bluuebunny/crossref_metadata_2025 huggingface dataset:
Genetic immunization of mice with DNA encoding the 23 kDa transmembrane surface protein of Schistosoma japonicum (Sj23) induces antigen‐specific immunoglobulin G antibodies
Authors: WAINE  , ALARCON  , QIU  , McMANUS
Published: March 2003

The 23 kDa transmembrane surface protein of schistosomes is of recognized interest in studies of immune responsiveness in schistosomiasis. To examine the immunogenicity of the 23 kDa antigen of Schistosoma japonicum, Sj23, when delivered by genetic immunization, mice were immunized using a DNA construct containing the Sj23 cDNA under the control of a CMV promotor. Serological analysis of peripheral blood from immunized mice demonstrated that this construct was able to induce the production of antigen‐specific IgG antibodies that recognized a schistosome antigen of 23 kDa in Western blots. Despite inducing antigen‐specific antibodies, the Sj23 DNA vaccine was unable to confer protection in immunized mice subjected to challenge with S.japonicum cercariae. Appropriate engineering of the unique structure of the Sj23 kDa transmembrane protein of schistosomes may provide a novel vehicle for expressing foreign epitopes from other infectious agents or, possibly, cancer antigens, anchored to the surface of transfected cells.
Salivary gland extract from Ixodes ricinus ticks inhibits production of interferon‐γ by the upregulation of interleukin‐10
Authors: KOPECKÝ JAN , KUTHEJLOVÁ MARIE , PECHOVÁ JITKA
Published: March 2003

Tick saliva has been shown to modulate host immunity by a so far unknown mechanism. We have demonstrated an inverted effect of salivary gland extract (SGE), derived from partially fed Ixodes ricinus females, on the production of two cytokines, interferon (IFN)‐γ and interleukin (IL)‐10, in vitro. While SGE markedly suppressed the elaboration of IFN‐γ by mouse splenocytes stimulated with lipopolysaccharide (LPS), the production of IL‐10 was increased in comparison with SGE‐untreated cultures. The suppressive effect of SGE could be abolished by the addition of an IL‐10 neutralizing monoclonal antibody to splenocyte cultures. Similar results were obtained when live Borrelia afzelii spirochetes, which are transmitted in Europe by I. ricinus ticks, were used for the cytokine induction. These results suggest that tick saliva can upregulate the IL‐10 production at the tick feeding site, which consecutively inhibits the elaboration of pro‐inflammatory cytokines, for example IFN‐γ. This immunosuppression may facilitate the establishment of tick‐transmitted pathogens in the host.
Relationship between parasite‐specific antibody responses and intensity of Opisthorchis viverrini infection in hamsters
Authors: Sripa Banchob , Kaewkes Sasithorn
Published: March 2003

The kinetics of parasite‐specific antibody responses in relation to worm burden and egg output were investigated in hamsters infected with 25, 50 and 100 Opisthorchis viverrini metacercariae (MC). Levels of antibody to egg, excretory–secretory (ES) and somatic antigens were examined by ELISA on days 1, 3, 7, 14 and month 1 postinfection (p.i.), and repeated monthly up to 6 months. The antibody responses were first detected as early as 14 days after infection. Hamsters that were infected with 100 MC and 50 MC showed higher antibody levels than those of 25 MC, during early infection until 1 month p.i. Then, the antibody levels were increased rapidly to a plateau at approximately month 2 p.i. and, subsequently, were relatively stable in all groups. The average antibody levels to egg and somatic, but not to ES antigens, were significantly higher in hamsters infected with 25 MC than those of 50 MC and 100 MC. These antibody responses, particularly to egg and ES antigens, were not correlated with worm burden or egg output. Overall, higher antibody responses were found in the order: ES, somatic and egg antigens. The significant lower antibody responses in chronic and heavy infections than those with mild infection may a result of immunosuppression.
Inhibition of the antiviral action of interferon by tick salivary gland extract
Authors: Hajnická Valeria , Kocakova Pavla , Slovak Mirko , Labuda Milan , Fuchsberger Norbert , Nuttall Patricia A.
Published: March 2003

The saliva of haematophagous arthropods (e.g. mosquitoes, sandflies and ticks) contains potent immunomodulatory activities that counter their hosts' haemostatic, inflammatory and immune responses to facilitate blood‐feeding. Such effects are exploited by arthropod‐transmitted pathogens to promote their transmission. We investigated the ability of tick saliva to enhance arthropod‐borne virus (arbovirus) transmission by determining its effect on the antiviral action of murine interferon (IFN α/β). Salivary gland extract (SGE) was prepared from partially fed adult female Dermacentor reticulatus ticks that had been feeding on mice for either 3 or 5 days (SGED3 and SGED5, respectively). We demonstrated that SGE inhibits the antiviral effect of IFN as measured by a biological assay using vesicular stomatitis virus (VSV), and by two‐dimensional electrophoretic analysis of the appearance of selected VSV proteins. The most pronounced effect was observed when mouse L cells were treated with SGE prior to IFN treatment. Following pretreatment with SGE, virus multiplication (which was fully blocked by IFN treatment alone) achieved yields similar to those obtained from infected cells not treated with IFN. Contemporaneous treatment, or treatment with SGE after IFN, was less effective. In parallel with these findings, formation of early viral proteins, N (nucleocapsid protein) and P (phosphoprotein), which was blocked by IFN, was detectable following pretreatment with SGE. The ability to inhibit the antiviral action of IFN was higher for SGED3 compared to SGED5. Demonstration that tick SGE can promote virus replication by suppressing the action of IFN helps explain why ticks are such efficient vectors of arboviruses.
Dissemination of Encephalitozoon intestinalis, a causative agent of human microsporidiosis, in IFN‐γ receptor knockout mice
Authors: El Fakhry Youssef , Achbarou Abderrahim , Franetich Jean‐François , Desportes‐Livage Isabelle , Mazier Dominique
Published: March 2003

