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Biomedical subjects

T Eisner

Publications and source records attributed to T Eisner.

At least 55 records · Page 3Linked to original sources
PubMed1996

Sodium: a male moth's gift to its offspring.

Males of the moth Gluphisia septentrionis acquire sodium by drinking from mud puddles. Analyses of male and female bodies indicate that such "puddling" behavior enables the male to provide his mate with a nuptial gift of sodium, presumably via the spermatophore. This gift (about 10 microg), amounting to more than half of a puddler male's total body sodium, is in large measure apportioned by the female to her eggs. Puddler-sired eggs contain 2 to 4 times more sodium than those control-sired; this difference is already apparent in eggs laid the night after mating. Paternal endowment of offspring with sodium had not previously been demonstrated for an insect to our knowledge. The potential adaptive significance of such chemical bestowal is evident, given that the foliar diet of G. septentrionis larvae is extremely low in sodium content.

Journal Article↗
PubMed1995

Sodium uptake by puddling in a moth.

Male Lepidoptera commonly visit stands of water to drink, a behavior known as puddling. Males of the notodontid moth Gluphisia septentrionis routinely puddle for hours, imbibing hundreds of gut-loads and voiding the fluid as repetitive anal jets. Cationic analyses showed puddling to lead to systemic sodium gain, a potential benefit to Gluphisia, whose larval food plant is low in sodium. Male Gluphisia are specialized for puddling, possessing a wide oral slit and a highly expanded enteric surface. The acquired sodium is transferred to the female at mating, for eventual incorporation into the eggs. Sodium acquisition may be the primary function of puddling in Lepidoptera.

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↗
PubMed1995

The chemistry of sexual selection.

The moth Utetheisa ornatrix (Lepidoptera: Arctiidae) is protected against predation by pyrrolizidine alkaloids that it sequesters as a larva from its foodplants. At mating, the male transfers alkaloid to the female with the spermatophore, a gift that the female supplements with alkaloid of her own and transmits to the eggs. Eggs are protected as a result. The male produces a pheromone, hydroxydanaidal, that he derives from the alkaloid and emits from a pair of extrusible brushes (coremata) during precopulatory interaction with the female. Males rendered experimentally alkaloid-free fail to produce the pheromone and are less successful in courtship. The male produces the pheromone in proportion both to his alkaloid load and to the amount of alkaloid he transfers to the female. The pheromone could thus serve as an indication of male "worth" and provide a basis for female choice. Utetheisa females are promiscuous and therefore are able to accrue multiple nuptial gifts (alkaloid and nutrient, both transmitted with the spermatophore). They use sperm selectively, favoring those of larger males. Larger males in nature are also richer in alkaloid. Females therefore reinforce after copulation the choice mechanism they already exercise during courtship.

Alkaloids↗
PubMed1995

Crohn's disease and colorectal carcinoma: rectal cancer complicating longstanding active perianal disease.

OBJECTIVES: Reports of Crohn's disease (CD)-associated colorectal carcinoma are being cited in the medical literature with increasing frequency. Our aim was to identify subgroups of patients with risk factors that may account for this. METHODS: We reviewed the medical records of 16 patients with the simultaneous diagnosis of CD and colorectal carcinoma and, in addition, reviewed previously reported cases of CD-associated colorectal carcinoma. RESULTS: Eight male and eight female patients presented with 18 carcinomas: four right colon, four transverse, two descending colon, and eight rectal lesions. Median age at presentation was 48 yr. The mean duration of CD before presentation of carcinoma was 19.7 yr. Two lesions were discovered in strictured bowel segments. Two patients had multiple cancers. One had simultaneous cecal and left colon adenocarcinomas. The other underwent resection of a right colon lesion and 5 yr later presented with transverse colon carcinoma. Eight patients had rectal cancer; all were diagnosed preoperatively. Six of these patients had a history of severe perianal CD. Six had undergone multiple incision and drainage procedures for perirectal abscesses and fistulas. Two developed malignancies in defunctionalized rectal stumps. One of these patients presented with simultaneous squamous rectal carcinoma and papillary bile duct cholangiocarcinoma. CONCLUSIONS: Gastrointestinal malignancy in association with CD has been reported. Symptoms of chronic inflammatory disease may obscure clinical manifestations of occult malignancy and thereby delay diagnosis. Crohn's patients with long-standing anorectal or perianal disease and stricture may well warrant surveillance endoscopy and biopsy of involved areas with the hope of earlier detection and treatment of these rectal cancers.

