. RNA was purified using either the hot phenol/SDS procedure or the guanidine isothiocyanate protocol. Immunoprecipitation experiments performed on in vitro products demonstrate a marked heterogeneity in responses by individed human infection sera. Further immunoprecipitation experiments demonstrate cross reactivity between O. volvulus and other filarial nematodes.

Animals↗