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Biomedical subjects

J Meinwald

Publications and source records attributed to J Meinwald.

At least 37 records · Page 2Linked to original sources
PubMed1998

Rendering the inedible edible: circumvention of a millipede's chemical defense by a predaceous beetle larva.

The larva of the phengodid beetle, Phengodes laticollis, feeds on the millipede, Floridobolus penneri, without risking exposure to the repellent benzoquinones ordinarily ejected by the millipede from its defensive glands when attacked. The phengodid subdues the millipede by piercing the millipede's integument with its hollow sickle-shaped mandibles and apparently injecting gastric fluid. The infusion abruptly paralyzes the millipede, which thereby is prevented from discharging its glands. As the phengodid then imbibes the liquefied systemic contents of the dead millipede, the millipede's benzoquinones remain harmlessly confined to the glands, prevented from diffusing into the millipede's body cavity by the glands' impervious cuticular lining. At the end of the meal only the millipede's skeletal armor and glandular sacs remain uneaten. Analysis of such discarded sacs showed these to contain benzoquinones in amounts commensurate with those present in replete glands of living millipedes.

Animals↗
PubMed1998

Chilocorine C: a new "dimeric" alkaloid from a coccinellid beetle, Chilocorus cacti.

A new hexacyclic alkaloid, chilocorine C (4), has been isolated from Chilocorus cacti and characterized on the basis of its IR, UV, MS, and NMR data. Although its structure is closely related to that of exochomine (1) (isolated from Exochomus quadripustulatus) and to chilocorine A (2) and B (3) (obtained previously from C. cacti), the presence of a hydroxymethyl substituent on the saturated tricyclic moiety represents an unexpected structural variation on the dimeric alkaloid theme.

Animals↗
PubMed1997

Firefly "femmes fatales" acquire defensive steroids (lucibufagins) from their firefly prey.

Female fireflies of the genus Photuris, the so-called firefly "femmes fatales," prey on male fireflies of the genus Photinus. The females are able to entrap the males by faking the flash signal characteristics of the Photinus female. We found that by feeding on Photinus males, Photuris females gain more than nutrients. They also acquire defensive steroidal pyrones called lucibufagins, which are contained in Photinus but which Photuris fireflies are unable to produce on their own. Photuris females that eat Photinus males or lucibufagin are rejected by Phidippus jumping spiders. Lucibufagin itself proved to be a deterrent to such spiders. Field-collected Photuris females contain lucibufagin in varying amounts. The more lucibufagin they contain the more unacceptable they are to Phidippus.

Animals↗
PubMed1997

Defensive production of formic acid (80%) by a carabid beetle (Galerita lecontei).

The carabid beetle Galerita lecontei has a pair of abdominal defensive glands that secrete a mixture of formic acid, acetic acid, and lipophilic components (long-chain hydrocarbons and esters). Formic acid, at the concentration of 80%, is the principal constituent. The beetle ejects the secretion as a spray, which it aims accurately toward parts of the body subjected to assault. At full capacity, the glands store 4.5 mg of formic acid (3% of body mass), enough for upward of six ejections. The beetle reloads the glands at a rate of 126 microg of formic acid per day. For the approximately 500 secretory cells of the glands, this means an hourly output of 10 ng of formic acid per cell, or about 5% of cell volume. Replenishing empty glands to their full formic acid load takes the beetle an estimated 37 days. Replenishing the 0.7 mg of formic acid expended in a single discharge takes 5.5 days.

Animals↗
PubMed1997

Pyrrolidinoöxazolidine alkaloids from two species of ladybird beetles.

