Feeding responses to solanaceous allelochemicals by larvae of the tobacco hornworm, Manduca sexta

Feeding responses of the oligophagous tobacco hornworm to allelochemicals prevalent in their host plants were determined in food choice-tests using filter paper discs laced with a test solution or water (control). Six solanaceous alkaloids, tomatine, tomatidine, solanine, solanocapsine, atropine and nicotine, were tested and only tomatine and solanocapsine were found to influence preference behavior. Solanocapsine (5 mM) deters feeding whereas tomatine (1 mM) stimulates feeding slightly. No synergistic effect of either tomatine or tomatidine with sucrose was found.The responses to tomatine are affected by previous feeding experience. Tomatine slightly stimulates feeding in larvae reared on tomato (Lycopersicon esculentum), but slightly deters feeding in larvae reared on Jerusalem cherry (Solanum pseudocapsicum). Such induced preference is absent for the other alkaloids tested, which indicates that these alkaloids do not by themselves induce preferences for the plants containing them.The non-alkaloid allelochemicals, chlorogenic acid, rutin, and 2-tridecanone also influenced food choice behavior. Chlorogenic acid is slightly stimulatory at its natural concentration (1mM), but strongly deterrent at higher concentrations. Rutin stimulates feeding in a concentration-dependent manner. Its activity must be due to the glycosylated structure, because both the aglycone (quercetin) and the sugar moiety (rutinose) are neutral. Removal of the glucose part of rutin, as in quercitrin, results in feeding deterrent activity. 2-Tridecanone is neutral at its concentration in cultivated tomato (1 mM), but strongly deterrent and toxic at higher concentrations. Preference behavior is not affected by solanesol, GABA, and a mixture of host plant compounds stimulatory for anothe solanaceous-specific feeder, the Colorado potato beetle (Leptinotarsa decemlineata).We conclude that the prevalent solanaceous alkaloids and other allelochemicals tested do not play important roles in food selection of the tobacco hornworm, although some may make small contributions.

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Résumé Des experiences de choix de chenilles oligophages de M. sexta ont été réalisees avec des disques de papier filtre imbiles d'eau ou de solutions des substances allélochimiques dominantes dans les plantes consommées. Sur les six alcaloïdes de solanées examinés: tomatine, tomatidine, solanine, solanocapsine, atropine et nicotine, seuls la tomatine et la solanocapsine ont influé sur le choix; la solanocapsine (5 mM) empêche la prise de nourriture, tandis que la tomatine (1 mM) la stimule légèrement. Aucun effet synergique de la tomatine ou de la tomatidine n'a été observé en présence de sucrose.La réponse à la tomatine est modifiée par la prise de nourriture antérieure. Elle stimule légèrement l'alimentation de chenilles élevées sur tomates (Lycopersicon esculentum), mais dissuade légèrement les chenilles élevées sur Solanum pseudocapsicum. II n'y a pas d'action induite semblable avec les autres alcalïdes examinés, ce qui indique que ces alcaloïdes ne peuvent pas induire par eux-mêmes de préférences pour les plantes qui les contiennent.Des substances allélochimiques non-alcaloïdes: acide chlorogénique, rutine, et 2-tridécanone, influent aussi sur le comportement de choix alimentaire. L'acide chlorogénique est légèrement stimulant à sa concentration naturelle (1 mM), mais fortement dissuasif aux concentrations supérieures. La rutine stimule la prise de nourriture en fonction de sa concentration. Son activité doit être due à sa structure glucosylate, puisqu'aussi bien l'aglycone (quercitine) que la moiteé sucrée (rutinose) sont neutres. La suppression de la partie glucose de la rutine, comme dans le cas de la quercitine, a un effet dissuasif. A sa concentration dans la tomate cultivée (1 mM), le 2-tridécanone est neutre, mais il est fortement dissuasif et toxique à des concentrations supérieures.Le comportement de choix n'est pas modifié par le solanésol, le GABA, et par un mélange de composés végétaux stimulant un consommateur spécifique de solanées, comme le doryphore (Leptinotarsa decemlineata).Nous pouvons conclure que les principaux alcaloïdes et autres substances allélochimiques des solanées que nous avons examinés n'interviennent pas d'une façon importante, mais peuvent avoir une influence secondaire, dans les choix alimentaires de Manduca sexta.

