bluuebunny/crossref_metadata_2025_split huggingface dataset:
Genetic and management factors that influence the susceptibility of cattle toMycobacterium bovisinfection
Authors: Phillips Clive J. C. , Foster Charles R. W. , Morris Pat A. , Teverson Rachel 
Published: February 2003

AbstractGenetic variation in the susceptibility of cattle toMycobacterium bovisinfection exists in differences between families and species, but not breeds. Susceptibility toM. bovisinfection increases with age of cattle. Natural exposure toM. bovisor environmental mycobacteria may assist in the development of specific immunity, but there is no direct evidence for such immunological priming of tuberculosis resistance in cattle. This has, however, been demonstrated in humans and other animals. Since non-specific mechanisms have a role in protective immunity, developing an effective vaccine will be difficult, even though some protection of other species has been achieved. Immunological suppression in the periparturient period can produce anergic reactors, which may act as a constant source of infection for cattle-to-cattle transmission. Circumstantial evidence suggests that an adequate intake of mineral, vitamin and protein reduces the susceptibility of cattle. Although weather patterns have been implicated in the susceptibility of herds toM. bovisinfection, there is insufficient information to determine the risk factors precisely. It is concluded that some reduction in the susceptibility of cattle toM. bovisinfection can be achieved by modifications to the management system to minimize risk factors, but that a considerable amount of further research is required.
Transfer of energy substrates across the ruminal epithelium: implications and limitations
Authors: Gäbel G. , Aschenbach J. R. , Müller F. 
Published: February 2003

AbstractThe ruminal epithelium has an enormous capacity for the absorption of short-chain fatty acids (SCFAs). This not only delivers metabolic energy to the animal but is also an essential regulatory mechanism that stabilizes the intraruminal milieu. The epithelium itself, however, is endangered by the influx of SCFAs because the intracellular pH (pHi) may drop to a lethal level. To prevent severe cytosolic acidosis, the ruminal epithelium is able to extrude (or buffer) protons by various mechanisms: (i) a Na+/H+exchanger, (ii) a bicarbonate importing system and (iii) an H+/monocarboxylate cotransporter (MCT). Besides pHiregulation, the MCT also provides the animal with ketone bodies derived from the intraepithelial breakdown of SCFAs. Ketone bodies, in turn, can serve as an energy source for extrahepatic tissues. In addition to SCFA uptake, glucose absorption has recently been identified as a potential way of eliminating acidogenic substrates from the rumen. At least with respect to SCFAs, absorption rates can be elevated when adapting animals to energy-rich diets. Although they are very effective under physiological conditions, the absorptive and regulatory mechanisms of the ruminal epithelium also have their limits. An increased number of protons during the state of ruminal acidosis can be eliminated neither from the lumen nor the cytosol, thus worsening dysfermentation and finally leading to functional and morphological alterations of the epithelial lining.
Empirical and theoretical evidence for herd size as a risk factor for swine diseases
Authors: Gardner Ian A. , Willeberg Preben , Mousing Jan 
Published: February 2003

AbstractHerd size is frequently studied as a risk factor for swine diseases, yet the biological rationale for a reported association with herd size (whether positive or negative) is rarely adequately discussed in published epidemiological studies. Biologically plausible reasons for a positive association between herd size and disease include a greater risk of introduction of pathogens from outside the herd, greater risk of transmission of pathogens within and among herds when the herd is large, and effects of management and environmental factors that are related to herd size. However, compared with owners of small herds, owners of large herds might more frequently adopt management and housing practices that mitigate this theoretically increased risk. We used studies of pleuritis, pneumonia and pseudorabies to describe the epidemiological issues involved in evaluations of the relationship between management factors, herd size and disease. In future studies, we recommend that (i) herd size be measured in a way that best characterizes the true population at risk; (ii) studies that evaluate management-related risk factors should account for herd size wherever possible; (iii) population-based studies of the interrelationships among management factors and between management factors, herd size, herd density and pig density be done; (iv) likely biological reasons for any herd-size effect be postulated; and (v) the distribution of herd sizes in the source population and the study sample be described.
Carbon stocks in Indonesian homegarden systems: Can smallholder systems be targeted for increased carbon storage?
Authors: Roshetko James M. , Delaney Matt , Hairiah Kurniatun , Purnomosidhi Pratiknyo 
Published: February 2003

