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Biomedical subjects

A Cork

Publications and source records attributed to A Cork.

At least 19 recordsLinked to original sources

Identification of components of male-produced pheromone of coffee white stemborer, Xylotrechus quadripes.

The coffee white stem borer, Xylotrechus quadripes Chevrolat (Coleoptera: Cerambycidae), is the foremost pest of arabica coffee in India, Sri Lanka, China, Vietnam, and Thailand. Previous work showed that female beetles were attracted to traps baited with male beetles. Analyses of volatiles from male X. quadripes of Indian origin by gas chromatography (GC) linked to electroantennographic (EAG) recording from a female beetle antenna showed three male-specific components comprising more than 90% of the volatiles, two of which elicited EAG responses. The major EAG-active component was produced at up to 2 microg hr(-1) insect(-1) and was identified as (S)-2-hydroxy-3-decanone (I) by comparison of GC data, and mass (MS), infrared, and nuclear magnetic resonance (NMR) spectra with those of synthetic standards. The second component was identified as 3-hydroxy-2-decanone (II) produced in part by isomerization of I under the conditions of the GC analysis, although the NMR spectrum suggested it is naturally produced at up to 7% of I. The minor component that elicited an EAG response, present at 7% of the amount of I, was identified as (S,S)-2,3-dihydroxyoctane (III) from GC and MS data. 2-Hydroxy-3-octanone (0.2-0.5% of I), 2,3-decanedione (2% of I), 2-phenylethanol (3% of I), and octanoic acid (4% of I) were also identified in volatiles from male beetles. A general, stereospecific synthetic route to the enantiomers of 2-hydroxy-3-alkanones from the enantiomers of ethyl lactate was developed. The enantiomers of III were synthesized from (E)-2-octene by Sharpless asymmetric dihydroxylation. (S)-(I) was attractive to male X. quadripes in laboratory bioassays, but addition of (S,RS)-(III) at 10% of I reduced attractiveness. In field trials carried out in India with sticky, cross-vane traps, (S)- and (RS)-(I) attracted male X. quadripes and addition of (S,S)-(III) at 10% of I reduced attractiveness. Significant numbers of female Demonax balyi Pascoe (Coleoptera: Cerambycidae) were sometimes caught in traps baited with (S)-(I) alone.

Animals↗

Development of mass trapping technique for control of brinjal shoot and fruit borer, Leucinodes orbonalis (Lepidoptera: Pyralidae).

Locally-produced clear plastic water traps (12 cm x 14 cm base and 21 cm height) were optimized for use in large-scale mass trapping trials for control of brinjal fruit and shoot borer, Leucinodes orbonalis Guenée. Changing the shape (square and triangular) and number (two and four) of entry holes in the water trap had no significant effect on trap catch. Significantly more male moths were caught in traps treated with water containing powdered detergent than liquid detergent, light gear oil or insecticide. All water traps tested caught significantly higher numbers of moths than sticky delta traps with open sides under farmers' field conditions. Trap catches per 100 m2 were found to increase with increasing number of traps from 3 to 6 but the difference in catch between 4 and 6 traps per 100 m2 was not significant. Two small-scale replicated integrated pest management (IPM) trials were conducted consisting of the optimized water trap placed out with 10 m spacing (4 per 100 m2) and infested shoots pruned and destroyed. The first season trial had two treatments, IPM and farmers' practice in which farmers applied insecticide every two days in the peak harvest period. Overall, the percentage of healthy fruit and yields in both treatments were comparable at 53.8 and 49.6% and 20 and 19.4 tonnes per ha in the IPM and farmers' practice plots respectively. However, the initial infestations in the IPM plots (68%) were significantly higher than in farmers' practice plots (16%) due to the proximity of the nurseries used for the IPM plots to stacks of brinjal crop residues from the previous season that acted as a source of infestation. The second season's trials contained a third treatment in which IPM and farmers' practice were combined. The percent total healthy fruits harvested were 46.1, 58.6 and 69.1% respectively for the farmers' practice, farmers' practice plus IPM and IPM alone. Averaged total fruit yields were approximately 12 tonnes per ha for the farmers' practice plots and 30 tonnes per ha for each of the IPM-treated plots. The IPM plot had significantly fewer infested fruit than the IPM plus farmers practice plots and this was attributed to the activity of the larval parasitoid Trathala flavo-orbitalis (Cameron) that was suppressed in trial plots treated with insecticides.

