Journal of Insect Physiology 54 (2008) 17–24
Eicosanoids mediate melanotic nodulation reactions to viral infection in
larvae of the parasitic wasp, Pimpla turionellae
Yonca Durmus-a, Ender Bu¨yu¨kgu¨zela, Burcin Terzia, Hasan Tunazb,
David Stanleyc,Ã, Kemal Bu¨yu¨kgu¨zela
aDepartment of Biology, Faculty of Arts and Science, Karaelmas University, Zonguldak, Turkey
bDepartment of Plant Protection, Faculty of Agriculture, Kahramanmaras- Su¨tc-u¨ I˙mam University, Kahramanmaras-, Turkey
cUSDA/Agricultural Research Service, Biological Control of Insects Research Laboratory, 1503 S. Providence Rd., Columbia, MO 65203, USA
Received 1 February 2007; received in revised form 21 March 2007; accepted 21 March 2007
Nodulation is the quantitatively predominant insect cellular immune function activated in response to bacterial, fungal and some viral
infections. We posed the hypothesis that parasitoid insects express melanotic nodulation reactions to viral challenge and that eicosanoidsmediate these reactions. Treating fifth-instar larvae of the ichneumonid endoparasitoid Pimpla turionellae with Bovine Herpes SimplexVirus-1 (BHSV-1) induced nodulation reactions in a challenge dose-dependent manner. Experimental larvae treated with thecyclooxygenase inhibitor, indomethacin, the lipoxygenase inhibitor, esculetin, and the phospholipase A2 inhibitor, dexamethasone,resulted in severely impaired nodulation reactions to our standard BHSV-1 challenge dose. The immunoinhibitory influence ofdexamethasone was reversed in larvae reared on culture medium amended with arachidonic acid, the fatty acid precursor of eicosanoidbiosynthesis. Larvae that had been reared on media amended with indomethacin, esculetin, or dexamethasone were also compromised intheir nodulation reactions to viral challenge. The influence of the orally administered pharmaceutical was expressed in a dose-dependentmanner. Finally, wasp larvae reared in the presence of indomethacin and dexamethasone expressed significantly decreased levels ofphenoloxidase activity in response to viral challenge. These findings draw attention to the idea that endoparasitoid insects express cellularimmune reactions to viral challenge; they also support our hypothesis that eicosanoids mediate nodulation reactions to viral challenge inthese highly specialized insects. r 2007 Elsevier Ltd. All rights reserved.
Keywords: Parasitoid wasp; Pımpla turıonellae; Cellular immunity; Nodulation; Phenoloxidase; Eicosanoids
biological actions, eicosanoids act in several aspects ofinsect immunity. Two categories of insect innate immune
Eicosanoids are produced by enzymatic oxygenation of
reactions are appreciated. Humoral reactions involve
arachidonic acid (AA) and two other C20 polyunsaturated
induced biosynthesis of various anti-microbial peptides
fatty acids. The two major groups of eicosanoids are
prostaglandins and the many lipoxygenase products.
nodulation, encapsulation and phagocytosis (
Virtually all animals are thought to biosynthesize a wide
range of eicosanoids, which serve in a large (but unknown)
number of molecular, physiological and ecological actions
bacterial infection are mediated by eicosanoids. This
eicosanoid hypothesis has been supported by reports, onover 20 insect species, from several laboratories (
). Looking in more detail than nodulation,
Corresponding author. Tel.: +1 875 573 5361x245;
eicosanoids also mediate particular steps that lead to
0022-1910/$ - see front matter r 2007 Elsevier Ltd. All rights reserved.