From the mixture of alkaloids obtained from adults of two species of ladybird beetles, Epilachna varivestis and Epilachna borealis, a novel bicyclic alkaloid, 5-(12'-aminotridecyl)pyrrolidinoöxazolidine [(5 alpha, 7 a beta)-hexahydro-alpha-methylpyrrolo[2,1-b]oxazole-5-dodecaneami ne] (2) was characterized on the basis of spectrometric and synthetic investigations. This new alkaloid is related structurally to a monocyclic congener 1-(2-hydroxyethyl)-2-(12'-aminotridecyl)pyrrolidine (1), previously characterized from E. varivestis. Two additional alkaloids (lower homologs of 1 and 2) from E. borealis were characterized as 5-(10'-aminoündecyl)pyrrolidinoöxazolidine [(5 alpha,-7 a beta)-hexahydro-alpha-methylpyrrolo[2,1-b]oxazole-5-decaneamine ] (7) and 1-(2-hydroxyethyl)-2-(10'-aminoündecyl)pyrrolidine (8), on the basis of their mass spectra.

Alkaloids↗
PubMed1997

Defensive production of quinoline by a phasmid insect (Oreophoetes peruana).

Adults and nymphs of the Peruvian stick insect Oreophoetes peruana (order Phasmatodea) have a pair of thoracic glands from which they discharge a malodorous fluid when disturbed. The secretion contains a single volatile component, quinoline. Quinoline has not been reported previously from an animal source. The compound proved repellent or topically irritant in assays with ants, spiders, cockroaches and frogs. O. peruana nymphs, at molting, do not extricate the shed cuticular lining of the glands, thereby managing not to lose their secretory supply when they cast their skin. They are able, as a consequence, to discharge secretion even while still teneral after molting.

Animals↗
PubMed1996

Chemical basis of courtship in a beetle (Neopyrochroa flabellata): cantharidin as precopulatory "enticing" agent.

Male Neopyrochroa flabellata have a natural affinity for cantharidin (Spanish fly). They are attracted to cantharidin baits in the field and feed on the compound if it is offered to them in the laboratory. Males that ingest cantharidin secrete cantharidin from a cephalic gland. Females sample secretion from this gland during courtship and mate preferentially with males that had fed on cantharidin. Cantharidin-unfed males can be rendered acceptable to females if cantharidin is added to their cephalic gland.

Animals↗
PubMed1996

Chemical basis of courtship in a beetle (Neopyrochroa flabellata): Cantharidin as "nuptial gift".

The amount of cantharidin (Spanish fly) that the Neopyrochroa flabellata male presents to the female as a glandular offering during courtship represents only a small fraction of the total cantharidin the male accumulates systemically following ingestion of the compound. A major fraction of the acquired cantharidin is stored by the male in the large accessory glands of the reproductive system. At mating, the male transfers this supply, presumably as part of the sperm package, to the spermatheca of the female. The female in turn allocates the gift to the eggs. Eggs endowed with cantharidin proved relatively invulnerable to attack by a predaceous beetle larva (Coleomegilla maculata).

Animals↗
PubMed1996

Tocopheryl acetates from the pupal exocrine secretion of the squash beetle, Epilachna borealis (Coccinellidae).

The oily droplets on the pupal integumental hairs of the squash beetle Epilachna borealis contain a mixture of alpha-, beta-, gamma-, and delta-tocopheryl acetates as major constituents. In addition, the secretion contains a number of minor components that appear to be dehydrocongeners of the major components. This is the first report of the occurrence of acetate esters of any tocopherol in nature.

Animals↗
PubMed1996

Chemical egg defense in a green lacewing (Ceraeochrysa smithi)

The green lacewing Ceraeochrysa smithi (Neuroptera, Chrysopidae), like other members of its family, lays its eggs on stalks, but it is unusual in that it coats these stalks with droplets of an oily fluid. The liquid consists of a mixture of fatty acids, an ester, and a series of straight-chain aldehydes. Relative to the eggs of a congeneric chrysopid that lacks stalk fluid, the eggs of C. smithi proved well protected against ants. Components of the fluid, in an assay with a cockroach, proved potently irritant. Following emergence from the egg, C. smithi larvae imbibe the stalk fluid, thereby possibly deriving nutritive benefit, defensive advantage, or both.

