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Biomedical subjects

C A Hall

Publications and source records attributed to C A Hall.

At least 109 records · Page 6Linked to original sources
PubMed1979

The anthelmintic efficacy of albendazole against Fasciola hepatica and benzimidazole resistant strains of Haemonchus contortus and Trichostrongylus colubriformis in sheep.

The anthelmintic efficacy of albendazole (methyl [5-(propylthio) - 1H - benzimidazole -2 -yl] carbamate) against immature and adult Fasciola hepatica and against standardised strains of benzimidazole resistant Haemonchus contortus and Trichostrongylus colubriformis was evaluated in experimentally infected sheep. A single intrarumenal treatment of dose rates of 3.8 and 7.6 mg/kg was ineffective against immature (six weeks old) F hepatica. Dose rates of 5.7 and 7.6 mg/kg reduced the number of mature (12 weeks old) F hepatica by 70 and 91 per cent respectively. Dose rates of 5.7 and 7.6 mg/kg removed 92 and 99 per cent of four-week-old, benzimidazole resistant H contortus and 89 and 99 per cent of four-week-old, benzimidazole resistant T colubriformis.

Animals↗
PubMed1979

The forms and transport of plasma cobalamins in normal man and in myeloproliferative states.

Seven patients with MP and four controls were injected with 0.04 to 0.05 microgram of [57Co] cyanocobalamin i.m. or i.v. in order to study the shift of binding with time and the conversion of one Cbl to another. The initial pattern of binding reflected the proportion of the apo forms of TC II and R binders. In MP there was more initial binding of the injected Cbl to R-type binders and less to TC II. During the first 48 hr after intake, the injected Cbl remained mostly as cyanocobalamin. Some adenosylcobalamin appeared transiently in both control and MP subjects. Radioactive methylcobalamin did not appear in the circulation until after 48 hr, and the conversion of cyanocobalamin to methylcobalamin within the circulation was greater in MP subjects. Serum from some subjects converted small amounts of cyanocobalamin to all other forms in vitro by a heat-stable, extracellular property which was abolished by dialysis of the serum. This property of serum could have accounted for the early conversion to adenosylcobalamin but not, at least as an in vitro phenomenon, to the late appearance of methylcobalamin. Although the expected increases and abnormal patterns of R binders were observed in MP, these abnormalities could not be correlated with the increased conversion to plasma methylcobalamin. During the first 6 hr after injection the R binder-Cbl designated as alpha 2-R-Cbl disappeared from the circulation at a rate faster than that of alpha 1-R-Cbl. Subsequently the alpha 2 and alpha 1 components of R binder-Clb cleared at the same rate, and this rate was the same for both control and MP subjects.

Carrier Proteins↗
PubMed1978

Preparation of radioactive labelled (57Co) sulfitocobalamin.

Farquharson and Adams (Br. J. Nutr. 36, 127-135 (1976)) have identified sulfitocobalamin (SO3-Cb1) as one of the naturally occurring cobalamins (Cb1s) in foods. We have devised a method of making radioactive labelled SO3-Cb1 for in vivo and in vitro studies of this form of Cb1. 57Co labelled cyanocobalamin (57Co CN-Cb1) was acid photolyzed to 57Co hydroxocobalamin (57Co OH-Cb1) followed by ligand substitution with SO3-2 ion from aqueous sodium (meta) bisulfite in the dark. The resulting 57Co SO3-Cb1 was purified by organic extraction and cation exchange chromatography. The final preparation was greater than 99% 57Co SO3-Cb1 with an overall yield of greater than 70%, stable for up to four weeks at 20 degrees C in the dark, and capable of binding to the human Cb1 binding proteins Transcobalamin II (TC II), Intrinsic factor (IF) and Salivary R. This method allows a simple 1 day preparation of high specific activity labelled 57CO SO3-Cb1 for biological studies.

Cobalt Radioisotopes↗
PubMed1978

Peptones and mycological reproducibility.

The pH reactions, ultraviolet spectra and phosphorus content of solutions of a variety of commercially available peptones all indicated, predictably, considerable differences in the chemical composition of the peptones. The effects of these differences on the outcome of experiments with Candida albicans grown in different peptone media was investigated. The fungus produced germ tubes equally effectively on all such media provided that the inoculum was kept to 10(6) blastospores/ml or less. However, expression of inducible enzyme activities in C. albicans varied extensively from peptone to peptone; there was, for example, an inverse relationship between the inorganic phosphorus content of peptones and the amount of acid phosphomonoesterase detectable in intact blastospores. The results indicated that use of different peptones in "Sabouraud's" media by different laboratories may account for some, but not all, published instances of irreproducibility of experiments with C. albicans.

Acid Phosphatase↗
PubMed1978

The anthelmintic efficacy of non-benzimidazole anthelmintics against benzimidazole resistant strains of Haemonchus contortus and Trichostrongylus colubriformis in sheep.