Y. Durmus- et al. / Journal of Insect Physiology 54 (2008) 17–24
cell spreading, a distinct phase of nodulation, and
phagocytosis are mediated by eicosanoids in larval waxmoths, Galleria mellonella. found that
The cyclooxygenase (COX) inhibitor, indomethacin
eicosanoids mediate hemocyte elongation in hemocytes
(1-(p-chlorobenzoyl)-5-methoxy-2-methyl-3-indolyl-acetic acid),
isolated from tobacco hornworms, Manduca sexta. Eico-
the 5- and 12-lipoxygenase (LOX) inhibitor esculetin (6,7-
sanoids also mediate microaggregation reactions (another
dihydroxycoumarin), the PLA2 inhibitor dexamethasone
step in nodulation) to bacterial challenge (
[(11b,16a)-9-fluoro-11-17,21-trihydroxy-16-methylpregna-
1,4-diene-3,20-dione], arachidonic acid (AA), dopamine,
bovine serum albumin (BSA), and Folin-Ciolcalteu Re-
reported that eicosanoids mediate behavioral fever re-
agent were purchased from Sigma-Aldrich (St. Louis, MO,
sponses to infection in the locust Schistocerca gregaria. The
eicosanoids also act in insect humoral immunity. found that biosynthesis of antibacterial
proteins also depends on eicosanoids in the silkworm,Bombyx mori. And reported a
Before injection, larvae were anesthetized by chilling
functional coupling between the immune deficiency path-
them on ice for 5 min and surface-sterilized by swabbing
way and eicosanoid biosynthesis in Drosophila. We surmise
their cuticles with 95% ethanol (EtOH). Injections were
eicosanoids are crucial elements in the mediation of in
carried out with a 10 ml Hamilton micro-syringe (Hamilton,
Reno, NV). Injections were performed dorso-laterally in
With respect to the nature of infecting organisms,
the abdominal segments with the pharmaceutical treat-
eicosanoids act in insect defense reactions to several species
ments and BHSV-1 challenge doses on opposite sides. The
of bacteria, two fungal species and eggs of a parasitoid
abdomen was palpated gently after injection to mix the
contents of the hemocoel. Eicosanoid biosynthesis inhibi-
tors (EBIs), indomethacin, esculetin and dexamethasone
mediate melanotic nodulation reactions to Bovine Herpes
Simplex Virus-1 (BHSV-1) challenge in larvae of the
Control insects were injected with 70% EtOH (5 ml) and
greater wax moth, G. mellonella. At a higher level of
experimental wasps with EBIs (5 mg/5 ml EtOH). All larvae
biological organization, parasitoid insects can become
were immediately challenged with BHSV-1 in a standard
exposed to viral infection via interactions with their hosts.
dosage of 2 Â 104 PFU in 5 ml of culture medium, except in
We posed the hypothesis that parasitoids also express
dose–response experiments, following the injection proto-
melanotic nodulation reactions to viral challenge and that
eicosanoids mediate these reactions. In this paper, we
at selected times after injections. The larvae were anesthe-
report on experiments with the ichneumonid endoparasi-
tized by chilling them on ice, then their hemocoels were
toid Pimpla turionellae designed to test our hypothesis.
exposed to count melanized, brownish-black nodules undera stereomicroscope at 45 Â . After initial counting, thealimentary canals were removed and nodules in theremaining internal tissues were then counted. The nodules
were distinct and direct counting reliably reflected theextent of the nodulation response to infections
A colony of P. turionellae was maintained in the
laboratory at 2371 1C, 7575% RH, and a photoperiodof 16-h light:8-h dark. Wasp larvae were reared on the
Several control experiments were conducted to deter-
pupae of the greater wax moth, G. mellonella. Adults were
mine the level of background nodulation in the wasp
fed daily with a 50% filtered honey solution and G.
larvae. Because the larvae were reared in non-sterile
mellonella pupal hemolymph every other day. Adult wasps
conditions, control experiments (no treatment) were
were allowed to oviposit in wax moth pupae. Fifth-instar
performed to register the background number of nodules
P. turionellae (20–30 mg) larvae were used in the nodula-
in the larvae. Nodulation in unchallenged larvae was
tion reaction and PO activity experiments.
