Gary M. Booth

Phenylthioacetate: A Useful Substrate for the Histochemical and Colorimetric Detection of Cholinesterase

Cholinesterase from frozen sections of honey bee (Apis mellifera, L.) brain hydrolyzes phenylthioacetate and acetylthiocholine to give virtually identical patterns of enzyme distribution with and without the use of paraoxon. In addition, phenylthioacetate is an economical substrate for in vitro and in vivo studies of cholinesterase. Phenylthioacetate offers the advantages of being easily synthesized and lipoid soluble, and appears to penetrate membranes easily.

General morphology of the brain of the blind cave beetle, Neaphaenops tellkampfii Erichson (Coleoptera : Carabidae)

Abstract Neaphaenops tellkampfii (Coleoptera : Carabidae) was collected from Cartmill Cave located in Hart County, Kentucky, U.S.A. This is a cave insect with complete absence of external evidence of eyes or ocelli. The brain of N. tellkampfii has been studied at the light microscope level using Rowells (1963) silver staining method. Particular attention has been paid to the protocerebrum. One of the notable features of the brain is the dominance of the corpora pedunculata. The corpora pedunculata consists of a calyx, with 3 groups of fibers originating from the Kenyon cells. The stalk is arranged into 2 distinct layers with alpha and beta lobes. The central complex is located anterio-medially beneath the pons cerebralis. It consists of central and ellipsoid bodies and a single ventral tubercle. The ellipsoid body is connected to the beta lobes by a unique chiasmatic fiber tract. The pons cerebralis appears to be formed by 3 distinct groups of globuli cells sending fibers into the pons. The accessory lobes are situated posterio-laterally. The antennal lobes are located posterio-ventrally. Two tubercles were observed lateral to the protocerebrum which may be vestigial optic tubercles. There is no evidence of typical optic lobes or associated fiber tracts. Fiber connections were observed between the calyx and pons cerebralis, the calyx and central body, and also between the calyx and antennal lobe. Two fiber tracts not previously described were observed extending obliquely from the accessory lobe to the beta lobe and protocerebrum.

Histochemical specificity of cholinesterases to phenylthioacetate in differentiated neural tissues of insects and teleosts.

Housefly brain cholinesterase was histochemically demonstrated to hydrolyse phenylthioacetate at a very high rate, similar in distribution to that previously reported for acetylthiocholine. However, teleost neural retina cholinesterase would not hydrolyse the aromatic substrate, but the enzyme did cleave acetylthiocholine. Paraoxon and eserine were utilized to show selective patterns of inhibition in the two tissues. This high degree of substrate selectivity is discussed in conjunction with the possible development of selective insecticides.

Electrophoretic and histochemical analysis of esterase synthesis in the ovariole of the milkweed bugOncopeltus fasciatus (Dall.)

SummaryThe synthesis of esterases was analysed in the ovariole of the milkweed bug using electrophoretic and histochemical methods. We found a total of 12 esterases from whole ovaries. Using the inhibitors p-hydroxymercuribenzoate, diisopropyl phosphorofluoridate and eserine, 3 of the bands were classed as acetylesterases, 7 carboxylesterases, and 2 arylesterases. No change in esterase patterns occurred during oogenesis.The esterase activity in the follicular epithelium was primarily arylesterase and carboxylesterase. A carboxylesterase was also identified from the central region of the follicle cell. The yolk cells contained mainly carboxylesterase. There was an apparent activation of enzyme activity following pre-treatment with eserine.