The dissemination of Encephalitozoonintestinalis, a microsporidium causing intestinal diseases and systemic infection in humans, was investigated in IFN‐γ R°/° mice. Although lesions were seen in organs of autopsied animals, the parasites were rarely detected using histological examination. Nevertheless, infection of the duodenum, liver, kidneys and lungs was demonstrated by polymerase chain reaction. This method also enabled the detection of the parasite in the brain and the heart. The development of E.intestinalis in RK13 cell cultures to which cell suspensions from liver, kidney, lung or brain of infected IFN‐γ R°/° mice were added, confirmed the spread of intestinal microsporidiosis to these organs. No dissemination was observed in wild‐type mice. These results confirm those of previous studies and emphasize the low morbidity of the infection in IFN‐γ R°/° mice and confirm the role of IFN‐γ in the control of E. intestinalis infection. These mice infected with E. intestinalis offer important information about this interesting and important parasitic disease of man and animals.
Schistosoma japonicum egg granuloma formation in the interleukin‐4 or interferon‐γ deficient host
Authors: Hirata Mizuki , Kage Masayoshi , Hara Tatsuru , Yoneda Yutaka , Zhang Mei , Fukuma Toshihide
Published: March 2003

The roles of interleukin (IL)‐4 and interferon (IFN)‐γ in Schistosoma japonicum egg granuloma formation were investigated in cercariae‐infected (infection model) or after implantation of laid parasite eggs (egg implantation model) in cytokine deficient mice. Two weeks after hepatic egg‐implantation, a markedly decreased mononuclear cell infiltration and lack of multinuclear cell formation were characteristic features in IL‐4 deficient mice. By 4 weeks (late stage), the cellular reactions around the eggs were negligible in the deficient mice. Compared to the controls, there was a drastic reduction in the production of the Th2 cytokines, IL‐4, IL‐5 and IL‐13. MCP‐1 levels were also significantly lowered. In mice experimentally infected with cercariae, granuloma cellularity in both the wild‐type and IL‐4 deficient mice at 45 days and 10 weeks postinfection was analogous to the egg implantation model at 2 and 4 weeks. Overall, the effects of IFN‐γ deficiency on granuloma induction differed markedly from the IL‐4 results. Two weeks after egg implantation, IFN‐γ deficient mice showed suppressed neutrophil response and hepatic necrosis with confluent mononuclear cell infiltration along the outer layer of granulomas. By 4 weeks, there was a decrease in cell infiltration, fibrosis and MCP‐1 production while IL‐10 production increased. While these early characteristic features for IFN‐γ deficiency were common to both the egg implantation (at 2 and 4 weeks) and cercariae infection model (at 45 days), there was a surprising difference, i.e. marked fibrosis was found in the late stages (at 10 weeks postinfection) of cercariae‐infected mice, but not in parasite egg implanted mice. Furthermore, while IL‐13 levels were unchanged, both MCP‐1 and IL‐4 production were significantly lower at 10 weeks in comparison with wild‐type. The present study clearly demonstrates the importance of both Th1 and Th2 cytokine responses in S. japonicum egg‐induced granuloma formation.
Lymphatic filariasis: parallels between the immunology of infection in humans and mice
Authors: Lawrence Rachel A. , Devaney Eileen
Published: March 2003

Mouse models of Brugia infection have provided much useful quantitative and qualitative information on the immune response elicited by different life cycle stages of filarial worms. Many parallels exist between the immune response in the mouse and the infected human and in this review we highlight areas of topical interest, including the induction of specific cytokine resposes and their role in immunomodulation and protective immunity. These studies have reinforced the concept that different life cycle stages of filarial parasites each have their own mechanism of modulating responses so that potentially inflammatory IFN‐γ responses are downregulated. While the precise mechanisms of protective immunity remain to be defined, studies in the mouse have suggested novel pathways, including a possible role for granulocytes.
Immunological genomics of Brugia malayi: filarial genes implicated in immune evasion and protective immunity
Authors: Maizels Rick M. , Blaxter Mark L. , Scott Alan L.
Published: March 2003

Filarial nematodes are metazoan parasites with genome sizes openface>  100 million base pairs, probably encoding 15 000‐20 000 genes. Within this considerable gene complement, it seems likely that filariae have evolved a spectrum of immune evasion products which underpin their ability to live for many years within the human host. Moreover, no suitable vaccine currently exists for human filarial diseases, and few markers have yet been established for diagnostic use. In this review, we bring together biochemical and immunological data on prominent filarial proteins with the exciting new information provided by the Filarial Genome Project’s expressed sequence tag (EST) database. In this discussion, we focus on those genes with the highest immunological profile, such as inhibitors of host enzymes, cytokine homologues and stage‐specific surface proteins, as well as products associated with the mosquito‐borne infective larva which offer the best opportunity for an anti‐filarial vaccine. These gene products provide a fascinating glimpse of the molecular repertoire which helminth parasites have evolved to manipulate and evade the mammalian immune response.
Progesterone fails to modulate Toxoplasma gondii replication in the RAW 264·7 murine macrophage cell line
Authors: Gay‐Andrieu Françoise , Cozon Grégoire J. N. , Ferrandiz Josette , Peyron François
Published: March 2003