assessed by randomly taking 10 fifth-instar larvae from
Stock BHSV-1 was kindly donated by Dr. Aykut O¨zkul
artificial diet, chilling them on ice, and counting the
(Veterinary Faculty, Ankara University). The virus stock
nodules, as described above. The effect of wounding on
was kept at À70 1C until used. The concentrations of virus
nodulation was determined by wounding 10 larvae with the
solutions (4 Â 106, 4 Â 105, 4 Â 104 plaque-forming units
needle of the micro-syringe. Nodulation was assessed 1 h
(PFU)/ml) were prepared by serially diluting the original
post-injection (PI). The effect on nodulation of the COX
liquid suspension with distilled water. Dilutions of the
inhibitor indomethacin, the LOX inhibitor esculetin, and
stock solution were made immediately before injection.
the phospholipase A2 inhibitor dexamethasone, BHSV-1
Y. Durmus- et al. / Journal of Insect Physiology 54 (2008) 17–24
and their solvents ethanol and distilled water, respectively,
was tested in unchallenged larvae in the same concentra-
Composition of chemically defined diet for rearing P. turionellae larvae
tion (5 mg/larva for indomethacin and 2 Â 104 PFU/larva
for virus) and volume (5 ml/larva for both solvent) as used
for challenge larvae. Nodulation was assessed at 1 h PI.
2.5. Time-course of nodulation: influence of BHSV-1
Five groups of larvae (n ¼ 10) were chilled on ice and
injected with 5 ml BHSV-1 (2 Â 104 PFU/larva) as de-
scribed. The number of nodules was counted at 1, 2, 4, 6,
For the dose–response curve, four groups of larvae
¼ 10) were chilled on ice and injected with 5 ml BHSV-1
2 Â 104 PFU per larva. Control larvae were injected with
distilled water. Nodulation was assessed at 1 h PI as
Eight groups of larvae (n ¼ 10) were tested. Individuals
in the first group were injected with 5 ml ethanol (70%) as
control. The second group was injected with 5 ml BHSV-1
(2 Â 104 PFU/larva). Groups 3–5 were injected with in-
domethacin, esculetin, or dexamethasone (5 mg/larvae).
Groups 6–8 received similar EBI treatments, and were
tion was assessed at 1 h PI as described above.
2.8. Oral treatments with EBIs and BHSV-1
Experimental wasp larvae were used for per os experi-
ments to determine nodulation reaction and PO activity.
The synthetic diet described by was used for
rearing first instar wasp larvae. The diet consisted of anamino acid mixture, a lipid mixture, an inorganic saltmixture, glucose, RNA and a mixture of water-soluble
water to achieve the final concentrations of 0.001, 0.01 and
vitamins The methods used in the preparation of
the diets and dispensing these diets into test-tubes,
To obtain wasp larvae, wax moth pupae were para-
obtaining the eggs and first instar larvae and their
sitized. The wasp eggs were recovered by dissecting the
inoculation onto diets were described elsewhere
parasitized hosts in saline solution (0.8% solution of
NaCl). The larvae were allowed to hatch in the saline
prepared in two parts. A vitamin–glucose mixture was
prepared first. The remaining diet components were
All the feeding experiments were started by inoculating
prepared and autoclaved for 15 min at 121 1C for dissolving
the newly hatched larvae into 10 mm  75 mm tubes
the agar. Finally, the parts were combined in a sterile glove
charged with 0.5 ml diet. Each tube received one larva
and was closed with a rubber stopper. The tubes were kept
Desired amounts of indomethacin, esculetin and dex-
in the dark except during a short daily observation
amethasone were first diluted in 1 ml of ethanol (70%) and
period. Larvae that died during first 24 h and tubes that
completed with distilled water to prepare solutions of the
became contaminated during the assay period were
required concentrations. Solutions of EBIs were then
excluded from the experiments. A group of larvae were
added into the diets before gel formation. The final
reared on the diet without EBIs in each experiment as no-
volumes of the diets were completed with double distilled
treatment controls. The experiments were conducted under
Y. Durmus- et al. / Journal of Insect Physiology 54 (2008) 17–24
the same laboratory conditions as mentioned for the
The larvae fed the control diet and the diets amended
Data were analyzed by one-way ANOVA. To determine
with EBIs were inoculated with BHSV-1 (2 Â 104 PFU/
significant differences between means least significant
larva) by intrahemocoelic injection as described. At 1 h PI,
difference (LSD) test () was used. When the
nodulation was assessed. Each feeding experiment was
F-estimate exceeded the probability of 0.05, the differences
replicated four times with 10 larvae. Fifth-instar larvae
were also collected for determination of phenoloxidaseactivity.
