Photoinhibition of photosystem II in tobacco plants overexpressing glutathione reductase and poplars overexpressing superoxide dismutase

We studied photoinhibition in two cultivars of tobacco ( Nicotiana tabacum L.) expressing the bacterial gor gene in the cytosol and in four lines of poplar ( Populus tremula × P. alba ) expressing the FeSOD gene of Arabidopsis thaliana in the chloroplast. The respective total activities of glutathione reductase (EC 1.6.4.2) in leaves of gor tobaccos and superoxide dismutase (EC 1.15.1.1) in the FeSOD poplars were 5–8 times higher than in the respective untransformed control plants. Leaves of control and transformed plants were subjected to high-light stress at 20°C, and photoinhibition of photosystem II (PSII) was measured by oxygen evolution and chlorophyll fluorescence. The leaves were illuminated both in the presence and absence of lincomycin, which inhibits chloroplast protein synthesis. In both cases, the time course of loss of PSII activity was identical in plants overproducing superoxide dismutase (SOD) and in the untransformed controls, suggesting that the ability to convert superoxide to hydrogen peroxide is not a limiting factor in protection against photoinhibition, or in the repair of photoinhibitory damage or that the site of O₂⁻ production is not accessible to the transgene product. The rate constant of photoinhibition, measured in lincomycin-treated leaves, was smaller in glutathione reductase (GR) overproducing tobacco cv. Samsun than in the respective wild-type, but this difference was not seen in cv. Bel W3. The steady-state level of PSII activity measured when the PSII repair cycle was allowed to equilibrate with photoinhibitory damage under high light was not higher in the GR overproducing cv. Samsun, suggesting that the repair of photoinhibitory damage was not enhanced in plants overproducing GR in the cytosol.     

Monosaccharide Sequence of Protein-Bound Glycans of Uukuniemi Virus

Uukuniemi virus, a member of the Bunyaviridae family, was grown in BHK-21 cells in the presence of [³H]mannose. The purified virions were disrupted with sodium dodecyl sulfate and digested with pronase. The [³H]mannose-labeled glycopeptides of the mixture of the two envelope glycoproteins G1 and G2 were characterized by degrading the glycans with specific exo-and endoglycosidases, by chemical methods, and by analyzing the products with lectin affinity and gel chromatography. The glycopeptides of Uukuniemi virus fell into three categories: complex, high-mannose type, and intermediate. The complex glycopeptides probably contained mainly two NeuNAc-Gal-GlcNAc branches attached to a core (Man)₃(GlcNAc)₂ peptide. The high-mannose-type glycans were estimated to contain at least five mannose units attached to two N-acetylglucosamine residues. Both glycan species appeared to be similar to the asparagine-linked oligosaccharides found in many soluble and membrane glycoproteins. The results suggested that the intermediate glycopeptides contained a mannosyl core. In about half of the molecules, one branch appeared to be terminated in mannose, and one appeared to be terminated in N-acetylglucosamine. Such glycans are a novel finding in viral membrane proteins. They may represent intermediate species in the biosynthetic pathway from high-mannose-type to complex glycans. Their accumulation could be connected with the site of maturation of the members of the Bunyaviridae family. Electron microscopic data suggest that the virions bud into smooth-surfaced cisternae in the Golgi region. The relative amounts of [³H]mannose in the complex, high-mannose-type, and intermediate glycans were 25, 62, and 13%, respectively, which corresponded to the approximate relative number of oligosaccharide chains of 2:2.8:1, respectively, in the roughly equimolar mixture of G1 and G2. Endoglycosidase H digestion of isolated [³⁵S]methionine-labeled G1 and G2 proteins suggested that most of the complex and intermediate chains were attached to G1 and that most of the high-mannose-type chains were attached to G2.     

Determination of aldosterone in serum by liquid chromatography-tandem mass spectrometry

Measurement of serum aldosterone is clinically important in the diagnosis of hypertension. While isotope dilution gas chromatography-mass spectrometry (ID-GC-MS) provides reliable results, it requires derivatization and is lengthy and time-consuming. Detection by liquid chromatography-mass spectrometry (LC-MS) is a potentially superior method. The analysis utilizes 0.5mL of serum. The samples were extracted with dichloromethane-ether. The extract was evaporated to dryness and aldosterone was analyzed by LC-MS/MS operating in the negative mode ESI after separation on a reversed-phase column. Aldosterone was also measured by RIA. The calibration curves for analysis of serum aldosterone exhibited consistent linearity and reproducibility in the range of 60-3000pmol/L. Interassay CVs were 4.3-7.5% at aldosterone concentrations of 97-993pmol/L. The lower limit of quantitation (LOQ) was 30pmol/L (signal to noise ratio=10). The mean recovery of the analyte added to serum ranged from 95 to 102%. The regression equation by LC-MS/MS (x) and RIA (y) method was: y=1.33x+185 (r=0.95; n=124). Sensitivity and specificity of the LC-MS/MS method for serum aldosterone offer advantages over GC-MS by eliminating derivatization. The novel method is rapid, reliable and simple to perform with a routine LC-MS/MS spectrometer. The sensitivity is adequate for patient samples. Aldosterone concentrations reported by nonextraction RIA were consistently higher than those produced by LC-MS/MS.     