Cell mediated immunity is very important for host defence against intracellular pathogens and many studies have shown the role of the production of nitric oxide (NO) by interferon (IFN)‐γ/lipopolysaccharide (LPS)‐activated macrophages. As the progesterone level increases during pregnancy in mammals, and as previous studies have shown that progesterone inhibits inducible nitric oxide synthase (iNOS) expression and NO production, we aimed to investigate whether progesterone might modulate intracellular replication of Toxoplasma gondii in macrophages. Our results showed that progesterone does not influence T. gondii replication in non‐activated RAW 264·7 cells, and although progesterone inhibits NO production induced by IFN‐γ/LPS, we observed that it fails to restore the growth of T. gondii blocked by IFN‐γ/LPS. After discussing the reasons for this apparent discrepancy, we concluded that progesterone has no direct effect on the macrophage response. The real effect of the sex steroids in T. gondii infection and their implication in clinical toxoplasmosis therefore need to be investigated further to involve wider mechanisms of the immune system.
Interferon‐γ and nitric oxide production are not required for the immune‐mediated clearance of Brugia malayi microfilariae in mice
Authors: Gray Carolyn A. , Lawrence Rachel A.
Published: March 2003

Previous research has shown that Brugia malayi microfilariae (Mf) primarily induce type 1 cytokine production, and that in‐vitro nitric oxide (NO) can mediate Mf killing. This study addresses the role of interferon (IFN)‐γ‐mediated immune responses in the clearance of Mf from fast‐clearing (CBA/Ca) and slow‐clearing (C57Bl/6) mouse strains. Analysis of spleen cell cytokine production at early timepoints p.i. showed that Mf‐induced IFN‐γ and nitrite (NO−) levels were significantly greater in CBA/Ca mice than C57Bl/6 mice. However, in‐vivo neutralization of IFN‐γ or inhibition of NO− production in CBA/Ca mice did not alter Mf survival kinetics. Similarly, the rate of Mf clearance in both C57Bl/6 mice lacking the IFN‐γ gene and (C57Bl/6 × 129) mice deficient in the receptor for IFN‐γ was similar to that of wild‐type animals. Furthermore, the dramatic abrogation of NO− production in IFN‐γR−/− mice suggests that Mf clearance in slow‐clearing mouse strains is also independent of NO− production. Thus, in both rapid‐clearing and slow‐clearing mouse strains, IFN‐γ‐mediated mechanisms are not a requirement for Mf clearance from the bloodstream.
Divergent expression of inflammatory dermal chemokines in cutaneous leishmaniasis*
Authors: Ritter Uwe , Körner Heinrich
Published: March 2003

Human leishmaniasis is caused by protozoan Leishmania (L.) parasites and comprises a heterogeneous group of clinical appearances ranging from visceral to cutaneous leishmaniasis. In the New World, L. mexicana mediates American cutaneous leishmaniasis, one of the most common forms of this disease. Two different disease progressions can be observed: (i) self‐healing localized cutaneous leishmaniasis (LCL) and (ii) progressive diffuse cutaneous leishmaniasis (DCL). These different forms are associated with a T helper 1 (Th1) or Th2 response, respectively, and are additionally characterized by opposing dermal chemokine profiles. Lesions of LCL show high expression of CCL2/MCP‐1, CXCL9/MIG, CXCL10/IP‐10 and only low amounts of CCL3/MIP‐1α. In contrast, lesions of chronic DCL are dominated by the expression of CCL3/MIP‐1α. This finding implies that CCL2/MCP‐1 contributes to the healing process. Indeed, CCL2/MCP‐1 induces leishmanicidal activities in human monocytes in contrast to CCL3/MIP‐1α. This effect is enhanced by interferon‐γ and abrogated by interleukin‐4. In the murine model of leishmaniasis, the impact of CCL2/MCP‐1 is well documented. Normally resistant mice become susceptible for Leishmania infections if CCR2, the receptor for CCL2/MCP‐1, is knocked out. Based on this evidence, we propose that tissue specific expression of these small molecules actively regulates cell traffic and tissue localization of effector cells and, additionally, has direct immunological effects.
Precocene II modifies maternal responsiveness in the burrower bug, Sehirus cinctus (Heteroptera)
Authors: KIGHT SCOTT L.
Published: March 2003

Abstract. The anti‐Juvenile Hormone agent precocene II was used to investigate the relationship of corpora allata activity to subsocial behaviour in a burrower bug Sehirus cinctus Palisot (Heteroptera: Cydnidae). Egg‐brooding females treated with a range of dosages of precocene II exhibited reliably depressed maternal defensive behaviour when treated with at least 70 μg of precocene II, but attraction to eggs was only depressed at higher dosages. This effect was not due to precocene II toxicity, as demonstrated by the prevention of depression effects through simultaneous treatments of precocene II and the Juvenile Hormone analogue methoprene. Methoprene, however, failed to reinstate maternal responsiveness in maternally depressed females that had been previously treated with precocene II. This study provides the first clear evidence that insect parental behaviour can be modified by treatment with anti‐Juvenile Hormone agents, and suggests that the role of the corpora allata in governing care in S. cinctus is different from that of other maternal insects, such as earwigs.
Flight muscle changes in male pine engraver beetles during reproduction: the effects of body size, mating status and breeding failure
Authors: ROBERTSON IAN C.
Published: March 2003