The outcomes of our control experiments are displayed
The artificial diet for the rescue experiments contained
in Untreated wasp larvae or larvae injected with
13.5 mg/100 ml AA instead of linolenic acid, the main
the indicated substances yielded about 5–20 nodules/larva.
ingredient of dietary lipid mixture. Desired amounts of
We note particularly that larvae challenged with EtOH or
dexamethasone were prepared as just described.
the EBI esculetin yielded 16 and 20 nodules/larva,
Four groups of fifth-instar wasp larvae (n ¼ 10) were
respectively, while larvae exposed to all other treatments
tested. One group of larvae was reared on control diet
produced 10 or less nodules/larva. Larvae challenged with
(insect artificial diet) as a negative control. Individuals in a
BHSV-1 at 2 Â 104 PFU/larva produced over 50 nodules/
second group were reared on the diet amended with
ethanol (EtOH, 70%) to control for the influence of EtOH. A third group was reared on the diet amended with 100 mg
3.2. The influence of viral challenge dose on nodulation
of dexamethasone. A fourth group of larvae was reared onthe diet amended with 100 mg of dexamethasone plus AA.
The data presented in show that nodulation
The larvae in these groups were challenged by injection
reactions to BHSV-1 challenge were expressed in a dose-
with BHSV-1 (2 Â 104 PFU/larva) and immune parameters
related manner in P. turionellae larvae. We recorded about
were recorded at 1 h PI. Each experiment was replicated
15 nodules/larva in control wasps which increased to about
four times with 10 larvae/replication.
55 nodules/larva in wasps treated with the highest dose of2 Â 104 PFU/larva. Each viral dose resulted in significantlyincreased nodulation and the increases obtained in a linear
2.10. Determination of phenoloxidase (PO) activity
Larvae were surface sterilized in 95% ethanol. Ten intact
fifth-instar larvae were homogenized at 4 1C by an
3.3. Time-course of nodulation: influence of BHSV-1
ultrasonic homogenizer (Bandelin Sonoplus, HD2070,Berlin, Germany) at 50 W, 40–50 s in 100 mM sodium
We recorded the influence of incubation time after
phosphate buffer (pH 7.0), and subsequently centrifuged at
infection on nodule numbers (). Highest nodulation
10,000g for 10 min. Clear supernatant was used in PO
(circa 55 nodules/larva) was recorded at 1 h PI. Longer
activity assays. The samples were diluted 1:10 (v/v)
incubation periods yielded significantly decreased numbers
in 90 ml of sodium phosphate buffer. Phenoloxidase
of nodules. We counted about 40 nodules/larva at 2, 4 and
(EC1.14.18.1) activity was assayed by using a methodmodified from and as
The results of background control experiments
supernatant (50 ml) was added to 1.5 ml glass spectro-photometer cuvettes containing 1 ml phosphate buffer
(100 mM, pH 7.0). After 20 min, 100 ml dopamine (10 mM
in sodium phosphate buffer) was added and phenoloxidase
activity (mOD/min) was determined by measuring absor-
bance at 492 nm at 5-min intervals for 30 min at 30
a UV–vis spectrophotometer (Shimadzu 1700, Kyoto,
Japan). Enzyme activity is expressed in absorbance unit
(au)/min/mg protein at 492 nm. Assays were replicated four
times each with 10 larvae. Protein concentrations in the
supernatants were determined by the method of
Fifth-instar larvae were treated as indicated and nodulation was assessed
using bovine serum albumin as quantitative
1 h later as described in Section 2. Nodulation values are mean numbers of
nodules (7S.E., n ¼ 10 larvae in all treatments).