     

Effect of disinfection of drinking water with ozone or chlorine dioxide on survival of Cryptosporidium parvum oocysts.

Demineralized water was seeded with controlled numbers of oocysts of Cryptosporidium parvum purified from fresh calf feces and subjected to different treatments with ozone or chlorine dioxide. The disinfectants were neutralized by sodium thiosulfate, and neonatal mice were inoculated intragastrically and sacrificed 7 days later for enumeration of oocyst production. Preliminary trials indicated that a minimum infection level of 1,000 oocysts (0.1-ml inoculum) per mouse was necessary to induce 100% infection. Treatment of water containing 10(4) oocysts per ml with 1.11 mg of ozone per liter (concentration at time zero [C0]) for 6 min totally eliminated the infectivity of the oocysts for neonatal mice. A level of 2.27 mg of ozone per liter (C0) was necessary to inactivate water containing 5 x 10(5) oocysts per ml within 8 min. Also, 0.4 mg of chlorine dioxide per liter (C0) significantly reduced infectivity within 15 min of contact, although some oocysts remained viable.     

Cloning and sequencing of the gene encoding flavodoxin from Desulfovibrio vulgaris Hildenborough

Abstract The gene encoding flavodoxin from Desulfovibrio vulgaris Hildenborough (148 amino acid residues), the first flavoprotein for which a three-dimensional structure has been determined, was cloned with the use of two synthetic oligonucleotides, designed to recognize the coding sequence for amino acid residues 11–19 and 98–103, respectively. The two oligonucleotides were used to screen a library of 900 λ-clones of the D. vulgaris chromosome. A single clone, λFL1, reacting with both probes was isolated. The entire structural gene for flavodoxin is contained in the 15 kb insert of λFL1 as found by nucleic acid sequencing. The codon usage in the flavodoxin gene is strongly biased towards G or C in the third codon position. A table in which codon usage information from all genes of D. vulgaris sequenced to date is combined is presented and should facilitate further gene cloning with oligonucleotide probes.     

Kinetics of nitrite oxidation in two Nitrobacter species grown in nitrite-limited chemostats

The influence of growth rate, the presence of acetate and variation in the dissolved oxygen concentration on the kinetics of nitrite oxidation was studied in suspensions of intact cells of Nitrobacter winogradskyi and Nitrobacter hamburgensis. The cells were grown in nitrite-limited chemostats at different dilution rates under chemolithotrophic and mixotrophic conditions. Growth of N. hamburgensis in continuous culture was dependent on the presence of acetate. Acetate hardly affected the maximal nitrite oxidation rate per cell (V _max), but displayed a distinctly negative effect on the saturation constants for nitrite oxidation (K _m ) of both Nitrobacter species. This effect was reversible; when acetate was removed from the suspensions the K _m -values for nitrite oxidation returned to their original values. A reduction of the dissolved oxygen concentration from 100% to 18% air saturation slightly decreased the V _max of chemolithotrophically grown N. winogradskyi cells, whereas a 2.3 fold increase was observed with mixotrophically grown cells of N. hamburgensis. It is suggested that the large variation in K _m encountered in field samples could be due to this observed phenotypic variability. The V _max per cell is not a constant, but apparently is dependent on growth rate and environmental conditions. This implies that potential nitrite oxidation activity and numbers of cells are not necessarily related. Considering their kinetic characteristics, it is unlikely that N. hamburgensis is able to compete succesfully with N. winogradskyi for limiting amounts of nitrite under mixotrophic conditions. However, at reduced partial oxygen tensions, N. hamburgensis may become the better competitor.     

