Correlated insecticide cross-resistance in azinphosmethyl resistant codling moth (Lepidoptera: Tortricidae)

Resistance to several classes of insecticides was correlated with azinphosmethyl resistance in codling moth, Cydia pomonella (L.), in California. In tests of laboratory and field populations, cross-resistance was positively correlated with azinphosmethyl and two organophosphates (diazinon, phosmet), a carbamate (carbaryl), a chlorinated hydrocarbon (DDT), and two pyrethroids (esfenvalerate and fenpropathrin). Additionally, negatively correlated cross-resistance was identified between azinphosmethyl and two other organophosphates, chlorpyrifos and methyl parathion. Patterns of resistance observed in laboratory colonies were confirmed with field bioassays. In bioassays of field populations, azinphosmethyl resistance was observed to increase from 1991 to 1993, although levels of resistance remained < 13-fold. Because orchards with azinphosmethyl resistance have had difficulties with suppression of codling moth, and cross-resistance was found for all tested classes of insecticides, strategies for managing resistance will need to be developed so as to protect current and future control tactics. The two insecticides with negatively correlated cross-resistance are discussed as potential tools for resistance management.     

Tolerance to herbivory by a stemboring caterpillar in architecturally distinct maizes and wild relatives

In a screenhouse experiment in southwest Mexico, we infested two maize cultivars, a land-race and a modern high-yielding variety, and two wild teosintes, Zea diploperennis and Zea mays parviglumis, with newly hatched larvae of the stemborer, Diatraea grandiosella. While subsequent damage levels, when corrected for differences in plant size, were highest in the wild perennial, Zea diploperennis, this taxon showed the lowest absolute and proportional reductions in growth and reproduction, i.e., it was most tolerant to the damage. Higher growth rates were not associated with tolerance. Rather, a greater number of tillers and leaves in the wild taxa allowed for compartmentalization of damage and greater developmental plasticity. These results, when combined with previous findings on effective defense patterns, indicate that tolerance in maizes and wild relatives may be positively associated with defense against stemboring by the same insect. Because the probable mechanisms for defense (tissue fiber) and tolerance (plant architecture) are unrelated, a positive association is contrary to the predictions of some optimal defense theories, which posit a negative relationship between tolerance and defense.     

Warming alters coupled carbon and nutrient cycles in experimental streams

Although much effort has been devoted to quantifying how warming alters carbon cycling across diverse ecosystems, less is known about how these changes are linked to the cycling of bioavailable nitrogen and phosphorus. In freshwater ecosystems, benthic biofilms (i.e. thin films of algae, bacteria, fungi, and detrital matter) act as biogeochemical hotspots by controlling important fluxes of energy and material. Understanding how biofilms respond to warming is thus critical for predicting responses of coupled elemental cycles in freshwater systems. We developed biofilm communities in experimental streamside channels along a gradient of mean water temperatures (7.5–23.6 °C), while closely maintaining natural diel and seasonal temperature variation with a common water and propagule source. Both structural (i.e. biomass, stoichiometry, assemblage structure) and functional (i.e. metabolism, N₂‐fixation, nutrient uptake) attributes of biofilms were measured on multiple dates to link changes in carbon flow explicitly to the dynamics of nitrogen and phosphorus. Temperature had strong positive effects on biofilm biomass (2.8‐ to 24‐fold variation) and net ecosystem productivity (44‐ to 317‐fold variation), despite extremely low concentrations of limiting dissolved nitrogen. Temperature had surprisingly minimal effects on biofilm stoichiometry: carbon:nitrogen (C:N) ratios were temperature‐invariant, while carbon:phosphorus (C:P) ratios declined slightly with increasing temperature. Biofilm communities were dominated by cyanobacteria at all temperatures (>91% of total biovolume) and N₂‐fixation rates increased up to 120‐fold between the coldest and warmest treatments. Although ammonium‐N uptake increased with temperature (2.8‐ to 6.8‐fold variation), the much higher N₂‐fixation rates supplied the majority of N to the ecosystem at higher temperatures. Our results demonstrate that temperature can alter how carbon is cycled and coupled to nitrogen and phosphorus. The uncoupling of C fixation from dissolved inorganic nitrogen supply produced large unexpected changes in biofilm development, elemental cycling, and likely downstream exports of nutrients and organic matter.     