Hantavirus infections in fluctuating host populations: the role of maternal antibodies

Infected females may transfer maternal antibodies (MatAbs) to their offspring, which may then be transiently protected against infections the mother has encountered. However, the role of maternal protection in infectious disease dynamics in wildlife has largely been neglected. Here, we investigate the effects of Puumala hantavirus (PUUV)-specific MatAbs on PUUV dynamics, using 7 years'' data from a cyclic bank vole population in Finland. For the first time to our knowledge, we partition seropositivity data from a natural population into separate dynamic patterns for MatAbs and infection. The likelihood of young of the year carrying PUUV-specific MatAbs during the breeding season correlated positively with infection prevalence in the overwintered parent population in the preceding spring. The probability of PUUV infection varied between seasons (highest in spring, lowest in late summer) and depended on population structure, but was also, in late autumn, notably, negatively related to summer MatAb prevalence, as well as to infection prevalence earlier in the breeding season. Hence, our results suggest that high infection prevalence in the early breeding season leads to a high proportion of transiently immune young individuals, which causes delays in transmission. This suggests, in turn, that MatAb protection has the potential to affect infection dynamics in natural populations.     

Resource matching and population dynamics in a two-patch system

We study resource matching – the relationship between resource supply and forager numbers – under conditions of fluctuating population dynamics in a two-patch system. For the inter-patch dispersal we apply the patch-departure rule following the principle of the ideal free distribution: leave the current patch of residence if local conditions are worse than conditions elsewhere on average. We show that such a dispersal rule synchronises cyclic and chaotic local population dynamics, but unlike many other dispersal rules, leaves the underlying population dynamics untouched. We also show that the IFD dispersal rule is not very sensitive to biased information and navigation failures during the dispersal phase. Even under such circumstances we observe a quick process of populations becoming synchronised, even when the population dynamics are chaotic. We conclude that an IFD patch-departure rule represents an ESS dispersal behaviour towards which the dispersal patterns should evolve.     

Egg shell quality,clutch size and hatching success of the great tit (Parus major) and the pied flycatcher (Ficedula hypoleuca) in an air pollution gradient

Egg shell thickness, egg volume, clutch size and hatching success of Parus major and Ficedula hypoleuca were studied at 14 study sites around a copper smelter complex in Harjavalta, south-west Finland, in 1991–1993. In 1991–1992 unhatched eggs were collected to measure shell quality. F. hypoleuca was more susceptible to pollutants than P. major, the response of which was weaker in all aspects studied. Egg shells of F. hypoleuca were about 17% thinner and eggs were about 8% smaller in volume near the factory than at a distance of 10 km. The clutch size of F. hypoleuca was significantly smaller and hatching success markedly lower at a study site next to the factory complex than at all other sites. In P. major, variation in shell thickness and egg volume was not significantly related to the distance from the pollution source. Clutch size and hatching success of P. major did not significantly differ among study sites, although the trend in hatching success was in the same direction as in F. hypoleuca. Clutches of both species contained less shell material and both species had more nests without eggs near the factory than further away. The surface structure of the eggshells was studied by scanning electron microscope. Especially in F. hypoleuca, the egg shell surface was more rough and porous near the factory. The roles of Ca and heavy metals in shell thinning are discussed.     

Life in varying environments: experimental evidence for delayed effects of juvenile environment on adult life history

1.?The effects of environment experienced during early development on phenotype as an adult has started to gain vast amounts of interest in various taxa. Some evidence on long-term effects of juvenile environment is available, but replicated experimental studies in wild animals are still lacking. 2.?Here we report the first replicated experiment in wild mammals which examines the long-term effects of juvenile and adult environments on individual fitness (reproduction, survival and health). The early development of bank vole (Myodes glareolus) individuals took place in either food-supplemented or un-supplemented outdoor enclosures. After the summer, adult individuals were reciprocally changed to either a similar or opposite resource environment to overwinter. 3.?Adult environment had an overriding effect on reproductive success of females so that females overwintering in food-supplemented enclosures had a higher probability of breeding and advanced the initiation of breeding. However, the characteristics of their litters were determined by juvenile environment: females initially grown in food-supplemented conditions subsequently produced larger litters with bigger pups and a male-biased sex ratio. 4.?In males, individuals growing in un-supplemented conditions had the highest survival irrespective of adult environment during winter, whereas in females, neither the juvenile nor adult environments affected their survival significantly. The physiological condition of voles in spring, as determined by haematological parameters, was also differentially affected by juvenile (plasma proteins and male testosterone) and adult (haematocrit) environments. 5.?Our results suggest that (i) life-history trajectories of voles are not strictly specialized to a certain environment and (ii) the plastic life-history responses to present conditions can actually be caused by delayed effects of the juvenile environment. More generally, the results are important for understanding the mechanisms of delayed life-history effects as well as recognizing their population dynamic consequences.     

Sexual antagonism for testosterone maintains multiple mating behaviour

1. The persistence of multiple mating remains one of the fundamental questions in evolutionary biology. In theory, multiple mating is predicted to improve female fitness cumulatively through direct and/or genetic benefits. However, intra-locus sexual conflicts may potentially constrain or even eliminate these benefits owing to the gender load imposed by sexually antagonistic selection. 2. Here, we tested whether sexually antagonistic selection can maintain the variance in multiple mating behaviour of bank voles (Myodes glareolus) by manipulating the hormone testosterone through artificial selection in the laboratory. Among mammals, testosterone is a sexually dimorphic fitness-related trait under selection and is known to affect mating behaviour. We conducted mating trials in which females derived from family-based selection of testosterone were sequentially paired with four males of different testosterone profiles. 3. We show that artificial selection for high testosterone increased the mating rate of males, but clearly decreased the number of partners that females mated with (and vice versa). Because multiple mating was beneficial for the reproductive success of both sexes, as evidenced by the positive Bateman gradients, the divergent evolutionary interests of testosterone between the sexes can maintain this polygynandrous mating system. 4. Our results highlight how mating rate is concordantly selected in both sexes; however, it is largely influenced by testosterone, which is under sexually antagonistic selection. 5. This study is the first one to emphasise the direct and indirect effects of the endocrine system not only on reproductive physiology and behaviour but also for the evolution of genetic mating strategies in mammals.