Animals↗

Minor components in the sex pheromone of legume podborer: Maruca vitrata development of an attractive blend.

The legume podborer, Maruca vitrata (syn. M. testulalis) (F.) (Lepidoptera: Pyralidae) is a pantropical pest of legume crops. Sex pheromone was collected by gland extraction or trapping of volatiles from virgin female moths originating in India, West Africa, or Taiwan. Analysis by GC-EAG and GC-MS confirmed previously published findings that (E,E)-10,12-hexadecadienal is the most abundant EAG-active component with 2-5% of (E,E)-10,12-hexadecadienol also present. At least one other EAG response was detected at retention times typical of monounsaturated hexadecenals or tetradecenyl acetates, but neither could be detected by GC-MS. Laboratory wind-tunnel bioassays and a field bioassay of blends of (E,E)-10,12-hexadecadienal with (E,E )-10,12-hexadecadienol and a range of monounsaturated hexadecenal and tetradecenyl acetate isomers indicated greatest attraction of males was to those including (E,E)-10,12-hexadecadienol and (E)-10-hexadecenal as minor components. In subsequent trapping experiments in cowpea fields in Benin, traps baited with a three-component blend of (E,E)-10,12-hexadecadienal and these two minor components in a 100:5:5 ratio caught significantly more males than traps baited with the major component alone, either two-component blend, or virgin female moths. Further blend optimization experiments did not produce a more attractive blend. No significant differences in catches were found between traps baited with polyethylene vials or rubber septa, or between lures containing 0.01 and 0.1 mg of synthetic pheromone. Significant numbers of female M. vitrata moths, up to 50% of total catches, were trapped with synthetic blends but not with virgin females. At present there is no clear explanation for this almost unprecedented finding, but the phenomenon may improve the predictive power of traps for population monitoring.

Animals↗

Female sex pheromone of brinjal fruit and shoot borer, Leucinodes orbonalis (Lepidoptera: Pyralidae): trap optimization and application in IPM trials.

Delta and wing traps baited with synthetic female sex pheromone of Leucinodes orbonalis Guenée were found to catch and retain ten times more moths than either Spodoptera or uni-trap designs. Locally-produced water and funnel traps were as effective as delta traps, although 'windows' cut in the side panels of delta traps significantly increased trap catch from 0.4 to 2.3 moths per trap per night. Trap catch was found to be proportional to the radius of sticky disc traps in the range 5-20 cm radius, discs with a 2.5 cm radius caught no moths. Wing traps placed at crop height caught significantly more moths than traps placed 0.5 m above or below the crop canopy. Replicated integrated pest management (IPM) trials (3 x 0.5 ha per treatment) were conducted in farmers fields with young and mature eggplant crops. Farmers applied insecticides at least three times a week in all check and IPM plots. In addition pheromone traps were placed out at a density of 100 per ha and infested shoots removed weekly in the 0.5 ha IPM plots. Pheromone trap catches were reduced significantly from 2.0 to 0.4 moths per trap per night respectively in check and IPM plots in a young crop and 1.1 to 0.3 moths per trap per night in check and IPM plots respectively in a mature crop. Fruit damage was significantly reduced from an average of 41.8% and 51.2% in check plots of young and mature crops respectively to 22% and 26.4 respectively in the associated IPM plots. Significant differences in pheromone trap catches and fruit damage were attained four and two weeks respectively after IPM treatments began in the mature crop whereas in the immature crop significant differences were not observed for the first eight to nine weeks respectively. The relative impact of removing infested shoots and mass trapping on L. orbonalis larval populations was not established in these trials but in both cases there was an estimated increase of approximately 50% in marketable fruit obtained by the combination of control techniques compared to insecticide treatment alone.