Abstract. In a pattern that is typical for bark beetles, the lateralis medius flight muscle of male pine engravers, Ips pini Say (Coleoptera: Scolytidae), was found to decrease four‐fold in volume (from mean ± SE = 1.36 ± 0.06 × 10−2 mm3 to 0.34 ± 0.06 × 10−2 mm3) within five days of the initiation of breeding galleries, and then to regenerate gradually to functional capacity during subsequent weeks. Although there was considerable variation in the timing and extent of flight muscle regeneration in males, this variation was not a consequence of differences between small (length < 4.0 mm) and large (length ≥ 4.0 mm) males. Two subsequent experiments revealed that male pine engravers can control the timing of flight muscle regeneration. In the first experiment, the flight muscles of males that were denied mates degenerated within 5 days of gallery initiation, but then showed complete regeneration 5 days later. In the second experiment, mated males that were removed from their breeding galleries (to simulate breeding failure) also showed extensive muscle degeneration 5 days after gallery initiation, but then regenerated their flight muscles to functional capacity by the tenth day. The ability of males to regenerate their flight muscles in response to conditions at the gallery is probably adaptive because it allows them to fly in search of new breeding opportunities when they are unable to attract mates or when breeding attempts fail.
Do large bushcrickets have more sensitive ears? Natural variation in hearing thresholds within populations of the bushcricket Requena verticalis (Listroscelidinae: Tettigoniidae)
Authors: BAILEY WINSTON
Published: March 2003

The auditory spiracle of tettigoniid Orthoptera influences hearing threshold and, for the most part, individuals with larger auditory spiracles have lower hearing thresholds; they are more sensitive. Hearing thresholds of both sexes of the bushcricket, Requena verticalis Walker (Orthoptera; Tettigoniidae; Listroscelidinae), were measured at the male call’s carrier frequency and were found to correlate with spiracle dimension. In turn, spiracle dimension correlates with the size of the insect as measured by pronotum length. The best frequency of hearing is close to 16 kHz and this appears to be independent of size. Males show a higher variation in threshold than females and this was reflected in a trend toward lower variance in spiracle size in females.

To test the effects of size on sensitivity, spiracle size was manipulated by partially blocking it. Blocking the spiracle decreases sensitivity to high rather than low frequencies. As in other tettigoniids, the spiracle and associated auditory system act as a high‐pass filter. Within and between sex differences in hearing sensitivity were compared with differences in male call intensity. It is argued that sensitivity to sounds associated with mating should be as much under sexual selection as the sexual calls of males.
The decision to reject an oviposition site: sequential analysis of the post‐alighting behaviour ofDelia floralis
Authors: Hopkins R. J. , Wright F. , Birch A. N. E. , And . , Mckinlay R. G.
Published: March 2003

Abstract.The post‐alighting behaviour of gravid female turnip root fly, Delia floralis (Fallén) (Diptera: Anthomyiidae), was observed in the laboratory, using four plant genotypes differing in antixenotic resistance, to stimulate a range of oviposition‐related behavioural events. Analysis of the behavioural sequences of individual female flies suggested that during the post‐alighting behaviour of D. floralis, the decision to reject a highly resistant plant was predominantly based on plant cues received during a stationary period immediately after landing on the leaf (the leaf contact phase). Female flies that rejected a plant immediately after the leaf contact phase did so after spending approximately twice as long in the leaf contact phase as those flies that continued to explore the plant. On a plant genotype of intermediate susceptibility, D. floralis females on the stem of the plants increased proboscis extension. The mechanisms involved in early host plant rejection decisions and the possible ecological advantages of such behaviour patterns to female flies seeking suitable oviposition sites are explored. The potential advantages of using detailed studies of individual behaviour sequences to focus studies seeking to elucidate chemical oviposition stimuli on the plant’s surface are also discussed.
The effect of ovariectomy on reproductive behaviour and physiology of adult female ring‐legged earwigs, Euborellia annulipes
Authors: Rankin Susan M. , Mcquiston Susan J. , Jackson Ellen S.
Published: March 2003

The effect of ovariectomy on feeding, mating, Juvenile Hormone (JH) production, and maternal behaviour was assessed in female ring‐legged earwigs, Euborellia annulipes (Lucas) (Dermaptera: Carcinophoridae), during the first 16 days of adult life (the first gonadotrophic cycle and early brooding).

Ovariectomy of 2‐day‐old adults did not affect weight gain, nor did it alter mating behaviour on day 7. Similarly, ovariectomy did not prevent the increase in JH biosynthesis that accompanies vitellogenesis in this species, which suggests a cycle of JH production that is not dependent on the presence of the ovaries.

Both ovariectomy and mating status affected feeding behaviour. Most introduced eggs were consumed (i.e. disappeared) within 24 h, and younger (7‐day‐old) females consumed more eggs than did older ones. However, 12‐day‐old intact virgins and 16‐day‐old ovariectomized, mated females consumed fewest eggs, and allowed some hatching. Thus, ovariectomy did not abolish changes in feeding behaviour that normally accompany reproduction but, instead, appeared to delay the reduction in feeding that normally accompanies the completion of the cycle of egg development. By contrast, mating enhanced the reduction in feeding late in the reproductive cycle.

