Activation of hibernating Coccinella septempunctata (Coleoptera) and Perilitus coccinellae (Hymenoptera) and the photoperiodic response after diapause

To measure the progress of diapause termination in December and March and the difference in diapause intensity between populations from two altitudes, Coccinella septempunctata adults were exposed to 25° and to photoperiods 18L:6D or 12L:12D and the oviposition was recorded.In early December, C. septempunctata females from 600 m had the pre-oviposition period 1/3–2/3 shorter than the population from 1500 m. It was shorter under long day and in injured coccinellids under short day than in intact insects under short day. In mid-March the pre-oviposition period was considerably shorter, both after the hibernation outdoors and under 15°, indicating thus that diapause was over in almost all females. Photoperiodic response in post-diapause insects was shown by a gradual halt of oviposition after a decrease in daylength.In contrast to pre-oviposition of C. septempunctata, the pre-pupal period of Perilitus coccinellae did not get shorter between December and March.

---

Résumé En vue d'apprécier l'intensité de la diapause et son état d'avancement au cours du temps, en fonction des conditions d'hivernage, deux populations de Coccinella septempunctata sont récoltées dans le sud-ouest de la France, l'une à 600 m d'altitude, l'autre à 1512 m. Les insectes sont prélevés, d'une part, au milieu de la période d'hivernation (2 décembre), d'autre part, en fin de cette période (20 mars). Ils sont soumis à des photopériodes longues (18 L:6D) ou courtes (12 L:12D), dans des conditions de température de 25°, et on compare le délai nécessaire pour obtenir la ponte (période de pré-oviposition). Certains lots ont subi une mutilation, à titre expérimental: section des ailes postérieures.Chez les insectes prélevés début décembre, la durée de la période de pré-oviposition est de 1/3 à 2/3 plus courte pour la population de plaine hivernant à 600 m d'altitude. L'activation est plus rapide en jours longs (18h de photophase); elle est aussi plus rapide chez les coccinelles mutilées que chez des femelles indemnes, lorsqu'elles sont placées en jours courts.Chez les insectes prélevés en mi-mars la période de pré-oviposition est beaucoup plus courte; il en est de même chez des insectes prélevés en décembre mais maintenu en hibernation artificielle au laboratoire à une température de 15° et à l'obscurité. Des femelles réactivées en jours longs se révèlent sensibles dès l'achèvement de la diapause à une réduction de la photopériode qui provoque un arrêt progressif de la ponte.En contraste avec les variations observées dans la durée de la période de pré-oviposition chez les coccinelles réactivées en décembre ou en mars, la période de pré-émergence de leur parasite Perilitus reste la même et n'est pas plus courte en mars qu'en décembre.

---

---

Dedicated to Prof. Dr. Jan de Wilde, Wageningen, on the occasion of his 60th birthday.     

Flight potential and oxygen uptake during early dormancy in Coccinella septempunctata

Two flight parameters (take-off and duration) and respiration level were measured, in two years in summer and early autumn, in dormant Coccinella septempunctata L. (Coleoptera: Coccinellidae) collected while hidden in grass tussocks in hibernation sites (HID) and in beetles collected on plants (PLA). The duration of tethered flight of HID beetles measured in the laboratory in late August and September 1995 (range of geometric means 190–440 s) was slightly longer than the flight of PLA beetles (80–310 s), both being much longer than trivial flight recorded in beetles foraging for prey during the breeding season (35 s). In general, the flight performance had a tendency to increase in September and to decrease in October.The oxygen consumption in HID beetles increased throughout September 1994 from 430 to 780 l g^–1 h^–1 and throughout October 1995 from 710 to 1060 l g^–1 h^–1. This increase is ascribed to a concomitant decrease in diapause intensity. A similar increase was observed also in PLA beetles in 1994 and oxygen consumption was always higher than in HID beetles, most probably due to feeding and digestion in PLA beetles.Laboratory feeding of HID beetles on aphids induced maturation of ovaries and increased oxygen uptake (from 680 to 1110 l g^–1 h^–1). Feeding on honey and pollen left their oxygen uptake unchanged. Effect of feeding on the flight parameters was mostly not significant. In agreement with its less suitable body shape and usually less distant dormancy sites, C. septempunctata was found a less apt flier than long-distance migrating coccinellid species.     