Animals↗

Landing responses of Anopheles gambiae elicited by oxocarboxylic acids.

A wind tunnel bioassay and video system were used to observe Anopheles gambiae Giles sensu stricto (Diptera: Culicidae) landing on glass cylinders, heated to human skin temperature (34 degrees C) and treated with aqueous solutions of oxocarboxylic acids. Six of nine compounds tested: 2-oxobutanoic, 2-oxo-3-methylbutanoic, 2-oxopentanoic, 2-oxo-3-methylpentanoic, 2-oxo-4-methylpentanoic and 2-oxohexanoic elicited significant landing responses in comparison to a water control. Landing responses appeared to be restricted to C4-C6, 2-oxocarboxylic acids. A solution of 1 microg/microL of 2-oxopentanoic acid elicited the highest level of response that was temperature dependent: significant numbers of landings occurred only within +/-2 degrees C of human skin temperature. Chemical analysis by linked gas-liquid chromatography/mass spectrometry of methyl-oxime, trimethylsilyl derivatized samples of human sweat extracts revealed the presence of 2-oxopropanoic (pyruvic) acid and three behaviourally active, branched chain acids: 2-oxo-3-methylbutanoic, 2-oxo-3-methylpentanoic and 2-oxo-4-methylpentanoic.

Animals↗

Morphology of rsw1, a cellulose-deficient mutant of Arabidopsis thaliana.

The rsw1 mutant of Arabidopsis thaliana is mutated in a gene encoding a cellulose synthase catalytic subunit. Mutant seedlings produce almost as much cellulose as the wild type at 21 degrees C but only about half as much as the wild type at 31 degrees C. We used this conditional phenotype to investigate how reduced cellulose production affects growth and morphogenesis in various parts of the plant. Roots swell in all tissues at 31 degrees C, and temperature changes can repeatedly switch them between swollen and slender growth patterns. Dark-grown hypocotyls also swell, whereas cotyledons and rosette leaf blades are smaller, their surfaces are more irregular and their petioles shorter. Leaf trichomes swell and branch abnormally. Plants readily initiate inflorescences at 31 degrees C which have shorter but not fatter bolts and stomata which bulge above the uneven surface of internodes. Bolts carry the normal number of flowers, but their stigmas protrude beyond the shortened sepals and petals. Anthers dehisce normally, but self-fertilisation is reduced because the stigma is well above the anthers. Anther filaments are short and show a crumpled surface. Viable pollen develops, but female reproductive competence and postpollination development are severely impaired. We conclude that the RSW1 gene is important for cellulose synthesis in many parts of the plant and that reduced cellulose synthesis suppresses organ expansion rather than organ initiation, causes radial swelling only in the root and hypocotyl, but makes the surfaces of many organs uneven. We discuss some possible reasons to explain why different organs vary in their responses. The morphological changes suggest that RSW1 contributes cellulose to primary walls but do not yet exclude a role during secondary-wall deposition.

Arabidopsis↗

Electrophysiological responses of female Helicoverpa armigera (Hübner) (Lepidoptera; Noctuidae) to synthetic host odours.

Studies were conducted to investigate the electroantennographic (EAG) responses of adult female Helicoverpa armigera to a range of known and putative kairomone components. The studies show that at a given dose the EAG responses elicited by a series of straight-chain aliphatic primary alcohols were not dependent on volatility since butan-1-ol and pentan-1-ol elicited EAG responses that were significantly smaller than those elicited by hexan-1-ol. The amplitudes of responses to hexan-1-ol were found to be dose dependent with a dose of 10(-1) µmol at source in a non-volatile solvent eliciting the largest response. Similarly, changes in functionality in a range of C(6) straight-chain aliphatic compounds significantly changed the amplitude of response elicited, with aldehydes eliciting smaller responses than the related primary alcohols and saturated compounds eliciting higher responses than related unsaturated compounds. Of the range of nine host plant-produced terpenoids tested, ocimene and beta-phellandrene elicited the highest responses and of the six aromatic compounds tested phenylacetaldehyde and benzaldehyde elicited the largest responses, at the doses tested. The significance of these findings for analysis of floral odours by gas chromatography linked to electroantennography as a means of identifying kairomone components attractive to H. armigera are discussed.