Vaccination against canine distemper virus infection in infant ferrets with and without maternal antibody protection, using recombinant attenuated poxvirus vaccines

Canine distemper virus (CDV) infection of ferrets is clinically and immunologically similar to measles, making this a useful model for the human disease. The model was used to determine if parenteral or mucosal immunization of infant ferrets at 3 and 6 weeks of age with attenuated vaccinia virus (NYVAC) or canarypox virus (ALVAC) vaccine strains expressing the CDV hemagglutinin (H) and fusion (F) protein genes (NYVAC-HF and ALVAC-HF) would induce serum neutralizing antibody and protect against challenge infection at 12 weeks of age. Ferrets without maternal antibody that were vaccinated parenterally with NYVAC-HF (n = 5) or ALVAC-HF (n = 4) developed significant neutralizing titers (log(10) inverse mean titer +/- standard deviation of 2.30 +/- 0.12 and 2.20 +/- 0.34, respectively) by the day of challenge, and all survived with no clinical or virologic evidence of infection. Ferrets without maternal antibody that were vaccinated intranasally (i.n.) developed lower neutralizing titers, with NYVAC-HF producing higher titers at challenge (1.11 +/- 0.57 versus 0.40 +/- 0.37, P = 0.02) and a better survival rate (6/7 versus 0/5, P = 0.008) than ALVAC-HF. Ferrets with maternal antibody that were vaccinated parenterally with NYVAC-HF (n = 7) and ALVAC-HF (n = 7) developed significantly higher antibody titers (1.64 +/- 0. 54 and 1.28 +/- 0.40, respectively) than did ferrets immunized with an attenuated CDV vaccine (0.46 +/- 0.59; n = 7) or the recombinant vectors expressing rabies glycoprotein (RG) (0.19 +/- 0.32; n = 8, P = 7 x 10(-6)). The NYVAC vaccine also protected against weight loss, and both the NYVAC and attenuated CDV vaccines protected against the development of some clinical signs of infection, although survival in each of the three vaccine groups was low (one of seven) and not significantly different from the RG controls (none of eight). Combined i.n.-parenteral immunization of ferrets with maternal antibody using NYVAC-HF (n = 9) produced higher titers (1.63 +/- 0. 25) than did i.n. immunization with NYVAC-HF (0.88 +/- 0.36; n = 9) and ALVAC-HF (0.61 +/- 0.43; n = 9, P = 3 x 10(-7)), and survival was also significantly better in the i.n.-parenteral group (3 of 9) than in the other HF-vaccinated animals (none of 18) or in controls immunized with RG (none of 5) (P = 0.0374). Multiple routes were not tested with the ALVAC vaccine. The results suggest that infant ferrets are less responsive to i.n. vaccination than are older ferrets and raises questions about the appropriateness of this route of immunization in infant ferrets or infants of other species.     

Intermediate structures in nuclear morphogenesis following metaphase from HeLaS3 cells can be isolated and temporally grouped

Previously nuclear reformation following metaphase in HeLaS₃ cells was conceptualized in terms of a stepwise process which was continuous throughout anaphase and telophase. This concept was based on a three-dimensional visualization by scanning electron microscopy (SEM) of individual, organically prepared chromatid structures (prenuclei) which could be sequentially arranged. Morphologic analysis revealed unique topographies and morphometric properties which suggested that it should be possible to isolate populations of prenuclei aqueously. Such an isolation using detergents and density centrifugation is presented which yields metaphase plates and two populations of prenuclei with distinctive morphology. Essentially, prenuclei are freed from late mitotic cells in suspension cultures of synchronized HeLaS₃ cells by treatment with 0.1% Nonidet-P40 followed by treatment with a mixture of Tween 40-desoxycholate (0.5%). Critical for the isolation is the presence of a divalent cation (5 mM Mg^{+ +}) and an acid pH (~ 5.8). After density centrifugation, 2N decondensing structures (late intermediates) are recovered from 42% Percoll, and a mixture of 2N predecondensing (early intermediates) and 4N metaphase plates are recovered from 52% Percoll. The latter intermediates can be further separated into highly enriched populations (>94% pure) by fluorescence-activated sorting. Predecondensing structures are of the same overall morphology as prenuclei isolated previously by organic means, can also be ordered sequentially to demonstrate nuclear morphogenesis, and retain centromere/kinetochore loci. These chromosomal loci based on immunostaining of individual structures appear to be positioned centrally during chromatid reassociation and then appear to be dispersed prior to structural rearrangements leading to formation of a disc-like prenucleus. The significance of grouping intermediates temporally and of two protocols of isolation yielding the same structures is discussed with regard to a study of the requirements for nuclear morphogenesis in late mitosis.     

