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Biomedical subjects

M A Miles

Publications and source records attributed to M A Miles.

At least 73 records · Page 4Linked to original sources
PubMed1990

Efficient diagnosis of giardiasis among nursery and primary school children in Santiago, Chile by capture ELISA for the detection of fecal Giardia antigens.

Fecal samples were obtained from 722 of 820 children attending 7 nursery schools and 1 primary school in the city of Santiago, Chile. Microscopy of formol-ether concentrates showed that 33% of the children were infected with Giardia lamblia. Prevalences among primary school students (5-10 years of age) of G. lamblia (38%), Endolimax nana (43%), and Entamoeba coli (25%) were overall higher than among nursery school students (3 months-5 years of age; prevalences 29%, 21%, and 16%, respectively). There was no apparent association between socio-economic intake and levels of G. lamblia infection: the private nursery school had the highest recorded level of infection (40%). One hundred sixty-two triplicate stool specimens were used to compare microscopy with an enzyme-linked immunosorbent assay (ELISA) for the detection of Giardia fecal antigens. The ELISA was highly sensitive and specific either visually (95% and 97%, respectively) or by optical density determination (99% and 96%, respectively). Incorporation of non-immune rabbit immunoglobulin-coated control wells did not enhance sensitivity and specificity. The antigen detection ELISA is an extremely effective tool for the epidemiological investigation of giardiasis.

Animals↗
PubMed1990

Trypanosoma cruzi infection in the Mexican state of Guerrero: a seroepidemiological (ELISA) survey of 20 communities.

The enzyme linked immunosorbent assay (ELISA) was used to analyse 4372 blood samples from residents of 978 households in 20 representative communities in the Mexican state of Guerrero. Seventy-five individuals had very high titres of antibodies against Trypanosoma cruzi. Samples with intermediate optical density values, despite overlapping values with several control positives on a single-well test, did not sustain their positivity at high dilutions. 'Intermediate positives' had a different distribution among the 20 communities to samples sustaining reactivity at high dilutions, indicating possible cross-reactivity with another infectious agent. The finding of seropositive children under the age of 10 years in the Costa Chica, Acapulco and the Tierra Caliente regions, with family clustering of putative cases, indicates that recent transmission must be considered. Very few people interviewed in the 20 communities knew the triatomine bug could transmit a disease.

Age Factors↗
PubMed1989

Immunoselection techniques for cloning DNA-encoding parasite-specific antigens.

New techniques sometimes generate a 'band- waggon' effect, with research workers keen to jump on and apply the technique in their own favourite field without always pausing to consider why. Michael Miles and Louise Clarke describe a new technique which they are applying to a well-defined and valuable end - improvement in the differential diagnosis of parasitic infections.

Journal Article↗
PubMed1989

Multiple peptide synthesis (Pepscan method) for the systematic analysis of B- and T-cell epitopes: Application to parasite proteins.

In 1984 Mario Geysen and his colleagues described a technique for the simultaneous synthesis of hundreds of peptides on polyethylene rods. The peptides, still on the rods, could be used directly in enzyme-linked immunosorbent assays (ELISAs) and in this way linear parts of B-cell epitopes could be mapped. For the analysis of T-cell epitopes, peptides can be cleaved from the rods and incorporated into proliferation assays. This method, called the 'Pepscan' procedure, has been used for the detailed characterization of epitopes of viruses, Chlamydia and Mycobacteria: it is a powerful new approach to the epitope mapping of parasite proteins.

Journal Article↗
PubMed1988

Trypanosoma cruzi: studies on the interactions of lectins with glycoconjugates of different zymodemes.

Detergent extracts were made of eight strains of Trypanosoma cruzi which were representative of the principal zymodemes. The extracts were subjected to sodium dodecyl sulfate-polyacrylamide gel electrophoresis and the glycoproteins were reacted with 21 different 125I-labeled lectins and autoradiographed. The staining patterns with particular lectins varied considerably between strains. Concanavalin A stained up to 17 distinct bands in some strains. Other lectins such as peanut lectin only stained two bands in zymodeme 1 strains and none in the other zymodemes. The reaction of N-acetylgalactosamine-specific lectins with some bands indicated the presence of this sugar and this was confirmed by analysis of the extracts. The lectin staining patterns provided an insight into the glycoprotein composition of the bands and should indicate whether combinations of lectins can be used in affinity chromatography systems to purify the glycoproteins.