Journal Article↗

Electrophysiological and behavioral responses of female Helicoverpa armigera to compounds identified in flowers of African marigold, Tagetes erecta.

Seven electrophysiologically active compounds were detected in air-entrained headspace samples of live flowers of Tagetes erecta analyzed by gas chromatography (GC) linked to a female Helicoverpa armigera electroantennograph (EAG) using polar and nonpolar capillary columns. These compounds were subsequently identified using GC linked to mass spectrometry as benzaldehyde, (S)-(-)-limonene, (R,S)-(+/-)-linalool, (E)-myroxide, (Z)-beta-ocimene, phenylacetaldehyde, and (R)-(-)-piperitone. Electrophysiological activity was confirmed by EAG with a 1-microg dose of each compound on filter paper eliciting EAG responses that were significantly greater than the solvent control response from female moths. Wind-tunnel bioassays with T. erecta headspace samples, equivalent to 0.4 flower/hr emission from a live flower, elicited a significant increase in the number of upwind approaches from female H. armigera relative to a solvent control. Similarly, a seven-component synthetic blend of EAG-active compounds identified from T. erecta presented in the same ratio (1.0:1.6:0.7:1.4:0.4:5.0:2.7, respectively) and concentration (7.2 microg) as found in the natural sample elicited a significant increase in the number of upwind approaches relative to a solvent control during a 12-min bioassay that was equivalent to that elicited by the natural T. erecta floral volatiles.

Air Movements↗

Female sex pheromone of brinjal fruit and shoot borer, Leucinodes orbonalis blend optimization.

The brinjal fruit and shoot borer, Leucinodes orbonalis is the major pest of eggplant in South Asia. Analysis of female pheromone gland extracts prepared from insects of Indian and Taiwanese origin confirmed (E)-11-hexadecenyl acetate (E11-16:Ac) as the major pheromone component with 0.8 to 2.8% of the related (E)-11-hexadecen-1-ol (E11-16:OH), as previously reported from Sri Lanka. The average quantity of E11-16:Ac extracted per female was estimated to be 33 ng, with a range of 18.9 to 46.4 ng when collected 2 to 3 hr into the scotophase. In field trials conducted in India, blends containing between 1 and 10% E11-16:OH caught more male L. orbonalis than E11-16:Ac alone. At the 1,000 microg dose, on white rubber septa, addition of 1% E11-16:OH to E11-16:Ac was found to be more attractive to male L. orbonalis than either 0.1 or 10% E11-16:OH. Trap catch was found to be positively correlated with pheromone release rate, with the highest dose tested, 3,000 microg, on white rubber septa catching more male moths than lower doses. Field and wind tunnel release rate studies confirmed that E11-16:OH released from white rubber septa and polyethylene vials at approximately twice the rate of E11-16:Ac and that the release rate of both compounds was doubled in polyethylene vials compared to white rubber septa. This difference in release rate was reflected in field trials conducted in Bangladesh where polyethylene vial dispensers caught more male moths than either black or white rubber septa, each loaded with the same 100:1 blend of E11-16:Ac and E11-16:OH in a 3,000 microg loading.

Animals↗

Electrophysiological responses of antennal receptor neurons in female Australian sheep blowflies, Lucilia cuprina, to host odours.