Mating significantly enhanced maternal behaviour in both ovariectomized and sham‐operated females. Hatching success from egg clutches introduced to day 16 virgin or mated females that had been ovariectomized or sham‐operated on day 2, was significantly greater in the mated groups.
Expression of a life‐history trade‐off in a seed beetle depends on environmental context
Authors: Messina Frank J. , Slade Andrea F.
Published: March 2003

Within populations of the seed beetleCallosobruchus maculatus(F.) (Coleoptera: Bruchidae), female longevity is positively correlated with fecundity, both phenotypically and genetically. Yet manipulations of egg‐laying rate (through deprivation of seeds or mates) consistently suggest a trade‐off between these traits. In this study, females were exposed to four levels of seed availability and the relationship between fecundity and longevity was examined both across and within environments. The expected trade‐off was observed across environments, as females with few or no seeds laid fewer eggs and lived longer than females with many seeds. Within environments, however, the relationship was inconsistent; individual longevity and fecundity were positively correlated when seeds were abundant, uncorrelated when seeds were few and negatively correlated when seeds were absent. Body mass at adult emergence was positively correlated with fecundity, but its effect was stronger when seeds were present than when they were absent. After the effects of mass were statistically controlled, longevity and fecundity remained positively correlated among females with many seeds and negatively correlated among those without seeds. Thus, even a single technique (phenotypic correlation) can produce divergent conclusions about the ‘cost of reproduction’ in insects. The reversal in the correlation appears to depend on variation in reproductive allocation; when seeds are scarce or absent, differences in reproductive effort among individuals may be large enough to overwhelm differences in resource acquisition.
Effects of sugar feeding on carbohydrate and lipid metabolism in a parasitoid wasp
Authors: Olson D.A.W.N. M. , Fadamiro Henry , Lundgren J.O.nathan G. , Heimpel George E.
Published: March 2003

Lifetime patterns of carbohydrate and lipid metabolism were compared in starved and sucrose‐fed adults of the parasitoid Macrocentrus grandii (Goidanich) (Hymenoptera: Braconidae). As expected, sucrose‐fed individuals lived longer than did starved individuals. Macrocentrus grandii males and females eclosed with levels of simple storage sugars (presumably primarily trehalose) and glycogen that were below maximum levels recorded from sucrose‐fed parasitoids. Both of these nutrients dropped to very low levels in starved individuals within 4 days post‐emergence and were maintained at high levels in sucrose‐fed individuals throughout their lives. Lipid reserves at emergence represented the highest lipid levels for both sexes in the two diet treatments, with levels declining over the lifetimes of males and females from both diet treatments. Our results therefore suggest that dietary sucrose is used to synthesize trehalose and glycogen, but not lipids in M. grandii. Also, in contrast to the patterns observed for the simple sugars and glycogen, lipid levels in starved individuals did not drop below levels observed in sugar‐fed individuals. The average number of mature eggs carried by females at emergence was 33 and increased to approximately 85 in sucrose‐fed and 130 in starved females by the age of 5 d in the absence of hosts. The egg maturation rate was therefore higher in starved than in sugar‐fed females. Potential explanations for this unexpected result are discussed.
Navigating desert ants (Cataglyphis fortis) learn to alter their search patterns on their homebound journey
Authors: Cheng Ken , Wehner Rüdiger
Published: March 2003

In navigating home, desert ants first run off a global vector estimated on their outbound journey, and then engage in systematic search consisting of ever‐increasing loops interrupted by returns to the starting point of search. Desert ants (Cataglyphis fortis;Wehner, 1983) were trained to travel 6 m down a channel to a food source. Different groups of ants were trained to return home in another channel, from distances of 6 m (control), 9 m or 12 m. Ants at the feeder were then tested in a long test channel. The measure of where the ants first turned back on a test gave an estimate of the length of the global vector calculated on their outbound trip. The median distance of search on a 5‐min test gave an estimate of the centre of the search pattern. Relative to controls, the experimental ants did not increase their estimated length of global vector, but changed their search patterns, searching on average further from the start than the controls. Tests of the outbound journey, however, revealed no differences between groups. Desert ants can learn to modify their search pattern based on experience.
Comparing heat stress effects on male‐fertile and male‐sterile tomatoes
Authors: Peet M. M. , Sato S. , Gardner R. G.
Published: March 2003

To separate the effects of heat stress on male and female reproductive tissues, male‐sterile (MSs) and male‐fertile tomatoes (MFs) were placed in growth chambers at 12 h day/12 h night temperatures of 28/22, 30/24 or 32/26 °C from flower appearance to seed maturation (daily mean temperatures of 25, 27 or 29 °C). Pollen from MFs was applied individually to MS flowers. As MFs were self‐pollinated, heat stress was experienced by both male and female tissues. At growth temperatures of 29 °C fruit number, fruit weight per plant, and seed number per fruit were only 10%, 6·4% and 16·4%, respectively, compared with those at 25 °C. Heat stress also adversely affected fruitset in MSs, especially when experienced by donor pollen. No fruit at all developed on MSs receiving pollen produced at 29 °C, even when ovule development, pollen germination and subsequent embryo development all took place at 25 °C. Effects on fruitset in MSs were reduced if donor pollen had not experienced heat stress. MSs grown at 29 °C but receiving pollen developing at 25 °C produced 73% as much fruit (both on number and weight basis), had 40% as high fruitset and produced 87% of the seed per fruit as MSs grown at 25 °C. This use of male‐sterile and male‐fertile lines of tomato provides new evidence that impairment of pollen and anther development by elevated temperature will be an important contributing factor to decreased fruit set in tomato, and possibly other crops, with global warming.
Photosynthetic pigment concentration, organization and interconversions in a pale green Syrian landrace of barley (Hordeum vulgare L., Tadmor) adapted to harsh climatic conditions
Authors: Tardy F. , Créach A. , Havaux M.
Published: March 2003

