Chlorine oxide in the stratospheric ozone layer: ground-based detection and measurement

Stratospheric chlorine oxide, a significant intermediate product in the catalytic destruction of ozone by atomic chlorine, has been detected and measured by a ground-based 204-gigahertz, millimeter-wave receiver. Data taken at latitude 42 degrees N on 17 days between 10 January and 18 February 1980 yield an average chlorine oxide column density of approximately 1.05 x 10(14) per square centimeter or approximately 2/3 that of the average of eight in situ balloon flight measurements (excluding the anomalously high data of 14 July 1977) made over the past 4 years at 32 degrees N. We find less chlorine oxide below 35 kilometers and a larger vertical gradient than predicted by theoretical models of the stratospheric ozone layer.     

Senescence of nickel-transformed cells by an X chromosome: possible epigenetic control

Transfer of a normal Chinese hamster X chromosome (carried in a mouse A9 donor cell line) to a nickel-transformed Chinese hamster cell line with an Xq chromosome deletion resulted in senescense of these previously immortal cells. At early passages of the A9/CX donor cells, the hamster X chromosome was highly active, inducing senescence in 100% of the colonies obtained after its transfer into the nickel-transformed cells. However, senescence was reduced to 50% when Chinese hamster X chromosomes were transferred from later passage A9 cells. Full senescing activity of the intact hamster X chromosome was restored by treatment of the donor mouse cells with 5-azacytidine, which induced demethylation of DNA. These results suggest that a senescence gene or genes, which may be located on the Chinese hamster X chromosome, can be regulated by DNA methylation, and that escape from senescence and possibly loss of tumor suppressor gene activity can occur by epigenetic mechanisms.     

Pattern of herbage intake rate and bite dimensions of rotationally grazed dairy cows as sward height declines

To allow improved prediction of daily herbage intake of dairy cows in rotational grazing systems, intake behaviour was assessed throughout the day in 24‐h paddocks. Herbage intake in 16 lactating Holstein–Friesian cows was assessed using the short‐term (1‐h) weight gain method at four predetermined natural meal times throughout the day (early morning, T1; late morning, T2; mid‐afternoon, T3; and early evening, T4). The study comprised two 4‐day experiments, each with a cross‐over design of four blocks. In both experiments, cows grazed a 24‐h paddock daily, and the effect of the immediately previous grazing experience on intake behaviour was investigated throughout the day, taking account of daily fluctuations in the short‐term physiological condition of the cows. Experiment 1 was carried out to investigate overall grazing behaviour during meals as a sward is progressively depleted during the day, with intake being assessed within the paddock and, hence, on a depleted sward. Experiment 2 similarly investigated the effect of sward depletion and physiological condition throughout the day on intake, but cows were removed to fresh, undefoliated swards during intake measurement periods; thus, intake rate was not influenced by differences in sward condition. Intake behaviour from both experiments was compared to establish the effect on herbage intake of changes in sward state and non‐sward factors. In Experiment 1, sward surface height, available herbage mass, proportion of leaf and green leaf mass declined as the day progressed. Bite mass declined with sward depletion, and mean intake rate was 1·64 kg dry matter (DM) h^–1, which was significantly lower at T3 (P < 0·01) than during other meals. In Experiment 2, plot sward conditions did not change throughout the day, and intake behaviour also remained constant, with a mean intake rate of 2·11 kg DM h^–1. Mean bite depth as a proportion of pregrazing extended tiller height was constant throughout the day (mean 0·32). The results show that, although cows grazed throughout the day on progressively depleted swards, indicative of rotationally grazed paddocks (Experiment 1), bite mass declined linearly and intake behaviour was variable. However, where intake was assessed on high‐quality, undefoliated swards (Experiment 2), intake behaviour was similar regardless of the time of day and the immediately previous experience. There was some indication of an interaction between the effects of the sward and the physiological condition of the animal on herbage intake.     

Chlorophyll fluorescence of stem cambial tissue reflects dormancy development in Juglans nigra seedlings

Assessment of chlorophyll fluorescence (CF) of forest tree seedlings can provide important insight into physiological function, dormancy status, and stress resistance. This evaluative tool has been measured routinely using foliage on conifer seedlings to assess seedling physiological status during winter dormancy. Absence of foliage during dormancy has thus far precluded the potential application of CF to seedling quality assessment of temperate deciduous hardwood seedlings. Because stems contain chlorophyll, however, assessment of CF using stem tissue may serve as an effective alternative tissue type to facilitate CF measurements. We collected Juglans nigra L. (black walnut) seed from two provenances (Alabama and Indiana, USA) and subjected 1-year-old container seedlings from these provenances to a simulated hardening regime (i.e., progressively decreasing temperatures and photoperiods) in a growth chamber environment over an 18-week period; CF of stem tissue (evaluated as ΦPSII, efficiency of photosystem II) was sampled periodically at seven time intervals. Though both provenance and measurement period significantly affected ΦPSII, measurement period had a much more pronounced effect. Values for ΦPSII fluctuated (ranging from 0.45 to 0.72) during the simulated growth and hardening regimes, generally decreasing over time for both provenances. Our results suggest that physiological status of temperate deciduous seedlings may be effectively evaluated during dormancy by assessing CF of stem tissue.     