Studies were conducted to investigate the electrophysiological responses of receptor neurons on the antennae of female Lucilia cuprina to putative stimulants. Three distinct types of olfactory neurons were identified. Tests with 25 compounds showed 27 out of the 75 neurons examined responded best to racemic 1-octen-3-ol (Oct-best neuron), nine to dimethyldisulphide (DMDS-best neuron) and seven to 2-phenylethanol (PE-best neuron). The remaining cells were not stimulated by any chemical stimulus presented in this study. The olfactory neurons showed low spontaneous activities, 2.2 ~ 2.7 impulses/s, which increased significantly on stimulation with test compounds. Dose-dependent responses were observed with Oct-best neurons. Another type of neuron that had a much higher spontaneous activity (26 impulses/s) was observed. This neuron did not respond to any of the candidate compounds tested but showed a decrease in activity with increased airflow over the antennae and was termed the Airflow-sensitive neuron. The spontaneous activities of Oct-, DMDS-, PE-best and Airflow-sensitive neurons were inhibited by butanoic, pentanoic, hexanoic acids, and 3-methylindole.

Journal Article↗

Molecular analysis of cellulose biosynthesis in Arabidopsis.

Cellulose, an abundant, crystalline polysaccharide, is central to plant morphogenesis and to many industries. Chemical and ultrastructural analyses together with map-based cloning indicate that the RSW1 locus of Arabidopsis encodes the catalytic subunit of cellulose synthase. The cloned gene complements the rsw1 mutant whose temperature-sensitive allele is changed in one amino acid. The mutant allele causes a specific reduction in cellulose synthesis, accumulation of noncrystalline beta-1,4-glucan, disassembly of cellulose synthase, and widespread morphological abnormalities. Microfibril crystallization may require proper assembly of the RSW1 gene product into synthase complexes whereas glucan biosynthesis per se does not.

Amino Acid Sequence↗

Olfactory basis of host location by mosquitoes and other haematophagous Diptera.

The behavioural role of odours released by mosquito hosts is poorly understood, indeed for many species it is still uncertain whether olfactory cues play a significant part in host location. Generalist attractants, such as CO2, have found application in mosquito trapping systems, and yet more host-specific attractants, such as L-lactic acid, remain of questionable value. Recent work with other haematophagous Diptera, notably Glossina, has shown that by a co-ordinated multidisciplinary approach it is possible to develop odour-baited trapping systems with a high level of attractiveness and specificity. Many of the compounds shown to attract Glossina have been tested with mosquitoes, and one of these, 1-octen-3-ol, attracts female mosquitoes of a number of species, but only in the presence of CO2. The behavioural significance of other compounds identified as host attractants of haematophagous Diptera, such as phenols, indoles and carboxylic acids, are currently under investigation. Efforts to produce a host odour attractant for the highly anthropophilic species Anopheles gambiae have been hindered by the chemical nature of the compounds associated with its human host, although a number of short-chain fatty acids identified in sweat samples have been shown to be electrophysiologically active.

Animals↗

Identification of electrophysiologically-active compounds for the malaria mosquito, Anopheles gambiae, in human sweat extracts.

Human sweat samples were chemically fractionated into acid and non-acid components. The most abundant volatile compounds present in the fractions were identified by linked gas chromatography mass spectrometry. The acid fractions were found to be composed of a range of twenty aliphatic and three aromatic carboxylic acids ranging, on average, from 0.02 to 20 micrograms per ml of sweat sampled. Non-acid fractions were found to contain: 6-methyl-5-hepten-2-one, 1-octen-3-ol, decanal, benzyl alcohol, dimethylsulphone, phenylethanol, phenol and 4-methylphenol, collectively amounting to 0.1 and 3 micrograms per ml of sweat. The major component of sweat was found to be L-lactic acid which constituted from 1 to 5 mg/ml. Using the intact antennae of the anthropophilic malaria vector mosquito Anopheles gambiae Giles, the peripheral olfactory activities of compounds identified in the sweat fractions were investigated by electroantennography (EAG). Short-chain saturated carboxylic acids, methanoic, ethanoic, propanoic, butanoic, pentanoic and hexanoic acids were found to elicit significantly larger EAG responses than longer chain saturated carboxylic acids from female An.gambiae. For a given dose the largest amplitude EAG response was elicited by methanoic acid. Pentanoic acid elicited larger EAG responses than either butanoic or hexanoic acids. Two non-acidic compounds, 1-octen-3-ol and 4-methylphenol, were found to elicit significant dose-dependent EAG responses from female An.gambiae. 1-Octen-3-ol elicited larger EAG responses than 4-methylphenol for a given dose, but both compounds elicited smaller EAG responses than the same dose of C1-C6 straight-chain aliphatic carboxylic acids. The possible behavioural significance of the EAG-active compounds identified in human sweat samples is discussed.