Effect of thermoperiod on diapause intensity in Pyrrhocoris apterus (Heteroptera Pyrrhocoridae)

The intensity of adult diapause in Pyrrhocoris apterus was measured in two series of experiments as the duration of pre-oviposition period at a constant temperature of 25 degrees C after transfer from short (12L:12D) to long day conditions (18L:6D). Higher diapause intensity was induced with a thermoperiod than at constant temperatures. After the induction throughout larval instars 3-5 and during 4 weeks of adult life at short days and a thermoperiod of 25/15 degrees C the pre-oviposition period was 30+/-4 and 26+/-3 days. After induction at constant 25 degrees C the pre-oviposition period was 22+/-3 and 23+/-4 days, while after induction at constant 20 degrees C it was 17+/-4 and 19+/-4 days. Induction at a lower constant temperature of 20 degrees C was thus followed by a less intense diapause than the induction at a higher constant temperature of 25 degrees C. These counterintuitive results are discussed. The oxygen consumption rate measured at experimental temperatures prior to transfer from short to long days was higher at thermoperiodic conditions than at constant temperatures and it was similar at constant 20 and 25 degrees C. Thus, the oxygen consumption rate measured prior to the transfer was highest (indication of the least intense diapause) in the insects that showed later, after the transfer to long days, the longest pre-oviposition period (indication of the most intense diapause). Within the first two days after transfer to constant 25 degrees C, oxygen consumption rate measured at 25 degrees C decreased in the thermoperiodic insects, while it transiently increased in insects from constant 20 degrees C. Two days and later after the transfer, oxygen consumption rate was similar in all groups. Cold hardiness was not correlated with diapause intensity. The low lethal temperature in diapausing insects was correlated with the night temperature during diapause induction.     

Non-closure of peritoneum after abdominal hysterectomy for uterine carcinoma does not increase late intestinal radiation morbidity

Background/AimTo evaluate whether non-closure of the visceral peritoneum after total abdominal hysterectomy (TAH) and bilateral salpingo-oophorectomy (BSO) in patients with uterine corpus carcinoma influences the volume of the small intestine within the irradiated volume during adjuvant radiotherapy or late radiation intestinal toxicity.Materials and methodsA total of 152 patients after TAH + BSO with adjuvant pelvic radiotherapy were studied. The state of peritonealization was retrospectively evaluated based on surgical protocols. The volume of irradiated bowels was calculated by CT-based delineation in a radiotherapy planning system. The influence of visceral peritonealization upon the volume of the small intestine within the irradiated volume and consequent late morbidity was analyzed.ResultsVisceral peritonealization was not performed in 70 (46%) of 152 studied patients. The state of peritonealization did not affect the volume of the irradiated small intestine (p = 0.14). Mean volume of bowels irradiated in patients with peritonealization was 488 cm³ (range 200–840 cm³, median 469 cm³); mean volume of bowels irradiated in patients without peritonealization was 456 cm³ (range 254–869 cm³, median 428 cm³). We did not prove any significant difference between both arms. Nor did we observe any influence of non-peritonealization upon late intestinal morbidity (p = 0.34).ConclusionNon-closure of the visceral peritoneum after hysterectomy for uterine corpus carcinoma does not increase the volume of the small intestine within the irradiated volume, with no consequent intestinal morbidity enhancement.     

alpha-Naphthoflavone acts as activator and reversible or irreversible inhibitor of rabbit microsomal CYP3A6.