Y. Durmus- et al. / Journal of Insect Physiology 54 (2008) 17–24
Number of Nodules Number of Nodules EtOH Virus Virus Virus Virus Virus concentrations (PFU/larva)
Fig. 1. The influence of BHSV-1 challenge dosage on nodulation reaction
Fig. 3. Influence of eicosanoid biosynthesis inhibitors on BHSV-1 induced
in P. turionellae larvae. Wasp larvae were injected with the indicated
nodulation reactions in P. turionellae larvae. Larval Group 1 (EtOH) was
dosage of BHSV-1 (distilled water for zero). Nodulation was assessed at
injected with 5 ml of 70% ethanol as a negative control. Group 2 (Virus)
1 h PI as described in Section 2. Each point represents the mean number of
was injected with our standard BHSV-1 challenge (2 Â 104 PFU/larva).
nodules (7S.E.; four replications (n ¼ 10 larvae)/treatment). Points
Groups 3, 4 and 5 were injected with, respectively, indomethacin (Indo),
annotated with the same letter are not significantly different (P40.05
esculetin (Esc) and dexamethasone (Dex), all at our standard dose of
5 mg/larva. Group 6 (Indo+virus) was treated with indomethacin prior toBHSV-1 injection. Group 7 (Esc+virus) was treated with esculetin priorto BHSV-1 injection. Group 8 (Dex+virus) was treated with dexametha-
sone prior to BHSV-1 injection. The histogram bars represents the meannumber of nodules (7S.E.; four replications (n ¼ 10 larvae)/treatment). Bars annotated with the same letter are not significantly different (P40.05
about 55 nodules/larva. Larvae treated BHSV-1 plus
indomethacin, esculetin or dexamethasone yielded very
low numbers of nodules, on par with background control
3.5. Arachidonic acid reversed the influence of
displays the results of the AA rescue experiment.
Wasp larvae reared on the control diet and challenged with
virus yielded the expected 50–55 nodules/larva. Larvaereared on diet amended with EtOH yielded about 40
Fig. 2. Time-course for nodulation reactions in response to BHVS-1challenge in P. turionellae larvae. Wasp larvae were injected with BHSV-1
nodules/larva, a significant reduction from control values.
(2 Â 104 PFU/larva). At the indicated times, PI nodulation was assessed as
Insects reared on control diet supplemented with dexa-
described in Section 2. Each point represents the mean number of nodules
methasone produced very few nodules, approximately
(7S.E.; four replications (n ¼ 10 larvae)/treatment). Points annotated
5–10/larva, in response to viral infection. Finally, wasp
with the same letter are not significantly different (P40.05 (LSD test)).
larvae reared on the AA plus dexamethasone-supplemen-ted diet yielded about 50 nodules/larva, statistically similar
6 h PI and even fewer nodules at 8 h PI. Nodulation was
assessed at 1 h PI in subsequent experiments.
3.6. The influence of per os administration of EBIs on
3.4. The influence of EBIs on nodulation reactions to viral
Orally administered EBIs influenced wasp larval nodula-
The influence of EBIs on nodulation is presented in
tion and PO activity reactions to viral infection (
. We recorded about 10–20 nodules/larva in wasps
Larvae reared on diets supplemented with dexamethasone,
challenged with EtOH, indomethacin, esculetin or dex-
indomethacin or esculetin, then challenged with viral
amethasone. Larvae challenged with BHSV-1 yielded
infection yielded fewer nodules than control larvae.
