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Biomedical subjects

A B Borkovec

Publications and source records attributed to A B Borkovec.

At least 19 recordsLinked to original sources
PubMed1990

Conversion of 3-dehydroecdysone by a ketoreductase in post-diapause, pre-hatch eggs of the gypsy moth Lymantria dispar.

The prothoracic glands (PGs) of Lymantria dispar (day-5 female, last-stage larvae) produce both ecdysone and an ecdysteroid which has the same retention time on reverse-phase liquid chromatography (RPLC) as a known standard of 3-dehydroecdysone. The latter ecdysteroid can be converted by a heat-labile factor in extracts of post-diapause, pre-hatch L. dispar eggs to an ecdysteroid which has the same retention time on RPLC as ecdysone. Purified 3-dehydroecdysone, similarly treated with egg extract, also gives the same retention time on RPLC as ecdysone. Taken together, these data suggest that, like Manduca sexta, a major product of the PGs in L. dispar is 3-dehydroecdysone. Furthermore, these data suggest that L. dispar eggs, which contain mature embryos, possess ecdysteroid ketoreductase activity capable of converting 3-dehydroecdysone to ecdysone. This is the first report of ecdysteroid ketoreductase activity in embryonated eggs.

3-Hydroxysteroid Dehydrogenases↗
PubMed1986

The pharate adult clasper as a tool for measuring chitin synthesis and for identifying new chitin synthesis inhibitors.

A rapid, reliable, repeatable bioassay for measuring chitin synthesis is described. It utilizes the clasper from male pharate adult European corn borers and measures the incorporation of [14C]N-acetylglucosamine. Chitin synthesis is maximum in claspers taken from animals 5 and 6 days postpupation. The system is very sensitive to inhibition by the phenylbenzoyl ureas and polyoxins and should be useful for identifying potential inhibitory agents.

Acetylglucosamine↗
PubMed1983

Partial purification of egg development neurosecretory hormone with reverse-phase liquid chromatographic techniques.

We report the use of reverse-phase liquid chromatographic techniques for the isolation of a steroidogenic neuropeptide (EDNH) from mosquito heads. Activity of fractions was assayed by measuring the ability of ovaries to produce ecdysteroid in vitro. Dose response profiles using crude head extracts or partially purified EDNH were nearly identical, indicating that the methods of preparation did not alter biological activity. EDNH activity eluted from a reverse-phase HPLC (RP-HPLC) column primarily near 35 percent acetonitrile using a linear gradient. Methods developed with an analytical RP-HPLC column were successfully adapted for preparative work. Active fractions from the preparative RP-HPLC were further purified on a second analytical column under isocratic conditions at 30% acetonitrile. Two adjacent UV absorbing peaks were found, each with EDNH activity. Activity was sensitive to proteolysis.

Aedes↗
PubMed1976

Control and management of insect populations by chemosterilants.

Chemosterilants, i.e., chemical compounds that interfere with the reproduction potential of sexually reproducing organisms, can be used in three new approaches to insect control. In the sterile-insect release technique, the principal problem is to develop compounds and methods for their application that would not result in introducing harmful residues into the environment. Because of the unusual and often unique circumstances connected with releasing large numbers of sterilized insects, the residue problem and its cost-benefit aspects must be examined individually for each intended control or eradication program. In the direct application technique, chemosterilants must meet the same efficiency and safety standards required from approved insecticides. Combined insecticidal and sterilizing activity is characteristic for some compounds now being investigated. In the genetic technique, chemosterilants may be used for inducing heritable changes in the insect's genome under laboratory conditions, and such procedures would not present any residue problems. Only the first two chemosterilant techniques are approaching practical application, and their safety aspects require detailed evaluation and assessment.

Chemosterilants↗
PubMed1975

Control of insects by sexual sterilization.

The control of insect populations by restricting their birth rate offers several advantages over methods based on increasing the death rate. The sterile-male technique scored practical success in the control of the screwworm, Cochliomyia hominivorax (Coquerel), but more general applications of the sterility procedure may be expected in conjunction with the development of integrated procedures for pest insect management.

Animals↗