Adult↗
PubMed1994

Biosynthesis of a defensive insect alkaloid: epilachnene from oleic acid and serine.

The biosynthesis of the azamacrolide epilachnene by the coccinellid beetle Epilachna varivestis has been studied with 2H-labeled oleic acid, 2H-labeled L-serine, and 13C,15N-labeled L-serine. The incorporation of these precursors into epilachnene defines the origin of the alkaloid's entire carbon/nitrogen skeleton. GC/MS and GC/IR studies of alkaloid produced by Epilachna fed with deuteriated oleic acid show that oleic acid loses four carbon atoms from its carboxyl end during the biosynthesis. Other details, including the mechanism of carbon-nitrogen bond formation between the fatty acid and amino acid moieties, remain to be established.

Alkaloids↗
PubMed1994

Spermatophore size as determinant of paternity in an arctiid moth (Utetheisa ornatrix).

Female Utetheisa ornatrix exercise postcopulatory mate selection, favoring sperm of larger males. Larger males also produce larger spermatophores, raising the question whether males are selected on the basis of body size or the size of their spermatophore. We here present evidence, based on matings in which males were induced to deliver spermatophores disproportionate in size to body mass, that the determinant is spermatophore mass.

Animals↗
PubMed1994

Defensive use of an acquired substance (carminic acid) by predaceous insect larvae.

Larvae of two insects, a coccinellid beetle (Hyperaspis trifurcata) and a chamaemyiid fly (Leucopis sp.), feed on cochineal insects and appropriate their prey's defensive chemical, carminic acid, for protective purposes of their own. H. trifurcata discharges the chemical with droplets of blood (hemolymph) that it emits when disturbed; Leucopis sp. ejects the compound with rectal fluid. Ants are thwarted by these defenses, which are compared with the previously-described defense of a pyralid caterpillar (Laetilia coccidivora) that disgorges carminic acid-laden crop fluid. The defensive fluid of all three larvae contains carminic acid at concentrations spanning a range (0.2-6.2%) proven deterrent to ants. Many insects are known to appropriate defensive substances from plants. Insects that acquire defensive chemicals from animal sources may be relatively rare.

Animals↗
PubMed1993

Relevance of chemistry to conservation of isolated populations: the case of volatile leaf components of Dicerandra mints.

Chemical analysis of the essential oils of four congeneric species of mint plant (Dicerandra spp.) endemic to Florida revealed a pattern of chemical similarity and dissimilarity that would not have been predicted on morphological or geographic criteria. Dicerandra christmanii differs fundamentally from its congeners in that it produces fewer compounds and lacks the acyclic components. Yet D. christmanii is more closely similar to Dicerandra frutescens than to other Dicerandra species in morphological characters and geographic range. We conclude that the potential chemical value of a species should not be prejudged on the basis of nonchemical characters and that designation of surplus plant populations by conservationists should be resisted unless such populations have also been chemically studied.

Conservation of Natural Resources↗
PubMed1993

Circumvention of prey defense by a predator: ant lion vs. ant.

The pit-dwelling ant lion Myrmeleon carolinus, although topically sensitive to formic acid, is able to prey on formic acid-spraying ants (Camponotus floridanus). It kills the ants without inducing them to spray, and it sucks out the ant's body contents without puncturing the acid sac. Ordinarily, when Camponotus is attacked it retaliates by simultaneously biting and spraying, but it usually refrains from spraying until it has secured a grip with the mandibles. When Myrmeleon pulls Camponotus into the sand at the bottom of the pit, the ant is seemingly unable to grasp the ant lion and it is killed without being induced to spray. When feeding on the ant, the ant lion sucks up the contents of the nutrient-laden crop. How the ant lion differentiates between crop and acid sac, managing to spare the latter while rupturing the former, remains unknown.