Y. Durmus- et al. / Journal of Insect Physiology 54 (2008) 17–24
maximal level very quickly, in about 1 h PI. Third, injection
treatments with indomethacin, esculetin and dexametha-
sone severely impaired nodulation reactions to viral
challenge. Fourth, the hindering influence of dexametha-sone on nodulation was reversed in wasp larvae reared on
media amended with AA, the biochemical precursor to
eicosanoid biosynthesis. Fifth, per os administration of
EBIs via culture media supplementation rendered experi-
mental larvae severely weakened in nodulation and PO
Number of Nodules
activity reactions to viral challenge. We interpret these
findings with respect to the eicosanoid hypothesis, viz.,
eicosanoids are crucial mediators of insect cellular im-
The work reported in this paper extends and strengthens
Control diet EtOH+virus Dex+virus Dex+AA+virus
the idea that eicosanoids act in insect nodulation reactions
to viral infection, recently put forth by . Although it is thought that eicosanoids act in
Fig. 4. The influence of dietary AA on the inhibitory effect ofdexamethasone (Dex) on nodulation reactions of P. turionellae larvae.
hemocytic immunity of the social hymenopteran, Apis
Larvae in Group 1 (control+virus) were reared on control diet and then
mellifera (), this is the first report of
injected with the standard BHSV-1 challenge dose. Group 2 larvae (EtOH)
eicosanoid actions in the cellular immunity of a parasitic
were reared on the diet amended with ethanol and then injected with
hymenopteran. Because most research on parasitoids is
BHSV-1. Group 3 larvae (Dex+virus) were reared on the diet amended
focused on host immune reactions to parasitoid attack, this
with Dex and then injected with BHSV-1. Group 4 larvae (Dex+AA+virus) of larvae were reared on the diet amended with Dex and AA and
work draws attention to the idea that parasitoids also
then injected with BHSV-1. Nodulation was recorded at 1 h PI. The
experience, and defense themselves from, infections. This
histogram bars represent the mean number of nodules (7S.E.; four
idea broadens appreciation of host–parasitoid relations.
replications (n ¼ 10 larvae)/treatment). Bars annotated with the same
This work also strengthens the earlier work by showing
letter are not significantly different (P40.05 (LSD test)).
that the immunity-crippling effects of dexamethasone werereversed in wasp larvae reared on basal culture medium
The influence of all three pharmaceutical compounds was
supplemented with AA. AA-driven reversals of the
expressed in a dose-related manner. For dexamethasone
dexamethasone influence on cellular immunity have been
and indomethacin, nodulation was reduced from about 50
nodules/larva in the absence of dietary EBI to less than 20
ever, this work shows that dietary administration of AA
nodules/larva in the presence of the highest dose, 100 mg/
can also reverse the dexamethasone effect. Insects are able
100 ml diet. The results with esculetin differed slightly as
to take up dietary AA, which in lengthy feeding experi-
nodulation was reduced from a high of about 60 nodules/
ments can alter the overall fatty acid profile of tissue
larva to 30 nodules/larva for larvae reared in the presence
We recorded a similar pattern for the influence of EBIs
Our data on the time-course of nodulation is interesting
on PO activity For larvae reared in the presence
in view of earlier studies of nodulation
of indomethacin and dexamethasone, PO activity at 1 h PI
was reduced in a dose-dependent manner. The results were
pattern generally recorded shows increasing numbers of
considerably different for larvae reared in the presence of
nodules appear with increased incubation times PI, up to
esculetin. In this experiment, PO activity was significantly
about 4–6 h PI. The numbers of nodules did not further
higher relative to control larvae reared in the absence of
increase following longer incubation periods. In our studies
with P. turionellae, we recorded about 55 nodules/larva at1 h PI, but the numbers of nodules decreased with longer
incubation periods. Nodules are generally lashed tointernal organs or body walls, where they remain through
In this paper, we report on the outcomes of experiments
life. They are apparently cleared from the wasp larvae after