Adult↗

p53 gene mutations with chromosome 17 abnormalities in chronic myelogenous leukemia blast crisis patients persist in long-term cell lines but may be acquired in acute myeloid leukemia cells in vitro.

Altered p53 tumor suppressor genes have been described in various human malignancies, including in chronic myelogenous leukemias (CML) and acute myelogenous leukemias (AML), as well as their derivative cell lines. It has been proposed that this gene mutation may be less frequent in myeloid leukemia patients than in myeloid leukemia cells lines and that the latter acquire these mutations during growth in vitro. We investigated this possibility by studying p53 gene alterations in matched samples of fresh leukemic cells and their respective derivative cell lines obtained from two CML blast crisis and one AML patient. No gross structural abnormalities were detected in the p53 gene in any of the samples analyzed. Discrete mutations in the gene in the two CML blast crisis samples and in all three derivative cell lines were, however, detected by polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) analyses and DNA sequencing. Cytogenetic analyses revealed either numerical or structural, as well as numerical, abnormalities of chromosome 17 in their karyotypes. Cells from the two CML blast crisis patients had two different mutations which were maintained as the sole mutations in the cell lines. The mutation detected in the AML cell line was, however, not detectable in the parental fresh leukemic cells. Our findings demonstrate that p53 mutations and chromosome 17 abnormalities occurring in CML blast crisis patients persist in long-term cell lines but that mutations not detectable in AML patients may indeed be acquired in cell lines established from them in vitro.

Adult↗

KBM-7, a human myeloid leukemia cell line with double Philadelphia chromosomes lacking normal c-ABL and BCR transcripts.

A human myeloid leukemia cell line, KBM-7, was developed from a patient in the blastic phase of chronic myeloid leukemia (CML). We characterized its morphology, immunophenotype, cytogenetics, and proliferative capacity. Developed in the absence of exogenous lymphokines, KBM-7 in vitro cloning capacity actually decreased when colony-stimulating factors were added. The cells had an aberrant immature myeloid phenotype, a doubling time of 22 h in suspension cultures and a high cloning efficiency in semisolid system (24 +/- 3)%. Early passages contained one near-haploid (predominant) and one hyperdiploid stem line. Gradually the hyperdiploid stem line became predominant, reaching an average of 49 chromosomes per cell. Cells from passage 89 had two Philadelphia chromosomes [t(9;22)(q34;q11)] and lacked normal copies of chromosomes 9 and 22. Detailed molecular characterization of the breakpoint in the t(9;22)(q34;q11) revealed that KBM-7 had the BCR 2/ABL II splice junction. The cells had high protein kinase (p210BCR-ABL) activity and carried two identified variants of an ABL-BCR message. There was no evidence that normal BCR or c-ABL messages were expressed, assessed with the reverse-transcriptase polymerase chain reaction. When KBM-7 cells were heterotransplanted into nude mice without immunosuppressive pretreatment, one of three mice injected with 1 x 10(7) cells and all mice injected with 1 x 10(8) cells developed slowly growing granulocytic sarcomas within 6-8 weeks. These tumors were locally invasive but did not metastasize. We conclude that the KBM-7 cell line will be of value for investigating molecular events underlying neoplastic transformation in CML, in particular for studying the effects of BCR-ABL and ABL-BCR on the proliferation of CML cells in the absence of normal BCR and c-ABL messages.