This report describes the effect of alpha-naphthoflavone (alpha-NF), a known substrate, inhibitor and activator of several cytochromes P450 (CYP), on rabbit CYP3A6. Hepatic microsomes of rabbit pretreated with rifampicine (RIF), enriched with CYP3A6, as well as purified CYP3A6 reconstituted with isolated NADPH:CYP reductase were used as enzymatic systems in this study. The data from difference spectroscopy experiments showed that alpha-NF does yield a type I binding spectrum. This compound is oxidized by microsomal CYP3A6 into two metabolites (5,6-epoxide and trans-7,8-dihydrodiol). While alpha-NF is a substrate of CYP3A6, it also acts as an enzyme modulator. Under the conditions used, stimulation of 17beta-estradiol 2-hydroxylation by alpha-NF was observed. In contrast, this compound reversibly inhibited N-demethylation of erythromycin and tamoxifen, competitively with respect to these substrates, having the K(i) values of 51.5 and 18.0 microM, respectively. Moreover, alpha-NF was found to be an effective inactivator of progesterone and testosterone 6beta-hydroxylation catalyzed by CYP3A6 in RIF-microsomes. In addition, time- and concentration-dependent inactivation of human CYP3A4-mediated 6beta-hydroxylation of testosterone by alpha-NF, was determined. The inactivation of CYP3A6 followed pseudo-first-order kinetics and was dependent on both NADPH and alpha-NF. The concentrations required for half-maximal inactivation (K(i)) were 80.1 and 108.5 microM and the times required for half of the enzyme to be inactivated were 10.0 and 11.9 min for 6beta-hydroxylation of progesterone and testosterone, respectively. The loss of the enzyme activity was not recovered following dialysis, while 90% of the ability to form a reduced CO complex remained. This indicates the binding of alpha-NF to a CYP apoprotein molecule rather than to a heme moiety. Protection from inactivation was seen in the presence of all tested CYP3A substrates. Progesterone and testosterone protected CYP3A6 against inactivation competitively with respect to inactivator, erythromycin non-competitively and 17beta-estradiol showed a mixed type of protection. Here, we described for the first time that alpha-NF is capable of irreversible inhibition of microsomal rabbit CYP3A6 and human CYP3A4. The obtained results strongly suggest that the CYP3A active center contains at least two and probably three distinct binding sites for substrates.     

Habitat and food specificity in aphidophagous predators

Current knowledge of the processes underlying prey location and choice by aphidophagous predators is reviewed by considering the succession of behavioural mechanisms required for the predator to obtain prey. The predator may locate areas where prey are likely to be found by responding to physical aspects of the habitat, or to semiochemicals produced by the host plant. The predator may then respond to visual or olfactory cues to locate the aphid prey. The predator's readiness to attack and consume aphids is influenced by any behavioural or chemical defence strategies, and by the palatability or nutrient value of the aphids. Toxic allelochemicals ingested by aphids from their host plant may have a detrimental effect on predators.     

Termination of adult diapause in Pyrrhocoris apterus (Heteroptera: Pyrrhocoridae) in the field

The time when diapause ends in the Czech population of Pyrrhocoris apterus was studied by the transfer of the overwintering bugs to laboratory conditions of 25°C and long day (L 18, D 6) or short day (L 12, D 12).Both the incidence of oviposition after the transfer to short-day conditions and the duration of the pre-oviposition period after the transfer to long-day conditions indicate that the diapause ends in the period of December–January. Development is then inhibited environmentally, by low temperatures.Thus the diapause of P. apterus is terminated before the advent of hard frosts. The resistance to frost is not bound to the condition of the intrinsic inhibition of the maturation of gonads.