Animals↗
PubMed1988

Specific serodiagnosis of visceral leishmaniasis using a Leishmania donovani antigen identified by expression cloning.

A lambda gt11 expression library was constructed using mRNA from the promastigote form of Leishmania donovani (African isolate MHOM/ET/67/HU3). The library was screened with serum obtained from a patient who contracted visceral leishmaniasis in the Sudan. Several cDNA clones which expressed beta-galactosidase/L. donovani antigen fusion proteins were isolated. One of these clones corresponded to a 60 kDa membrane-associated antigen. By a Western blot assay antibodies against the fusion protein were detected universally in the sera of visceral leishmaniasis patients. They were not detected in sera from patients with cutaneous leishmaniasis or other parasitic protozoan infections. The gene coding for this antigen was specific to the genus Leishmania as judged by DNA hybridisation, and its chromosomal location was conserved. A 20 kb mRNA was detected on Northern blots of promastigote RNA.

Animals↗
PubMed1988

Viruses of parasitic protozoa.

Associations are increasingly recognized between parasitic protozoa and smaller organisms such as bacteria (see Parasitology Today 1, 143), and viruses. Their revelation, originally by ultrastructural studies, may now be indicated by observations of 'rogue bands' on gel electrophoresis of parasite nucleic acids. The origins and roles of parasite 'parasites' are still uncertain, but, as Michael Miles suggests here, they may prove of particular importance as agents to introduce genes for important immunogens into non-pathogenic protozoa for vaccine delivery.

Journal Article↗
PubMed1988

Radiolabeled total parasite DNA probe specifically detects Trypanosoma cruzi in mammalian blood.

A DNA-DNA hybridization procedure is described in which radiolabeled total parasite DNA is used to detect Trypanosoma cruzi spotted directly onto nylon membrane. Under conditions that favor hybridization of repetitive DNA sequences, the radiolabeled total DNA was able to detect as few as five parasites spotted onto nylon membrane. Trypanosomes were detectable in blood from mice with T. cruzi parasitemias spotted directly onto membranes. All 10 strains of T. cruzi examined, which came from different areas of the United States and South America, were readily detected with a total DNA probe from any 1 strain of the parasite. No signals were detected with up to 20,000 Trypanosoma rangeli, T. brucei, Crithidia fasciculata, or Leishmania parasites or with normal mouse blood or mammalian DNA. The hybridization method is sensitive, specific, rapid, and inexpensive and is potentially applicable to the detection of other parasites.

Animals↗
PubMed1987

Leishmania donovani metacyclic promastigotes: transformation in vitro, lectin agglutination, complement resistance, and infectivity.

Freshly transformed Leishmania donovani amastigotes from hamster spleen were used to establish axenic cultures at high density in a modified Grace's medium, which was only partly replenished when cultures were fed. Small, free-swimming, highly active stationary phase promastigotes with a short cell body and long flagellum were induced in this medium. The freshly transformed stationary phase promastigotes so induced were less able to bind peanut agglutinin, had more than 40-fold increased resistance to killing by normal human serum, and 15-fold increased infectivity both in vivo and in vitro when compared to freshly transformed logarithmic phase or long term culture promastigotes. These short form promastigotes may correspond to the metacyclic promastigote forms in the sand fly vector.

Agglutination↗
PubMed1987

Schizodeme analyses of Trypanosoma cruzi zymodemes from Chile.

Kinetoplast DNA was isolated from Chilean Trypanosoma cruzi populations and digested with the restriction endonucleases EcoRI, HinfI, HpaII, MspI, and HaeIII. Three major schizodeme groups were discriminated. There was a correlation between the Chilean schizodeme groups (S1, S2, or S3) and the zymodemes known to occur in Chile (Z1, Brazilian Z2 and Bolivian Z2, respectively), although heterogeneity was seen within the schizodeme groups S2 and S3. Standard Brazilian and Bolivian T. cruzi clones (X10 clone 1, Esmeraldo clone 3, SC43 clone 1, and CAN III clone 1) and laboratory strains (Tulahuen and Y) were included in the schizodeme comparisons. SC43 clone 1 had obvious affinities with S3 and X10 clone 1 shared some features with S1 but the other reference stocks could not be definitely assigned to S1, S2, or S3. Fragment patterns and densitometric traces following digestion with HpaII or MspI suggested that kDNA sequences were not methylated.