The anthelmintic efficacy of 6 non-benzimidazole compounds and thiabendazole against standardised, benzimidazole resistant strains of H. contortus and T. colubriformis in sheep was determined using a controlled test. All compounds were administered intraruminally at their recommended therapeutic dose rates and 4 of the compounds were also assessed at half their recommended therapeutic dose rates. Levimisole at a dose of 6.4 mg/kg body weight, morantel at 4.4 mg/kg and 8.8 mg/kg, naphthalophos at 6.25 mg/kg and 12.5 mg/kg, rafoxanide at 7.5 mg/kg and phenothiazine at 530 mg/kg were 98% or more effective in removing adult infections of benzimidazole resistant H. contortus. Rafoxanide at 3.75 mg/kg, phenothiazine at 265 mg/kg and carbon tetrachloride at 0.05ml/kg were less effective, removing 80%, 73% and 72% respectively of the benzimidazole resistant H. contortus worm burdens. Against the benzimidazole resistant T. colubriformis levamisole at 6.4 mg/kg, and morantel at 4.4 mg/kg and 8.8 mg/kg removed 99%, 68% and 86% respectively of the adult infections. All other anthelmintics had little or no efficacy at the dose rates tested. Thiabendazole at 44 mg/kg had no significant effect against these strains of H. contortus and T. colubriformis. Several non-benzimidazole anthelmintics have shown high efficacy in this experiment and should be suitable for treating infections with benzimidazole resistant H. contortus. Of the anthelmintics tested, only levamisole and morantel show high efficacy against benzimidazole resistant T. colubriformis.

Animals↗
PubMed1978

Levels of benzimidazole resistance in Haemonchus contortus and Trichostrongylus colubriformis recorded from an egg hatch test procedure.

A method of using commercially available benzimidazole anthelmintics in an egg hatch test, to record levels of resistance is described. The test shows that a side-resistance is present to all the benzimidazole anthelmintics tested against both Haemonchus contortus and Trichostrongylus colubriformis after selection with thiabendazole. Additional selection on the field resistant strain of H contortus with thiabendazole showed increased levels of resistance to all the compounds tested while similar selection of T colubriformis failed to change the level of resistance after 20 generations. The level of resistance recorded by the egg hatch test in vitro is greater than that recorded for adults in vivo for the CF strain of H contortus and T colubriformis. Problems associated with reading the test are mentioned as are the different levels for the threshold of activity.

Animals↗
PubMed1978

The dose response of several benzimidazole anthelmintics against resistant strains of Haemonchus contortus and Trichostrongylus colubriformis selected with thiabendazole.

Dose response lines for eight benzimidazole anthelmintics and thiophanate were determined, using standardised strains of thiabendazole selected and resistant Haemonchus contortus and Trichostrongylus colubriformis. Against H contortus, thiophanate, thiabendazole, parbendazole and oxibendazole were inactive. Mebendazole was inactive at dose rates of 6.26 and 12.5 mg/kg, although significant activity occurred at 25 mg/kg. Fenbendazole, cambendazole, oxfendazole and albendazole demonstrated significant activity at dose rates equal to or greater than the recommended therapeutic level. Thiophanate was inactive against resistant T colubriformis. The remaining compounds only showed significant activity when used at dose rates in excess of the recommended therapeutic level. These results show that a side resistance exists among the benzimidazole anthelmintics and suggests that changes in dose response lines could be expected to occur if resistant strains are selected with benzimidazoles other than thiabendazole.

Animals↗
PubMed1978

Physiological characteristics of free-living and parasitic stages of strains of Haemonchus contortus, susceptible or resistant to benzimidazole anthelmintics.

The effect of changes in genetic constitution (associated with developing benzimidazole resistance) on the physiological characteristics of Haemonchus contortus was investigated. Benzimidazole resistant H contortus were significantly more infective for sheep (20 per cent) than benzimidazole susceptible strains. Pathological changes were more severe in sheep infected with resistant H contortus as measured by packed cell volume, plasma protein concentration and haemoglobin levels. Faecal egg output was significantly higher for resistant strains as was the development and survival of eggs and free-living stages on pasture. Infective third stage larvae of benzimidazole resistant H contortus had a significantly faster exsheathment rate in rumenal fluid than did susceptible strains. These adaptive changes in response to continuing anthelmintic selection of resistant worm populations are discussed and the implications of these findings for worm control programmes indicated.

Animals↗
PubMed1977

A radioimmunoassay for the R-type binders of cobalamin.

A radioimmunoassay of R-type binders of cobalmin was devised and tested. The assay incorporated an antibody against purified human salivary R binder as the binding reagent. The labeled ligand was cyano[57Co]cobalamin bound to the R binder of pooled human saliva. The standard source of unlabeled ligand was also from human saliva of known R binder content. The assay was responsive to R binders of several sources, to either pure R or that of crude sources and equally to R binder saturated or unsaturated with cobalamin. It was not responsive to transcobalamin II. The assay was reproducible and reliable.

Antibody Specificity↗