---

Zusammenfassung Die Termination der Diapause kann nicht — wie vielfach angenommen wird — mit der Wiederaufnahme der Entwicklung gleichgesetzt werden, da in der Natur die Entwicklung nach dem Ende der Diapause meist durch niedrige Temperaturen noch weiterhin inhibiert bleibt (Quieszenz). Um das wahre Ende der Diapause bei Pyrrhocoris apterus zu ermitteln, wurden Wanzen im Verlaufe der Überwinterung (Hiberntion) (August–März) in abgestuften Intervallen aus dem Freien ins Laboratorium übertragen, wo 25° und 24-stündige Photoperioden mit Photophasen von 12 oder 18 std herrschten.Die Versuche wurden während drei Winterperioden durchgeführt (1964–65, 1966–67, 1967–68) und dabei Wanzen aus drei klimatisch unterschiedlichen Lokalitäten: Smolenice, Slaný und Jankovice (Seehöhe 240, 280 bzw. 430 m) verglichen, deren mittlere Jahres-temperatur 9,0, 8,2 bzw. 7.5° beträgt. Die Wanzen wurden paarweise bei Lindensamen und Wasser gehalten. In allen Versuchen wurde Eiablage, bei manchen auch Kopulation, Eianzahl und Schlüpfrate, täglich ermittelt.Im Langtag (L 18, D 6) begannen die Weibchen stets Eier zu legen, doch verkürzte sich im Verlaufe der Überwinterung schrittweise die Länge der Präovipositionsperiode. Zwischen August und Anfang Oktober begannen die Eiablagen in der Regel nach 26–34 Tagen. Nach Mitte Januar (manchmal auch schon ab Dezember) verkúrzte sich die Präovipositionsperiode auf nur 8–9 Tage, was dem Wert der Präovipositionszeit bei Nondiapause-Tieren entspricht.Im Kurztag (L 12, D 12) blieben die diapausierenden Wanzen unfruchtbar. Die Weibchen der August- und September-Proben legten überhaupt keine Eier (obwohl sie zwei über drei Monate lang gehalten wurden. Die Weibchen der im Oktober und November eingeholten Proben legten nur zu einem geringen Prozentsatz (14 bzw. 32%) und nach längerer Präovipositionsperiode ab. Bereits ab Mitte Dezember legten jedoch alle Weibchen nach einer Präovipositionsperiode von nur 8–11 Tagen ab.In der Natur endet also die imaginale Diapause bei tschechischen Populationen von P. apterus schon im Dezember, gegebenenfalls im Januar, d.h. noch vor Eintritt strengerer Fröste. Der Adaptationswert der Diapause beruht daher nicht auf einer direkten Erhöhung der Frostresistenz, sondern auf der Synchronisation des Lebenszyklus der Insekten mit der Jahreszeit.Die photoperiodische Termination der imaginalen Diapause bei P. apterus wird mit ähn-lichen Erscheinungen bei anderen Insektenarten verglichen.

     

Heterobifunctional photoaffinity probes for cytochrome P450 2B.

Three heterobifunctional photoaffinity probes, N-(p-azidobenzyl)-N-methyl-p-aminobenzylamine (I), N-(p-azidobenzyl)-N-methyl-p-aminophenethylamine (II), and N-(p-azidophenethyl)-N-methyl-p-aminophenethylamine (III), were synthesized and characterized. These probes, containing a photolabile azido-group and an amino-group on opposite sides of the molecule, were designed for photoaffinty labeling of the cytochrome P450 (CYP) 2B active site cavity differing in distance from the heme iron. Spectroscopic studies proved that probes I and II coordinated with the heme iron via their amino-group in the enzyme active center, whereas probe III did not. This result in conjunction with data from kinetic studies suggests probes I and II are appropriate for photoaffinity labeling of the CYP 2B active center. Thus, probe II was used to identify amino acid residues within a distance of the probe length (about 16.5 A) from the heme. Analysis of a Lys-C digest of the probe II-labeled CYP 2B4 revealed a single labeled hexapeptide corresponding to position 192-197 of the CYP 2B4 sequence. Using postsource decay/matrix-assisted laser desorption ionization-time of flight, Arg197 was identified as a probe II target. The location of the labeled site in three-dimensional structures of bacterial CYPs and in CYP 2B homology models is discussed.