Tadmor is a Syrian barley landrace that has adapted to semi‐arid environments. Its leaves are pale green because of a 30% decrease in the chlorophyll and the carotenoid content of the chloroplasts (leading to a 7·5% decrease in light absorption) compared with barley genotypes that are not adapted to harsh Mediterranean climatic conditions (e.g. Plaisant). This difference in pigment content was attenuated during growth of the plants in strong light, but was strongly amplified when strong light was combined with a high growth temperature. The low pigment content of Tadmor leaves was not associated with significant changes in the pigment distribution between the photosystems or between the reaction centres of the photosystems and their associated chlorophyll antennae. No significant difference in the photosynthetic activity (O2 production per unit absorbed light) was observed between Tadmor and Plaisant. The conversion of violaxanthin to zeaxanthin in strong light and its reversal in darkness were much faster and operated at a higher capacity in Tadmor leaves compared with Plaisant leaves, resulting in an increased photostability of photosystem II in the former leaves. The accelerated xanthophylls interconversion in the Syrian landrace was associated with, and possibly related to, an increased fluidity of the thylakoid membranes. The lipid peroxide level was lower in Tadmor compared with Plaisant. In contrast, no difference was found in the non‐photochemical quenching of chlorophyll fluorescence between the two barley genotypes. The data indicate that the pale green Syrian landrace is equipped to survive excessive irradiance through a passive reduction of the light absorptance of its leaves, which mitigates the heating effects of strong light, and through the active protection of its photochemical apparatus by a rapid xanthophyll cycling.
Phosphorus compartmentation in Pinus serotina Michx. (pond pine); observations from in vivo nuclear magnetic resonance spectroscopy
Authors: Ayling S. M. , Topa M. A.
Published: March 2003

31P nuclear magnetic resonance (NMR) spectroscopy was used to estimate the amount of inorganic phosphate (Pi) present in the cytoplasm and vacuole of root tips and subapical root segments of pond pine (Pinus serotina Michx.). In root tips of seedlings grown with 100 mmol m–3P (HP) the cytoplasmic Pi content, on a root volume basis, was ≈ 1·5 μmol cm–3 and the vacuolar Pi content, on a root volume basis, was ≈ 3·4 μmol cm–3. In root tips from Pi starved seedlings the cytoplasmic Pi content, on a root volume basis, was ≈ 0·75 μmol cm–3; vacuolar Pi was too low to be reliably estimated. Similar results were obtained with subapical root segments; the Pi concentration in the cytoplasm was maintained at around 2 mol m–3 while that in the vacuole varied with Pi supply. This work demonstrates for the first time that quantitative measurements of the subcellular compartmentation of Pi can be made in young tissues of a woody species. The results indicate that cytoplasmic Pi levels are maintained across a range of external Pi supplies probably by withdrawing Pi stored in the vacuole.
Induction of nitrate uptake and nitrate reductase activity in trembling aspen and lodgepole pine
Authors: Min X. , Siddiqi M. Y. , Guy R. D. , Glass A. D. M. , Kronzucker H. J.
Published: March 2003

13NO3– influx into the roots and in vivo nitrate reductase activity (NRA) in the roots and leaves have been measured in trembling aspen (Populus tremuloides Michx.) and lodgepole pine (Pinus contorta Dougl.) seedlings after exposure to either 0·1 or 1·5 mol m–3 NO3– for varying periods up to 20 d. Both NO3– influx and NRA were inducible in these species and, in trembling aspen, peak induction of nitrate influx and NRA were achieved within 12 h, compared to 2–4 d for influx and 4–12 d for NRA in lodgepole pine. In trembling aspen, ≈ 30% of the total 13N absorbed during a 10 min influx period followed by 2 min of desorption was translocated to the shoot. In lodgepole pine, by contrast, translocation of 13N to the shoot was undetectable during the same time period. Root NRA as well as NO3– influx from 0·1 mol m–3 NO3– were substantially higher in trembling aspen than in lodgepole pine at all stages of NO3– exposure, i.e. during the uninduced, the peak induction, and steady‐state stages. In order to examine whether the lower rates of NO3– influx and NRA were related to proportionately fewer young (unsuberized) roots in lodgepole pine, we determined these parameters in young and old (suberized) roots of this species separately. Induction of influx and NRA were initially greater in young roots but at steady‐state there were only minor differences between the young and the old roots. However, even the elevated initial rates in the young roots of lodgepole pine were substantially lower than those of aspen. In pine, influx at 1·5 mol m–3 NO3– was ~ 6‐fold higher than at 0·1 mol m–3 NO3– and appeared to be mostly via a constitutive system. By contrast, in aspen, steady‐state influxes at 0·1 and 1·5 mol m–3 were not significantly different, being similar to the rate attained by pine at only the higher [NO3–]. In aspen, leaf NRA was ~ 2‐fold higher than that of roots. In lodgepole pine NRA of the needles was below the detection limit. These results show that trembling aspen seedlings are better adapted for NO3– acquisition and utilization than lodgepole pine seedlings.
Dual turgor regulation response to hypotonic stress in Lamprothamnium papulosum
Authors: BEILBY M. J. , CHERRY C. A. , SHEPHERD V. A.
Published: March 2003

