Diameter growth: can live trees decrease?

Growth refers to an increase in dimensions with time and isimplicit in the expected continual increase in tree dimensions.Tree diameters, however, could decrease during the growing seasondue to water depletion. Annual negative growth measurementsare usually attributed to human error and not to other physiologicalor physical processes. Although seasonal and diurnal fluctuationsof diameter have been well documented, perennial decrement ofdiameter has not been the focus of physiological research. Theaim of this work was to analyse the potential causes of decreasein annual diameter growth related to tree mortality due to self-thinningin Nothofagus pumilio forests and to quantify the variationsin water depletion of the tree trunks. Some trees did presentnegative annual diameter increments associated with a watercontent decrease in the trunks (77 per cent in live trees comparedwith 56 per cent in recently dead individuals), which produceda contraction (more than 8 per cent of the initial diameter)in the wood and the bark. Trees could survive during 2–5growth seasons with continual decreases in their diameters (14per cent, standard error 5 per cent of the trees in the studiedstand) until the water content reached a limit where mortalityresulted. Therefore, the occurrence of data showing a diameterdecrease in successive forest inventories may be due to physiologicaland physical processes in the natural dynamics of the stand,and not exclusively be explained away as the results of humanmeasurement errors.     

The dwarfing mechanism of citrus rootstocks F&A 418 and #23 is related to competition between vegetative and reproductive growth

The annual development of Navelina (Citrus sinensis (L.) Osbeck) trees budded on three hybrid citrus rootstocks was studied. Two rootstocks, named #23 and #24, were obtained from the cross of Troyer citrange (C. sinensis x Poncirus trifoliata (L.) Raf.) x Cleopatra mandarin (C. reshni Hort. ex Tan.). The third rootstock, named F&A 418, came from a cross of Troyer citrange x common mandarin (C. deliciosa Ten.). Rootstocks #23 and F&A 418 are dwarfing rootstocks and reduce the size of the scion by about 75%. Rootstock #24 yields a standard size scion. Major growth differences that influenced tree size were apparent during the first summer after grafting and appeared to be related to fruit productivity, because defruiting the dwarfed scions caused a significant increase in vegetative shoot development, including summer sprouting. The reduced growth of the dwarfed scions was not restored by hormone application, indicating that a hormonal deficiency is unlikely to be the primary reason for scion dwarfing, although differences in gibberellin concentrations were found in actively growing shoots. Leaf photosynthesis was similar in scions on all three rootstocks, but the carbohydrate accumulation in fruits and fibrous roots during the summer sprouting period was significantly greater in the dwarfed trees than in the standard trees. Our results suggest that the dwarfing mechanism induced by the F&A 418 and #23 rootstocks is mediated by enhanced reproductive development and fruit growth, resulting in reduced vegetative development in the summer. Thus, a change in the pattern of assimilate distribution appears to be one of the main components of the dwarfing mechanism.     

Protein changes in the albedo of citrus fruits on postharvesting storage

In this work, major protein changes in the albedo of the fruit peel of Murcott tangor (tangerine x sweet orange) during postharvest ageing were studied through 2D PAGE. Protein content in matured on-tree fruits and in fruits stored in nonstressing [99% relative humidity (RH) and 25 degrees C], cold (99% RH and 4 degrees C), and drought (60% RH and 25 degrees C) conditions was initially determined. Protein identification through MS/MS determinations revealed in all samples analyzed the occurrence of manganese superoxide dismutase (Mn SOD), actin, ATP synthase beta subunit (ATPase), citrus salt-stress associated protein (CitSap), ascorbate peroxidase (APX), translationally controlled tumor protein (TCTP), and a cysteine proteinase (CP) of the papain family. The latter protein was identified in two different gel spots, with different molecular mass, suggesting the simultaneous presence of the proteinase precursor and its active form. While Mn SOD, actin, ATPase, and CitSap were unchanged in the assayed conditions, TCTP and APX were downregulated during the postharvest ageing process. Ageing-induced APX repression was also reversed by drought. CP contents in albedo, which were similar in on- and off-tree fruits, were strongly dependent upon cold storage. The active/total CP protein ratio significantly increased after cold exposure. This proteomic survey indicates that major changes in protein content in the albedo of the peel of postharvest stored citrus fruits are apparently related to the activation of programmed cell death (PCD).     

Ecological preferences of exophilic and endophilic ticks (Acari: Ixodidae) parasitizing wild carnivores in the Iberian Peninsula

Ticks parasitizing wild carnivores and the tick-borne pathogens (TBPs) that they transmit may affect domestic carnivores and humans. Thus, investigating the role of wild carnivores as tick hosts is of relevance for understanding the life cycle of ticks in natural foci and the epidemiology of TBPs shared with domestic animals and humans. Therefore, the main objective of this study was to determine the ixodid tick fauna of wild carnivores in Peninsular Spain and the environmental factors driving the risk of wild carnivores to be parasitized by ixodid ticks. We hypothesized that the adaptation of tick species to differing climatic conditions may be reflected in a similar parasitization risk of wild carnivores by ticks between bioclimatic regions in our study area. To test this, we surveyed ixodid ticks in wild carnivores in oceanic, continental-Mediterranean, and thermo-Mediterranean bioclimatic regions of Peninsular Spain. We analyzed the influence of environmental factors on the risk of wild carnivores to be parasitized by ticks by performing logistic regression models. Models were separately performed for exophilic and endophilic ticks under the expected differing influence of environmental conditions on their life cycle. We found differences in the composition of the tick community parasitizing wild carnivores from different bioclimatic regions. Modelling results partially confirmed our null hypothesis because bioclimatic region was not a relevant factor influencing the risk of wild carnivores to be parasitized by exophilic ticks. Bioclimatic region was however a factor driving the risk of wild carnivores to be parasitized by endophilic ticks. Spanish wild carnivores are hosts to a relevant number of tick species, some of them being potential vectors of pathogens causing serious animal and human diseases. Information provided herein can be of help to understand tick ecology in Spanish wildlife, the epidemiology of tick-borne diseases, and to prevent the risks of TBPs for wildlife, domestic animals, and humans.     