designed to test the hypothesis that BHSV-1 challenge
the initial virus-stimulated nodulation reaction. This may
provokes eicosanoid-mediated nodulation reactions and
be a general feature of cellular immunity in parasitoid
stimulates eicosanoid-mediated increases in PO activity in
wasps. The wasps may also be subject to bacterial and
larvae of the ichneumonid wasp, Pimpla turionellae. Several
fungal infection. We do not yet know whether the wasp
points bolster the hypothesis. First, BHSV-1 challenge
larvae form nodules in reaction to bacterial or fungal
stimulated nodulation reactions that increased in a dose-
challenge, nor how long bacteria- or funal-induced nodules
related pattern with increasing viral challenge. Second, the
would remain visible within the body cavities. This remains
time-course experiment showed that nodulation reached a
Y. Durmus- et al. / Journal of Insect Physiology 54 (2008) 17–24
Indomethacin Indomethacin Esculetin Esculetin /mg protein/min) Number of nodules/Larva PO activity(au Dexamethasone Dexamethasone Treatment (g/100 mL Diet)
Fig. 5. The influence of orally administered indomethacin, esculetin and dexamethasone on P. turionellae larval nodulation reactions (Panel a) and POactivity (Panel b) reactions to intrahemocoelic BHSV-1 challenge. Larvae were reared on media amended with the indicated EBI concentration. Fifth-instar larvae were challenged by BHSV-1 injection and immune parameters were recorded at 1 h PI. Each point represents the mean number of nodules(7S.E.; four replications (n ¼ 10 larvae)/treatment). Points annotated with the same letter are not significantly different (P40.05 (LSD test)).
Our selection of EBIs sheds light on the actions of
We recently addressed the potential roles of eicosanoids
eicosanoids in nodule formation. Larvae reared in the
in PO activation and our rapidly growing body of
presence of dexamethasone, indomethacin and esculetin
knowledge on physiological defenses against viral challenge
were impaired in their nodulation reaction to BHSV-1
challenge. Dexamethasone inhibits phospholipase A2, the
commentary here. With respect to the possible roles of
first step in eicosanoid biosynthesis. Indomethacin is a
eicosanoids in viral replication in insect cells, we are now
cyclooxygenase inhibitor and esculetin is a lipoxygenase
working with a cell line established from Helicoverpa zea
inhibitor. Because both EBIs curtailed nodulation reac-
(HzAM1 cells). This cell line is non-permissive to
tions, we infer that prostaglandins (cyclooxygenase pro-
AcMNPV baculovirus replication. Our preliminary experi-
ducts) as well as various lipoxygenase products act in
ments indicate that treatments with EBIs somehow change
nodulation reactions to viral challenge, as seen in many
this non-permissive line into semi-permissive one. This
insect species following bacterial challenge (
finding, along with other work using mosquito cells (cited
). The idea that several different eicosanoid
species act in the nodulation process is consistent with
limited to prostaglandins, act in anti-viral immune func-
our understanding that nodulation is a complex process
tions at the cellular and intracellular levels.
that results from a large number of individual cell actions. We expect that some eicosanoids mediate particular steps
in nodulation while other eicosanoids act in a different setof cell actions that lead to the observable nodulation
The authors thank Dr. Aykut O¨zkul (Veterinary
Faculty, Ankara University) for the gift of the virus used
Y. Durmus- et al. / Journal of Insect Physiology 54 (2008) 17–24
in this study. This article reports the results of research
et al. (Eds.), Techniques in Insect Immunity. SOS Publications, Fair
only and mention of a proprietary product does not
constitute an endorsement or recommendation for its use
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Convenzioni doppie imposizioni Doppie imposizioni e canoni: convenzioni dell’Italia di Piergiogio Valente (*) Alla data del 15 giugno 2011, il network italiano dei trattati per evitare le doppie imposizioni in materia di imposte sul reddito e per prevenire l’evasione fiscale si è ampliato, a seguito dell’entrata in vigore del trattato col Qatar. Inoltre, è entrato in vigo