Cells of the salt‐tolerant charophyte Lamprothamnium respond differently to hypotonic challenge according to their position on the plant (i.e. cell age). Differences in electrophysiological response are coupled with differences in cell fine structure, and the presence or absence of extracellular mucilage. (1) Young, apical (fast‐regulating, FR) cells respond with sudden cessation of cyclosis, depolarization to –50 mV (in some cells by more than 100 mV) and increase in membrane conductance by up to an order of magnitude. Intracellular [K+]v, [Na+]v and [Cl–]v decrease 1 h after hypotonic challenge. Patch‐clamping cytoplasmic droplets reveals two types of K+ channel, 150 pS and 35 pS, and a small conductance Cl– channel, 35 pS (conductances at estimated tonoplast resting potential between zero and 20 mV). Extracellular mucilage is thin (< 5 μm thick) or lacking, similar to freshwater Chara. Unlike freshwater charophytes these cells have a canalicular vacuolar system of large surface area and compartment the fluorochrome 6 carboxyfluorescein in the cytoplasm rather than the vacuolar system. (2) Older basal (slow‐regulating, SR) cells do not cease streaming on hypotonic challenge and depolarize only slightly (by approximately 20 mV) with small or no change in membrane conductance. After 1 h the intracellular [K+]v, [Na+]v and [Cl–]v scarcely change. Patch‐clamping cytoplasmic droplets reveals two types of K+ channel, medium conductance 90 pS and low conductance (as in FR cells). The large conductance K+ channel was not observed. The Cl– channel was more active in SR cells. The cells were coated with extracellular mucilage more than 10 μm thick. In a similar manner to freshwater Chara, these cells compartment 6 carboxyfluorescein in a large central vacuole. In the older cells, making up the bulk of any given plant, the simultaneous development of extracellular mucilage and a large central vacuole which compartments 6 carboxyfluorescein is associated with a minimal electrophysiological response to hypotonic challenge. The significance of these findings for salt‐tolerance is discussed.
An analysis of the dynamic response of stomatal conductance to a reduction in humidity over leaves of Cedrella odorata
Authors: Jarvis A. J. , Young P. C. , Taylor C. J. , Davies W. J.
Published: March 2003

Single leaves of 3‐month‐old Cedrella odorata seedlings were exposed to a step reduction in the ambient dew point. The resultant time series of dynamic variations in leaf surface water vapour concentration, leaf surface water vapour concentration gradient, transpiration rate and stomatal conductance to water vapour, are analysed using the data‐based mechanistic (DBM) modelling methodology of Young (e.g.
Young & Lees 1992;
Minchin et al. 1996
). It is shown that the identified second‐order, dynamic model between transpiration rate (as the input) and stomatal conductance (as the output) provides an appropriate, physiologically meaningful, description of the system. In particular, the dynamic relationship between these two variables is remarkably linear and can be resolved in terms of two parallel, first‐order, subsystems; a model which complements the results of
Cowan (1977) for cotton. The model is also compared with the recently published simulation model of
Haefner, Buckley & Mott (1997).
Transport constraints on water use by the Great Basin shrub, Artemisia tridentata
Authors: Kolb  , Sperry
Published: March 2003

As soil and plant water status decline, decreases in hydraulic conductance can limit a plant’s ability to maintain gas exchange. We investigated hydraulic limitations for Artemisia tridentata during summer drought. Water use was quantified by measurements of soil and plant water potential (Ψ), transpiration and leaf area. Hydraulic transport capacity was quantified by vulnerability to water stress‐induced cavitation for root and stem xylem, and moisture release characteristics for soil. These data were used to predict the maximum possible steady‐state transpiration rate (Ecrit) and minimum leaf xylem pressure (Ψcrit). Transpiration and leaf area declined by ~ 80 and 50%, respectively, as soil Ψ decreased to –2·6 MPa during drought. Leaf‐specific hydraulic conductance also decreased by 70%, with most of the decline predicted in the rhizosphere and root system. Root conductance was projected to be the most limiting, decreasing to zero to cause hydraulic failure if Ecrit was exceeded. The basis for this prediction was that roots were more vulnerable to xylem cavitation than stems (99% cavitation at –4·0 versus –7·8 MPa, respectively). The decline in water use during drought was necessary to maintain E and Ψ within the limits defined by Ecrit and Ψcrit.
Resistance of cold‐hardened winter rye leaves (Secale cereale L.) to photo‐oxidative stress
Authors: Streb P. , Shang W , Feierabend J
Published: March 2003

Catalase and photosystem II (PSII) were strongly inactivated during exposure to 4 °C and moderate light in 22 °C‐grown non‐hardened leaves (NHL) of winter rye (Secale cereale L.), but highly resistant to photo‐inactivation at low temperature in 4 °C‐grown cold‐hardened leaves (CHL). Resistance of CHL to chilling‐induced photo‐inactivation of catalase and PSII depended partially on more efficient de novo synthesis at 4 °C and partially on improved protection. Lower rates of chloroplast‐mediated inactivation of catalase in vitro indicated that less reactive oxygen was released by chloroplasts from CHL than by chloroplasts from NHL. The contents of xanthophyll cycle carotenoids, α‐tocopherol, ascorbate, glutathione, the activities of superoxide dismutase and glutathione reductase, and the tolerance against paraquat‐induced photo‐oxidative damage were greatly increased in CHL, relative to NHL. Zeaxanthin‐related thermal energy dissipation was only of minor importance for paraquat‐tolerance and protection of catalase in CHL. When CHL were transferred to a higher temperature of 22 °C the increased resistance to photo‐inactivation of catalase and PSII and the increased paraquat‐tolerance were largely lost within 3 d, whereas most non‐enzymic and enzymic antioxidants retained higher levels than in NHL. The decline of resistance to photodamage during dehardening was not related to concomitant changes of antioxidants or antioxidative enzymes.
Light use efficiency of dry matter gain in five macro‐lichens: relative impact of microclimate conditions and species‐specific traits
Authors: Palmqvist K. , Sundberg B.
Published: March 2003