Journal Article↗
PubMed1993

Insect pheromone biosynthesis: stereochemical pathway of hydroxydanaidal production from alkaloidal precursors in Creatonotos transiens (Lepidoptera, Arctiidae).

The mechanism by which the moth Creatonotos transiens produces its male pheromone, (7R)-hydroxydanaidal, from heliotrine, an alkaloidal precursor of opposite (7S) stereochemistry, was investigated. Specifically deuteriated samples of heliotrine and epiheliotrine were prepared and fed to C. transiens larvae, and the steps in the biosynthetic process were monitored by gas chromatography/mass spectrometry. These analyses indicate that heliotrine is initially epimerized to (7S)-epiheliotrine by oxidation to the corresponding ketone followed by stereospecific reduction. The order of the subsequent steps is (i) aromatization of the dihydropyrrole ring, (ii) ester hydrolysis, and (iii) oxidation of the resulting primary alcohol to the final aldehyde. The ecological implications of this insect's ability (and the inability of another moth, Utetheisa ornatrix) to use representatives of two stereochemical families of alkaloids as pheromone precursors are discussed.

Journal Article↗
PubMed1993

Azamacrolides: a family of alkaloids from the pupal defensive secretion of a ladybird beetle (Epilachna varivestis).

Defensive droplets from glandular hairs of the pupa of the Mexican bean beetle, Epilachna varivestis, contain a group of structurally novel alkaloids, the azamacrolides. The major constituent of this secretion, epilachnene, is shown to be (5Z)-11-propyl-12-azacyclotetradec-5-en-14-olide. The secretion also contains an epilachnadiene and trace amounts of three closely related components.

Alkaloids↗
PubMed1993

Postcopulatory sexual selection in an arctiid moth (Utetheisa ornatrix).

The offspring of twice-mated female Utetheisa ornatrix show low incidence of mixed paternity. Most progeny are sired exclusively by one male, the larger one, irrespective of parental age, male pyrrolizidine alkaloid content, mating order, between-mating interval, or duration of copulation. Data are presented suggesting that the female herself may exert control over the process by which one set of sperm is utilized at the expense of the other. Evidence for such postcopulatory female choice of sperm had not previously been obtained for an insect. Promiscuity provides the female with a means for accruing nuptial gifts (nutrients, defensive alkaloids). Sperm selection provides her with the option of utilizing sperm from larger, potentially more fit, males.

Animals↗
PubMed1993

Pregnanes from defensive glands of a belostomatid bug.

The aquatic bug Abedus herberti (Hemiptera: Belostomatidae) secretes a mixture containing four pregnanes (desoxycorticosterone (I), pregnenolone (II), progesterone (III), and 3 alpha-hydroxy-pregn-5-en-20-one (IV)) from its cephalic glands. Pregnanes had previously been characterized from the defensive glands of aquatic beetles (Dytiscidae) and shown to be deterrent to fish. It may be specifically under predation pressure from fish that A. herberti and Dytiscidae evolved their comparable defenses.

Animals↗
PubMed1993

Defensive secretion of the millipede Floridobolus penneri.

Six quinones were identified from the defensive secretion of the millipede Floridobolus penneri. The two major components, 2-methyl-1,4-benzoquinone [1] and 2-methoxy-3-methyl-1,4-benzoquinone [3], previously characterized, comprise 95% of the secretion. One of the minor compounds, 2,5-dimethyl-3-methoxy-1,4-benzoquinone [4], is a new natural product. Another, 2-hydroxy-3-methyl-1,4-benzoquinone [2], had been tentatively characterized from a microbial source. The other two components are 2,3-dimethoxy-1,4-benzoquinone [5] and 2,3-dimethoxy-5-methyl-1,4-benzoquinone [6]. No sex difference in the composition of the secretion was noted.

Animals↗