EcPV2 DNA in equine genital squamous cell carcinomas and normal genital mucosa

Squamous cell carcinoma (SCC) represents the most common genital malignant tumor in horses. Similar to humans, papillomaviruses (PVs) have been proposed as etiological agents and recently Equine papillomavirus type 2 (EcPV2) has been identified in a subset of genital SCCs. The goals of this study were (1) to determine the prevalence of EcPV2 DNA in tissue samples from equine genital SCCs, penile intraepithelial neoplasia (PIN) and penile papillomas, using EcPV2-specific PCR, (2) to examine the prevalence of latent EcPV2 infection in healthy genital mucosa and (3) to determine genetic variability within EcPV2 and to disentangle phylogenetic relationships of EcPV2 among PVs. EcPV2 DNA was detected in all but one penile SCC (15/16), in all PIN lesions (8/8) and penile papillomas (4/4). Additionally, EcPV2 DNA was demonstrated in one of two metastasized lymph nodes, one contact metastasis in the mouth, two vaginal and one anal lesion. In healthy horses, EcPV2 DNA was detected in 10% (4/39) of penile swabs but in none of vulvovaginal swabs (0/20). This study confirms the presence of EcPV2 DNA in equine genital SCCs and shows its involvement in anal lesions, a lymph node and contact metastases. Latent EcPV2 presence was also shown in normal male genital mucosa. We found that different EcPV2 variants cocirculate among horses and that EcPV2 is related to the Delta+Zeta PVs and is only a very distant relative of high-risk human PVs causing genital cancer. Thus, similar viral tropism and similar malignant outcome of the infection do not imply close evolutionary relationship.     

MM3-ELISA evaluation of coproantigen release and serum antibody production in sheep experimentally infected with Fasciola hepatica and F. gigantica

During an experimental infection of sheep with Fasciola hepatica or F. gigantica, MM3-SERO and MM3-COPRO ELISA tests were applied to compare the kinetics of antibody production and coproantigen release between the 2nd and 32nd week post-infection (wpi). The Kato-Katz technique was used to measure the kinetics of egg shedding by both Fasciola species (eggs per gram of feces, epg). The kinetics of IgG antibodies for all sheep infected with F. hepatica and F. gigantica followed a similar pattern. Optical density (OD) increased rapidly between the 4th until the 12th wpi, when the highest values were reached and then decreased slowly until the 32nd wpi. Coproantigen levels increased above the cut-off value between 6 and 9 wpi in the F. hepatica group, and between 9 and 11 wpi in the F. gigantica group. The comparison between coproantigen levels and epg indicated that F. hepatica-infected sheep had detectable amounts of coproantigens 4–7 weeks before patency (egg shedding), while F. gigantica-infected sheep had detectable amounts of coproantigens 3–6 weeks before patency. When comparing the kinetics of coproantigen release vs the kinetics of epg, a similar pattern emerged, but with a two-week time-lag in epg, for both F. hepatica and F. gigantica infections. The amount of coproantigen release by each adult was not burden dependent for F. hepatica infection (burden of 33–66 adults), while it was for F. gigantica infection (burden of 17–69 adults). The results demonstrate the usefulness of the MM3-SERO and MM3-COPRO ELISAs as tools for the diagnosis of early as well as long-term fascioliasis infections, and suggest that they can potentially be applied to human fascioliasis even in countries where F. hepatica and F. gigantica co-exist. These tests can be employed not only in the diagnosis, but also in studies on epidemiology as well as pathogenesis and treatment in animals and humans since they allow post-treatment infection monitoring.     

Analgesic and motor-blocking action of epidurally administered levobupivacaine or bupivacaine in the conscious dog

Objective  To compare the analgesic and motor-blocking effects of epidurally administered levobupivacaine and bupivacaine in the conscious dog.
Study design  Prospective, randomized, cross-over study.
Animals  Six adult female Beagle dogs.
Methods  Each animal received three doses of levobupivacaine or bupivacaine (0.5, 1.0 and 1.5 mg kg⁻¹; concentrations 0.25%, 0.50%, and 0.75%, respectively) in a total volume of 0.2 mL kg⁻¹ by means of a chronically implanted epidural catheter. Onset, duration (through pinch response in the sacral, lumbar and toe areas) and degree of analgesia and motor-blocking status was determined with a scoring system and at regular intervals over 8.5 hours before (baseline) and after drug administration.
Results  Epidurally administered levobupivacaine and bupivacaine had a similar dose-dependent analgesic action with no significant differences in onset (range: 5–8 minutes), duration (bupivacaine: 42 ± 28, 135 ± 68 and 265 ± 68 minutes, and levobupivacaine: 28 ± 33, 79 ± 55 and 292 ± 133 minutes; 0.25%, 0.50%, and 0.75%, respectively) or maximum degree of analgesia. However, levobupivacaine tended to produce a shorter duration of motor block than bupivacaine and the difference in the motor to nociceptive blockade times was significant at the highest dose.
Conclusion  Epidural levobupivacaine produced an analgesic action similar to that of bupivacaine.
Clinical relevance  Epidural levobupivacaine is suitable for clinical use in dogs, mostly at the highest dose if a high degree of analgesia is required.