Relations between irradiance (I) and lichen growth were investigated for five macro‐lichens growing at two sites in Sweden. The lichens represented different mycobiont–photobiont associations, two morphologies (foliose, fruticose) and two life forms (epiphytic, terricolous). The lichens were transplanted at two geographically distant sites in Sweden (1000 km apart) from Sept 1995 to Sept 1996 in their typical microhabitats, where microclimate and growth were followed. Between April/May and Sept 96, the terricolous species had a dry matter gain of 0·2 to 0·4 g (g DW)–1 and the epiphytes 0·01 to 0·02 g (g DW)–1. When related to area, growth amounted to 30 to 70 g m−2 for the terricolous species and to 1 to 4 g m−2 for the epiphytes. There was a strong correlation between growth and intercepted irradiance when the lichens were wet (Iwet), with 0·2 to 1·1 g lichen dry matter being produced per MJ solar energy. Across the 10 sets of transplants, light use efficiencies of dry matter yield (e) ranged between 0·5 and 2%, using an energy equivalent of 17·5 kJ g−1 of lichen dry matter. The higher productivity of the terricolous species was due to longer periods with thallus water contents sufficient for metabolic activity and because of the higher mean photon flux densities of their microhabitat. A four‐fold difference in photosynthetic capacity among the species was also important. It is concluded that lichen dry matter gain was primarily related to net carbon gain during metabolically active periods, which was determined by light duration, photon flux density and photosynthetic capacity.
Variation in dynamics of phytochrome A inArabidopsisecotypes and mutants
Authors: Eichenberg K. , Hennig L. , Martin A. , Schäfer E.
Published: March 2003

Phytochromes are photoreceptors in plants which can exist in two different conformations: the red light‐absorbing form (Pr) and the far‐red light‐absorbing form (Pfr), depending on the light quality. The Pfrform is the physiologically active conformation. To attenuate the Pfrsignal for phytochrome A (phyA), at least two different mechanisms exist: destruction of the molecule and dark reversion. Destruction is an active process leading to the degradation of Pfr. Dark reversion is the light‐independent conversion of physiologically active Pfrinto inactive Pr. Here, we show that dark reversion is not only an intrinsic property of the phytochrome molecule but is modulated by cellular components. Furthermore, we demonstrate that dark reversion of phyA may be observed inArabidopsisecotype RLD but not in otherArabidopsisecotypes. For the first time, we have identified mutants with altered dark reversion and destruction in a set of previously isolated loss of function PHYA alleles (Xuet al. Plant Cell1995, 7, 1433–1443). Therefore, the dynamics of the phytochrome molecule itself need to be considered during the characterization of signal transduction mutants.
Stomatal responses to non‐local changes in PFD: evidence for long‐distance hydraulic interactions
Authors: Buckley Thomas N. , Mott Keith A.
Published: March 2003

Interactions among stomata within a single areole have recently been reported, and evidence suggests that hydraulic mechanisms may be responsible for these interactions. Such interactions may play a role in patchy stomatal behaviour by coordinating stomatal behaviour within areoles. However, models suggest that longer‐distance interactions may be required to produce the large‐scale discoordination that is characteristic of stomatal patchiness. This study was undertaken to characterize long‐distance interactions between ‘artificial patches’ of stomata under varying conditions of evaporative demand and soil water stress. Gas‐exchange was monitored in two adjacent regions (‘patches’) of a wheat leaf by two independent gas mixing and analysis systems. When photon flux density (PFD) was changed in only one of these patches, stomatal conductance responded in both patches in a manner consistent with hydraulic interactions propagated by changes in xylem water potential. These data are discussed in the context of mechanisms for patchy stomatal conductance and implications for the design and analysis of gas‐exchange experiments.
Physiological factors limit fruit set of tomato (Lycopersicon esculentum Mill.) under chronic, mild heat stress
Authors: Sato S. , Peet M. M. , Thomas J. F.
Published: March 2003

The effects of chronic, mild heat stress on fruit set, fruit production, release of pollen grains, photosynthesis, night respiration and anther dehiscence were examined in tomatoes (Lycopersicon esculentum Mill.) differing in high‐temperature sensitivity. Plants were grown under three temperature regimes: (1) 28/22 or 26/22 °C (optimal temperature); (2) 32/26 °C (high temperature); and (3) 32/26 °C day/night temperatures relieved at 28/22 °C for 10 d before anthesis, then returned to 32/26 °C (relieving treatment). FLA 7156 was the only cultivar with fruit set at 32/26 °C. All five cultivars, however, had fruit set under the relieving treatment (RT). The longer the relief, the higher the percentage of fruit set. Longer periods of relief also increased the number of pollen grains released, and linear regression analysis showed a significant relationship between the number of pollen grains released and the percentage of fruit set. Germination of pollen grains was also lowered in high‐temperature‐grown plants. The number of pollen grains produced, photosynthesis and night respiration did not limit fruit set under chronic, mild heat stress, however. This suggested that cultivar differences in pollen release and germination under heat stress are the most important factors determining their ability to set fruit.