Animals↗
PubMed1987

Chromosome size polymorphisms of Leishmania donovani.

A minimum of 22 chromosomes were found in all Leishmania donovani stocks examined by orthogonal field alternation gel electrophoresis (OFAGE). Chromosome sizes ranged from approximately 270 to 4000 kb. Certain chromosomes were polymorphic in size between stocks and chromosomes present in some stocks had no apparent equivalent in others. Specific polymorphisms were useful in distinguishing the subspecies L. d. donovani, L. d. infantum and L. d. chagasi and African L. donovani stocks but there were karotypic differences within these taxa. Radiolabelled DNA derived from whole chromosomes was hybridised to OFAGE Southern blots. Chromosome 1 of L. d. donovani was homologous to two larger chromosomes in all stocks. Chromosome 2 of certain L. d. chagasi and L. d. infantum stocks was homologous to both chromosomes 2 and 3 of L. d. donovani: this suggested that translocation between chromosomes may have contributed to the size polymorphisms. The smallest chromosome seen (270 kb) was unique to the African stock HU3. It was not homologous to small chromosomes in L. d. donovani, L. d. infantum or L. d. chagasi. The small chromosome did hybridise to two small chromosomes in another African stock, Khartoum, and to a large chromosome present in all stocks. The beta-tubulin gene was mapped to chromosomes 21/22, 13 and 7 with strongest hybridisation to 21/22. alpha-Tubulin was mapped to chromosomes 9. The alpha- and beta-tubulin arrangement was highly conserved.

Animals↗
PubMed1987

Temperature modulation of growth rates and glucosephosphate isomerase isozyme activity in Trypanosoma cruzi.

In an attempt to understand the conditions which might influence the geographical distribution of Trypanosoma cruzi isozyme profiles (zymodemes), the thermal response of different glucosephosphate isomerase (GPI) phenotypes was studied. T. cruzi clones with single- and triple-banded GPI phenotype showed a similar response to temperature with respect to both growth rates and GPI kinetic parameters. However, the relative activity of each GPI isozyme was dependent on parasite incubation temperature. In view of the similar kinetic properties of the isozymes, enzyme regulation is not a consequence of an adaptative response to thermal conditions and the suggestion of a phenotype distribution determined selectively by temperature is not supported by the present study.

Animals↗
PubMed1987

Overfeeding during early pregnancy reduces peripheral progesterone concentration and pregnancy rate in sheep.

The 330 Merino ewes used in the study were placed with rams at a synchronized oestrus and, on Days 2-14 after mating, the ewes were placed in a feed lot and fed daily a low, medium or high ration (25%, 100% or 200% of maintenance respectively). Progesterone supplement was given to some ewes on Days 8-14 after mating by using a device containing 340 mg progesterone. Blood samples were taken from all ewes on Day 12 for measurement of plasma progesterone concentrations. On Day 14 after mating all ewes were returned to pasture. Pregnancy rate was determined by returns to oestrus and was later confirmed using ultrasound. There was a decline in the peripheral progesterone concentrations with increasing ration. The pregnancy rate in ewes fed a high ration was significantly reduced when compared with those of ewes fed a medium or low ration (48% vs 68 and 67% respectively; P less than 0.05). In ewes fed the high ration exogenous progesterone increased the pregnancy rate from 48 to 76% (P less than 0.01). Progesterone treatment did not influence pregnancy rates in ewes fed medium or low rations. The number of fetuses per ewe pregnant was not influenced by level of nutrition or progesterone treatment.

Animal Nutritional Physiological Phenomena↗
PubMed1987

Epidemiology of Chagas' disease in northern Chile: isozyme profiles of Trypanosoma cruzi from domestic and sylvatic transmission cycles and their association with cardiopathy.

Trypanosoma cruzi was isolated from 98 patients, 59 Triatoma infestans, 51 Triatoma spinolai, and 1 Octodon degus from northern Chile. With few exceptions, stocks originating from domestic hosts were classified, based on their isozyme profile, as principal zymodeme (Z)2, while sylvatic stocks from T. spinolai and the rodent O. degus showed Z1 profiles. These results indicate the existence of separate domestic and sylvatic transmission cycles. Clinical data and T. cruzi isozyme profiles from 107 chronic Chagas' disease patients showed no association between infecting T. cruzi zymodeme and the prevalence of chagasic cardiopathy. However, the age distributions of two groups of patients carrying different zymodemes were significantly different.

Adolescent↗