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Biomedical subjects

B F Stone

Publications and source records attributed to B F Stone.

32 records · Page 2Linked to original sources
PubMed1977

Aggregation pheromones in 2 Australian hard ticks, Ixodes holocyclus and Aponomma concolor.

The presence of an aggregation pheromone has been demonstrated for the first time in indigenous Australian ticks. Filter paper discs exposed to either Australian paralysis ticks Ixodes holocyclus or echidna ticks Aponomma concolor showed inter-sex or intra-sex attraction for ticks of their own species. Nymphal exuviae of Ap, concolor were highly attractive to adult ticks. Discs were significantly attractive to I. holocyclus at distances up to 80 cm.

Animals↗
PubMed1976

Linkage and dominance characteristics of genes for resistance to organophosphorus acaricides and allelic inheritance of decreased brain cholinesterase activity in three strains of the cattle tick, Boophilus microplus.

Resistance to the organophosphorus acaricides diazinon, dimethoate and formothion in the Biarra (B), Mackay (M) and Ridgelands (R) strains respectively of the cattle tick B. microplus has been shown previously to be controlled in each strain by a single incompletely dominant autosomal genetic factor. A very similar mode of inheritance of fenthion resistance in strain B has now been demonstrated with no departure in degree of dominance of resistance from the mean value of +0-57 common to these strains exposed to these chemicals. No F1 larval progeny from the following crossings were appreciably more resistant than their parents to these chemicals: R x B--bromophos ethyl and fenthion; B x M--carbaryl, chlorfenvinphos, chlorpyrifos, diazinon, dimethoate, ethion, fenthion and formothion; M x R--chlorfenvinphos, diazinon, dimethoate, ethion, formothion. The field importance of this absence of overdominance is discussed. There were no susceptible double recessive F2 larval progeny of B x M crossings of F2 or F3 larval progeny of R x M crossings when tested against dimethoate to which the three parental types were similarly resistant; 1/16 of the larval progeny would be expected to be completely susceptible if the resistance genes were unlinked. F1 adult progeny of B x M and R x M crossings exhibited the incompletely recessive mutant-type decreased brain acetylcholinesterase (AChE) activity common to strains B, M and R, thus satisfying the test for allelism. No ticks with normal levels of brain AChE were detected in F2 adult progeny of B x M or R x M crossings. This evidence was strongly suggestive of a series of closely linked genes or alleles controlling dimethoate resistance and a series of alleles controlling decreased brain AChE activity in strains B, M and R.

Acetylcholinesterase↗
PubMed1976

Biochemical genetics of resistance to organophosphorus acaricides in three strains of the cattle tick, Boophilus microplus.

Three aspects of the biochemical genetics of resistance to organophosphorus compounds in the Biarra (B), Mackay (M) and Ridgelands (R) strains of the cattle tick B. microplus were studied. These were: decreased acetylcholinesterase (AChE) activity in adult brains of strains B and M; decreased AChE sensitivity to inhibitors in adult brains and in larvae of strains B, M and R; and increased detoxication in larvae and adult females of strain M. Comparisons were made with a susceptible reference strain (S). Microspectrophotometric estimations of AChE activity in histochemical preparations of whole brains showed that hybrids had levels of activity approximately intermediate between those of the parental strains. Homogenates of brains from hybrids assayed biochemically gave similar but more precise results which indicated that decreased brain AChE activity was neither recessive nor dominant (degree of dominance, D = +0-02) in strain B and incompletely recessive (D = -0-26) in strain M. The proportions of brains showing decreased AChE activity in testcross and F2 progenies indicated that decreased AChE activity in strains B and M is controlled by single autosomal genes. Inhibition of AChE at diagnostic concentrations of coroxon in brains of B, B x S hybrid and S types suggested that decreased sensitivity of AChE in strain B is incompletely dominant (D = +0-10). Kinetic studies on coroxon inhibition of AChE in brain homogenates of B, B x S hybrid and S types revealed the presence of each parental AChE component in hybrids in equal amounts and the absence of a hybrid enzyme. Dimethoxon inhibition of AChE in brains, their homogenates and larval homogenates of B, M and R types showed that decreased AChE sensitivity was a major mechanism of resistance to dimethoate strongly expressed in B x S and M x S hybrids. The proportion of brains showing decreased AChE sensitivity to coroxon in testocross and F2 progenies indicated that decreased AChE sensitivity in strain B is controlled by a single autosomal gene. The degree of dominance of increased degradative metabolism of coumaphos in strain M was variable; the hydrolytic rate in all M x S hybrids was similar to that of M but the overall detoxication rate in hybrids was lower. Genetic control of detoxication is discussed.

Acetylcholinesterase↗
PubMed1969

Mechanisms of resistance to fenthion in Culex pipiens fatigans Wied.

One of the insecticides of choice to control the mosquito Culex pipiens fatigans, a vector of Bancroftian filariasis, is fenthion. The mechanism of resistance to this insecticide which could develop in C. p. fatigans was investigated in a strain from Rangoon, Burma, made 8 times more fenthion-resistant than normal by laboratory selection, by exposing the larvae to (32)P-fenthion and examining the metabolites.Larvae of the resistant strain were found to absorb about half as much fenthion as those of the corresponding normal strain, and they degraded proportionately about twice the amount absorbed to water-soluble metabolites. Thus, the larval content of chloroform-soluble toxicants remaining was only one-third to one-seventh as much in the resistant as in the normal strain. The production of the non-toxic hydrolytic (water-soluble) metabolites was 70% greater in the resistant strain in absolute terms, despite the lower amount absorbed into the larvae. The greatest increase (4-fold) was in the oxonase activity, although the thionase activity was more important in both strains.Esterase zymograms from agar-gel electrophoresis revealed a principal band which was much more intense in the resistant than in the susceptible strain, as judged by its hydrolysis of alpha- and beta-naphthyl acetates and phosphates. This band was comparatively insensitive to the toxicant fenoxon, and could hydrolyse it.

Animals↗