Nuclear reformation following metaphase in HeLa S3 cells: Three-dimensional visualization of chromatid rearrangements

Nuclear reformation from chromatids following metaphase was visualized three-dimensionally for the first time in mammalian cells (HeLa S₃) by scanning electron microscopy (SEM). Anaphase and telophase configurations free of mitotic apparatus, cytoskeletal elements and nuclear envelope were prepared using a slightly modified standard cytological procedure which permitted visualization of chromatid position and orientation. Mid-anaphase alignments were observed to be more complex than previously revealed by light and transmission electron microscopy (TEM). One pole consisted of chromatids joined along their lateral length, the other pole consisted of telomeres, apparently of the longest chromatids, aligned in a double concentric layer. As anaphase progressed, re-association of these chromatids appeared to occur progressively along their lateral length toward their telomeres. Morphological evidence is presented suggesting that this lateral re-association may involve interchromatid fibers. After complete joining, structures resembling a hollow half sphere had formed. Based on different preparative procedures for SEM and published TEM analysis, it is this shell-like configuration upon which the nuclear envelope is reestablished in early telophase. As telophase progressed there was loss in depth of the internal chamber resulting in a disc configuration. Following loss of chromatid outline from the surface of this structure, interphase nuclear shape was assumed. Morphometric determinations revealed relative dimensions of chromatid configurations and supported the conclusion that nuclear reformation proceeded by discrete steps. The complexity of such a process, as revealed by SEM analysis, is discussed.     

1[alpha],25-dihydroxyvitamin D(3) enhances annexin II dependent proliferation of osteoblasts

Cells experience a variety of physiological and non-physiological stresses and consequently have appropriate mechanisms to deal with such deviations from homeostasis. Particularly subject to mechanical stress and shear forces are the cells that make up the bones. Osteoblastic cells can interpret this stress as a stimulus for proliferation; however, the molecular mechanisms underlying this phenomenon are poorly understood. We have identified annexin II as being specifically upregulated in mechanically stressed osteoblasts and found that increased levels of this protein are necessary for 1[alpha],25-dihydroxyvitamin D(3) mediated augmentation of the proliferative response of osteoblasts after mechanical stress. Our data demonstrate a novel interaction between 1[alpha],25-dihydroxyvitamin D(3) and annexin II in the proliferative response of osteoblasts as well as a novel function for annexin II in the stress response. These findings may offer new therapeutic opportunities for conditions that require regenerative osteoblastic activity such as osteoporosis.     

An opposite role is exerted by the acarian Myocoptes musculinus in the outcome of Toxoplasma gondii infection according to the route of the protozoa inoculation

Infection with Toxoplasma gondii leads to a Th1 immune response. Alternatively, the acarian Myocoptes musculinus induces a disease in BALB/c mice that involves Th2 immune mechanisms. In this study, we investigated whether infestation by M. musculinus induces Th2 immune response in C57BL/6 mice and if this response influences the T. gondii-induced Th1 response when mice are inoculated by intraperitoneal or oral route. The animals were infected with M. musculinus and one month later with T. gondii ME-49 strain and the survival and immune response were monitored. The co-infected animals displayed higher mortality rate and the spleen cells showed a decreased IFN-gamma and elevated IL-4 and IL-5 production. These changes were associated with severe pneumonia and wasting condition. On the other hand, when mice were orally infected with 100 T. gondii cysts, co-infection prolonged the survival rates and ameliorated intestinal lesions in association with a significant drop in IFN-gamma levels in sera. These results indicate the interference of Th2 response induced by M. musculinus in a T. gondii-induced Th1 response. Altogether, these data demonstrate the profound interactions between the immune response induced against unrelated organisms T. gondii and M. musculinus, and suggest that this type of interactions may impact clinical disease.