Animals↗

Detection of subgroups of chronic B-cell leukemias by FMC7 monoclonal antibody.

Monoclonal antibody FMC7 detects subgroups of B-cell leukemias that have arisen from cells in late stages of B-cell maturation. FMC7 was studied by flow cytometry on cell samples from 192 patients with a diagnosis of chronic lymphocytic leukemia (CLL) or lymphoma. The leukemic cells from 16 patients were reactive with this antibody. These 16 cases were evaluated for other surface markers, morphology of cells, and clinical characteristics. Of the 16 patients, 14 had cells that strongly expressed surface immunoglobulin (SIg). This is atypical of CLL cells, which characteristically show weak expression of SIg. Eleven cases had kappa and five had lambda light chain. All patients' cells had consistently brighter CD20 expression than that of CD19. Fourteen patients had expression of CD5 on their leukemic cells. One patient had more than 55% prolymphocytes, meeting the criteria of prolymphocytic leukemia (PLL), two patients had CLL in prolymphocytic transformation (CLL/PL), and two other patients were classified as having a paraimmunoblastic variant of small lymphocytic lymphoma based on a high number of paraimmunoblasts and on the histologic features. Another nine patients had immature lymphoid cells distinct from prolymphocytes or paraimmunoblasts on morphologic study. The immature cells were variable in size, and the nuclear chromatin was less clumped than that of prolymphocytes. The histologic diagnoses in four of these cases were consistent with mantle cell lymphoma. Splenomegaly was observed in 11 patients (69%), and 11 patients had advanced Rai 3 or 4 disease. Among 10 patients treated with fludarabine, five responded to therapy. Monoclonal antibody FMC7 is useful for identifying a group of atypical variants of CLL, PLL, and other B-cell lymphomas in leukemic phase that can be easily confused with CLL. Careful attention to the cell morphology and histologic features is important for the differential diagnosis of FMC7-positive, B-cell lymphoproliferative diseases.

Adult↗

Identification of electrophysiologically-active compounds for New World screwworm, Cochliomyia hominivorax, in larval wound fluid.

Acidic and non-acidic fractions from extracts of fluid from sheep wounds infested with larvae of Cochliomyia hominivorax (Coquerel) were analysed by linked gas chromatography and electroantennography in order to detect electrophysiologically-active compounds that could be potential attractants. Responses to twenty-six electrophysiologically-active compounds were observed and, on the basis of electron impact and chemical ionization mass spectrometry and co-chromatography with authentic compounds, twenty-five of these compounds were characterized. The most abundant compounds identified in the larval wound fluid were straight and methyl-branched aliphatic carboxylic acids, ranging from C2- to C5-carbon chain length. Butanoic acid, for example, was found to be present at approximately 0.45 mg/ml. Aliphatic carboxylic acids with longer chain lengths were also observed but in trace amounts. Three aromatic carboxylic acids, benzoic, phenylethanoic and 3-phenylpropanoic acids were also present but only phenylethanoic and 3-phenylpropanoic acids elicited electroantennographic responses. Phenol and indole were by far the most abundant components of the non-acid fraction of the larval wound fluid with all other components, except delta-valerolactam, present at levels of less than 5% that of phenol which was present at a concentration of 0.05 mg/ml. Electroantennographic studies of straight-chain aliphatic carboxylic acids showed that pentanoic acid elicited the strongest response from C. hominivorax. Similar studies showed that 1-octen-3-ol elicited stronger responses than 3-methylphenol, indole, phenol or dimethyldisulphide. 3-Methylindole, which was not found in the wound fluid, also elicited a strong response. The potential behavioural significance of these compounds is discussed in relation to that of known attractants of C. hominivorax and other dipteran pests of mammals.

Alcohols↗