Aldehydes↗
PubMed1996

Assignment of absolute stereochemistry to an insect pheromone by chiral amplification.

Chiral amplification, a new strategy for determining the absolute configuration of difficulty available natural secondary alcohols or analogous amines, is described. Using this technique, the R configuration can be assigned to both components of the male sex pheromone emitted by the longhorn beetle, Anaglyptus subfasciatus. The application of this approach to fourteen alcohols and four amines illustrates its scope and limitations.

Acylation↗
PubMed1996

(3E,8Z,11Z)-3,8,11-tetradecatrienyl acetate, major sex pheromone component of the tomato pest Scrobipalpuloides absoluta (Lepidoptera: Gelechiidae).

The major sex attractant emitted by Scrobipalpuloides absoluta females is shown to be (3E,8Z,11Z)-3,8,11-tetradecatrien-1-yl acetate by a novel strategy involving the random reduction of double bonds, followed by methylthiolation of the reduced products. Each female sex gland contains ca. 1-5 ng of this pheromone. This triene ester, synthesized by a stereospecific procedure, shows spectral and gas chromatographic properties identical to those of the natural substance. In field tests and wind tunnel bioassays, the synthetic ester was found to be highly attractive to conspecific males. The male response to this pheromone, however, is restricted to the same early-morning time window during which females exhibit calling behavior.

Acetates↗
PubMed1995

Application of chiral gas chromatography with electroantennographic detection to the determination of the stereochemistry of a cockroach sex pheromone.

The coupling of an electroantennographic detector to a chiral capillary gas chromatographic system provides a highly sensitive technique for the determination of pheromone stereochemistry. Electronic modification of the usual electroantennographic detector enables the detector to respond to the relatively broad peaks produced by chiral gas chromatographic systems. By using this methodology, supellapyrone, a female sex pheromone of the brownbanded cockroach Supella longipalpa (Orthoptera: Blattellidae), is shown to be 5-(2'R,4'R-dimethylheptanyl)-3-methyl-2H-pyran-2-one.

Animals↗
PubMed1995

Structure, stereochemistry, and thermal isomerization of the male sex pheromone of the longhorn beetle Anaglyptus subfasciatus.

Male-released sex pheromone constituents of the longhorn beetle Anaglyptus subfasciatus (Coleoptera: Cerambycidae) are identified by GC-MS and GC-Fourier transform infrared as a 7:1 molar mixture of 3-hydroxy-2-hexanone and 3-hydroxy-2-octanone. These two compounds undergo thermal isomerization during GC analyses to give the corresponding 2-hydroxy-3-alkanones. Comparison of GC retention times of the natural products with those of synthesized enantiomerically pure compounds revealed that both semiochemicals have (R)-stereochemistry. These absolute configurations were confirmed by comparisons of the (R)-methoxy(trifluoromethyl)phenylacetic acid esters of insect-derived and synthetic samples.

Animals↗
PubMed1995

The chemistry of phyletic dominance.

Studies of arthropod defensive chemistry continue to bring to light novel structures and unanticipated biosynthetic capabilities. Insect alkaloids, such as the heptacyclic acetogenin chilocorine and the azamacrolides, exemplify both of these aspects of arthropod chemistry. Spider venoms are proving to be rich sources of neuroactive components of potential medical interest. The venom of a fishing spider, Dolomedes okefinokensis, has yielded a polyamine which reversibly blocks L- and R-type voltage-sensitive calcium channels. Most recently, we have characterized, from the funnel-web spider Hololena curta, a sulfated nucleoside glycoside which serves as a reversible blocker of glutamate-sensitive calcium channels. The ability to synthesize or acquire an extremely diverse array of compounds for defense, offense, and communication appears to have contributed significantly to the dominant position that insects and other arthropods have attained.

Animals↗