Assessment of methoxyfenozide exposure on the sexual attractiveness and responsiveness of adult codling moth, Cydia pomonella L., in small orchard blocks

BACKGROUND: The sexual attractiveness of female and the responsiveness of male codling moth, Cydia pomonella L., exposed to surfaces treated with the ecdysteroid agonist methoxyfenozide were investigated in small orchard block experiments. The main purpose of the study was to determine whether the reported sublethal effects of methoxyfenozide affecting moth behavior also occur under field conditions. RESULTS: Data from the first experiment showed that in some trials untreated females were significantly more attractive to wild males than methoxyfenozide-treated females. The second experiment revealed that some released methoxyfenozide-treated males were not as responsive to calling females as untreated males, and that some untreated females were more attractive to males than methoxyfenozide-treated females. The third experiment revealed that wild males exposed to treated tree surfaces were significantly less responsive to traps than were wild males exposed to untreated trees. However, there were no significant differences in mean recaptures of released males between the untreated and treated orchard blocks. CONCLUSION: Exposure of adult C. pomonella to methoxyfenozide-treated surfaces resulted in a negative impact on male responsiveness to calling females and synthetic pheromone lures. However, the level of impact on the sexual attractiveness of treated females did not appear to be as explicit.     

Variation in pathogen aggressiveness within a metapopulation of the Cakile maritima–Alternaria brassicicola host–pathogen association

Variation in aggressiveness and its consequences for disease epidemiology were studied in the Cakile maritima–Alternaria brassicicola host–pathogen association. Variability in pathogen growth rates and spore production in vitro , as well as disease severity and lesion growth rate on C. maritima in glasshouse inoculation trials, were investigated . Substantial variation was found in growth rates among individual A. brassicicola isolates, as well as among pathogen populations. A significant trade-off also existed between growth and spore production, such that faster-growing isolates produced fewer spores per unit area. While there was little evidence for a link between growth in vitro and either disease severity or lesion development among fast- vs slow-growth isolate classes at the individual isolate level, the results suggest that variation in pathogen fitness components associated with aggressiveness may influence disease dynamics in nature. An analysis using an independent data set of disease prevalence in the associated host populations found a significant positive relationship between the average growth rate of pathogen populations in vitro and disease progress over the growing season in wild host populations. Trade-offs such as those demonstrated between growth rate and spore production may contribute to the maintenance of variation in quantitatively based host–pathogen interactions.     

Report of the American Animal Hospital Association (AAHA) Canine Vaccine Task Force: executive summary and 2003 canine vaccine guidelines and recommendations

The AAHA has undertaken the development of this document in an effort to inform veterinary practitioners, clarify misunderstandings held by veterinarians, and encourage practitioners to recognize that immunization of patients is a medical procedure. As such, it is bound by the same tenets that govern the recommendation of other medical procedures-principally, that it be tailored to the needs of the individual patient. Many diseases we immunize against are ubiquitous. Many are serious and some even life threatening. Some are of limited demographic concern given the exposure risk for each patient. These factors have all been considered in developing the AAHA Canine Vaccination Guidelines. In the end, each veterinarian must do what he or she determines to be in the best interest of the patient. Vaccination of individual animals produces not only individual immunity but also population or herd immunity. Since we have no readily available and reliable way to determine if each patient has developed an adequate immune response, we encourage the practice philosophy of vaccinating more patients while vaccinating each patient no more than needed.     

Moisture content adjustments for dynamic modulus of elasticity of wood members

The influence of moisture content (MC) on the dynamic modulus of elasticity of structural lumber was investigated using transverse vibration testing methods. The flexural rigidity (EI) of a transversely vibrating beam was calculated as the modulus of elasticity (E) multiplied by the moment of inertia (I). The increase in E of lumber due to reduction in moisture content was computed by assuming that the flexural rigidity remains constant with changes in moisture content. Reductions in I due to shrinkage were compensated by the increases in E which led to a proposal for a species-dependent MC adjustment model for modulus of elasticity. The model was validated using 38 mm × 89 mm × 4,290 mm western Canadian Spruce–Pine–Fir dimension lumber evaluated in the “as-received” and “dry” conditions. Results obtained from the species-dependent model agreed closely with those from the E adjustment equation for dimension lumber given in ASTM D 1990. The results show that the ASTM moisture adjustment procedures can be used to adjust dynamic E values for changes in moisture content also.     

Where art thou louse? A snapshot of attachment location preferences in salmon lice on Atlantic salmon hosts in sea cages

Problematic sea lice infestations on farmed Atlantic salmon (Salmo salar) have motivated extensive research and development into new methods to prevent, monitor and control sea lice. Most of these technologies require detailed information on the behaviour, spatial distribution and demography of lice on host fish. This study investigated how salmon lice (Lepeophtheirus salmonis) infestation density varies across the host's surface under sea cage farming conditions. Lice abundance, demography and attachment location were tracked over time, with repeated sampling of 300 individually tagged salmon across three replicate experimental sea cages. The data reveal clear differences in attachment locations according to sex and stage, but with an overall preference for the dorsal surface among mobile stages—dorsal head for adult females and dorsal-posterior section for males and pre-adults. Total lice abundance was highly variable between repeated measures of individual fish, consistent with frequent host-switching or mortality. Total lice numbers also declined between sampling dates, likely due to handling, with lost mobile lice being almost exclusively adult males. As the distribution of sea lice on hosts is likely determined by numerous factors, future image-based automated detection systems should be validated in settings that reflect the complex host–parasite interactions that occur in open farming systems.