Thyroid function and trisomy 21. TSH increase and rT3 deficiency

An excess of thyrotropin (TSH) with normal levels of tetraiodothyronine (T4) and of 3,5,3'-triiodothyronine (T3) was confirmed in the serum of 78 trisomy 21 children. A severe deficiency of 3,3',5'-triiodo-thyronine (rT3 or reverse T3) was observed and the decrease of the rT3/TSH ratio was highly significant. These new facts suggest that the rT3 deficiency plays a peculiar role in trisomy 21 (maybe through the regulation of one or few steps of monocarbons' metabolism). A systematic control of thyroid function (including the patient's rT3 level) is mandatory for the follow-up of every trisomy 21 patient.     

A new lectin from tulip (Tulipa) bulbs

A lectin was isolated from tulip (Tulipa) bulbs by affinity chromatography on fetuin-agarose and partially characterized. The tulip lectin is a tetrameric protein composed of four identical subunits of M_r 28 000, which are not held together by disulphide bonds. It is not glycosylated and has an amino-acid composition typified by a high content of asparagine-aspartic acid, leucine, glycine and serine. Tulip lectin agglutinates human red blood cells, but has a much higher specific activity with rabbit erythrocytes. In hapten-inhibition assays with the latter type of red blood cell the lectin exhibits a complex specificity, whereas its agglutination with human erythrocytes is readily inhibited by N-acetylgalactosamine, lactose, fucose and galactose.Abbreviations DEAE diethylaminoethyl - PBS phosphate-buffered saline - TL Tulipa lectin - M_r relative molecular mass - SDS-PAGE sodium dodecyl sulphate-polyacrylamide gel electrophoresis     

Influence of vasoconstriction, temperature, and flow on the kinetics of serotonin uptake in rabbit lungs

In the process of estimating the kinetic parameters of the pulmonary endothelial serotonin (5-HT) uptake, it is critically important to distinguish the effects of hemodynamic changes from endothelial injury. Therefore, the effects of changes in flow rate (1.7-5.0 ml/s), hemodynamics (vasoconstriction by norepinephrine), and temperature (39 vs. 33 degrees C) were investigated in isolated rabbit lungs. Indicator-dilution data were expressed in terms of the Michaelis-Menten equation for the two 5-HT uptake pathways in the preparation. The maximum uptake velocity (Vmax1) and the 5-HT concentration at half-maximum velocity (Km1) of the first pathway as well as the first-order constant (Vmax2/Km2) of the linear part of the second pathway were determined. Neither vasoconstriction nor flow variations had any effect on Km1, whereas increasing the flow rate caused extensive recruitment, with a concomitant increase in Vmax1 and Vmax2/Km2. Furthermore, all the kinetic parameters were significantly decreased at the lower temperature. We conclude that Km1 is independent of organ hemodynamics (vasoconstriction and flow) but susceptible to changes in 5-HT uptake capacity caused by a change in temperature. Vmax1 and Vmax2/Km2 respond to alterations in 5-HT uptake capacity and perfused organ volume. These are prerequisites to apply kinetic modeling as a method for the investigation of pulmonary endothelial function and integrity.     

Relationship between the thyroidal and gonadal axes during the estrous cycle of ewes of different breeds and ages

In order to define the patterns of TSH, T4, T3, rT3, GH and cortisol during the estrous cycle of sheep, pluriparous and primiparous ewes were synchronized with progestagen-impregnated pessaries (Veramix) at the start of the normal breeding season. After the pessaries were removed (day 0), daily blood sampling was carried out in cannulated ewes during the ovulatory cycle. Hormonal analyses of TSH, T4, T3, rT3, GH, cortisol, LH and progesterone (P) were performed by RIA. P and LH levels during the cycle were conform to the literature and were not different between the primiparous and pluriparous ewes of different breeds used in this study. Neither age nor breed influenced the hormone patterns. A significant negative correlation was found between TSH and P during the cycle, although the correlation between P and T4 was not significant; during the estrous period, low P levels were paralleled by high T4 levels, whereas the reverse was observed during the luteal phase. Higher T3 levels and T3/T4 ratios were observed during the luteal phase. No obvious pattern of rT3 and cortisol during the cycle was found. The GH concentration increased during the 17 days of the cycle. A positive correlation with P was calculated. During the estrous cycle obvious changes in thyroid hormones, GH and TSH occurred. However, this study shows no causal relationship between the thyroid and the gonadal axes.