AbstractHomegardens are a common smallholder agroforestry system in Indonesia and throughout the tropics. These speciesrich, tree-based systems produce non-wood and wood products for both home use and market sale. Due to their high biomass, these systems simultaneously offer potential for carbon (C) storage. While small size limits the amount of C stored by individual smallholder agroforestry systems, on a per area basis these systems can store as much C as some secondary forests. In aggregate, smallholder homegarden agroforestry systems can contribute significantly to a region's carbon budget while simultaneously enhancing smallholder livelihoods. A field study in Lampung, Indonesia indicates that homegardens with an average age of 13 years store 35.3 Mg C ha−1 in their above-ground biomass, which is on par with the C stocks reported for similar-aged secondary forests in the same area. However, to compare accurately the C stocks of different land-use systems a scale is required that adjusts C stocks of the systems' ages and rotation lengths to a common base. The time-averaged C stock, which is half the C stock at the maximum rotation length, serves this purpose. Our projections reveal that, depending on management options, the time-averaged above-ground C stocks of homegarden systems could vary from 30 to 123 Mg C ha−1. These projected timeaveraged above-ground C stocks of homegardens are substantially higher than those of Imperata-cassava systems (2.2 Mg C ha−1), which is an extensive vegetation type in the study area. If homegarden systems and other smallholder tree-based systems were to expand in currently degraded and underutilized lands, such as Imperata grasslands, the C sequestration potential would be about 80 Mg C ha−1, with considerable variation depending on species composition and management practices. Clear opportunity exists to induce management that leads to higher C stocks at the systems level. However, incentive mechanisms are needed that assure smallholders will benefit from selecting management practices that favor higher C stocks.
Incentives for reforestation of agricultural land: What will a market for carbon sequestration credits contribute?
Authors: Shabman Leonard , Zepp Laura , Wainger Lisa , King Dennis 
Published: February 2003

AbstractReforestation of frequently flooded, marginally productive agricultural lands may provide environmental benefits. However, for reforestation to occur private landowners must earn enough revenues from forestlands to offset both the costs of reforesting as well as any forgone agricultural income. Among the possible revenue sources is the sale of carbon sequestration credits earned from reforestation. We simulate the financial feasibility of reforestation and the contribution of carbon sequestration credit sales to the net income possible from reforestation in a case study area of frequently flooded soybean fields in the Mississippi Alluvial Plain (the Delta). Under current market conditions, reforestation appears to be financially feasible on only the most marginally productive agricultural lands. Markets for carbon credits may contribute to positive financial returns of reforestation, but other policies and market opportunities will be necessary for a positive return to be realized.
Carbon offsets for conservation and development in Indonesia?
Authors: Tomich Thomas P. , de Foresta Hubert , Dennis Rona , Ketterings Quirine , Murdiyarso Daniel , Palm Cheryl , Stolle Fred , Suyanto  , van Noordwijk Meine 
Published: February 2003

AbstractThe logic of the Clean Development Mechanism (CDM) and other such ‘carbon (C) offsets’ rests on the notion that the opportunity cost of reducing C emissions is lower in developing countries, creating opportunities for mutually beneficial C trading. While the CDM may offer significant gross financial benefits, there has been little analysis of the opportunity costs of foregone resource exploitation and development opportunities. In addition to assessing the potential for net benefits, this paper also considers the practical implications for design and implementation of C offsets for forest conservation and agroforestation in Indonesia. Virtually nothing is known about these administrative factors, and their associated costs, which can also play a decisive role in feasibility of C offset schemes. Data are from field studies in the lowlands of the Indonesian island of Sumatra, where forests and derived land uses are broadly representative of the lowland humid tropical rainforest systems of insular South-East Asia. These data are the basis for assessing the trade-offs between natural forest protection for C sequestration and conversion to other land uses to meet national development objectives that directly affect people's livelihoods. Carbon stocks are analyzed in terms of ‘time-averaged’ C, an indicator developed for this project. Opportunity costs of land-use alternatives are estimated using standard techniques for economic assessment of investment projects in developing countries. The study finds that imputed timber values are a significant share of the opportunity costs of forest conservation, even for conservative estimates of timber prices. The question of compensating for these foregone values raises complex questions regarding the political economy of Indonesia, since property rights over these resources are highly contentious. These controversies over property rights are also examined within the context of recurrent smoke pollution from land fires in Indonesia, that (among other problems) contribute to greenhouse gas emissions. This smoke is symptomatic of deeper political and institutional problems that raise questions about the permanence of C storage through land-use practices in Indonesia. In comparison to forest conservation, C offsets through agroforestation seem more feasible in Indonesia because property rights over timber from planted trees would be easier to establish and enforce than property rights over timber from natural forests. Although results in this paper look promising, there is still much to be learned about implementation costs, even for the ‘easier’ case of agroforestation.
Life cycle variation of Myzus persicae (Hemiptera: Aphididae) in Greece
Authors: Margaritopoulos J.T. , Tsitsipis J.A. , Goudoudaki S. , Blackman R.L. 
Published: February 2003

AbstractDuring the years 1995–1999 the life cycle category of 2797 clones of Myzus persicae (Sulzer) was examined. The clones originated from primary and secondary hosts from different localities of North and Central Greece and the island of Crete in the south. Four different overwintering life cycle strategies were found that have also been described for M. persicae and other heteroecious species previously. A geographical variation was found in the proportion of holocyclic clones from tobacco and other secondary hosts associated with the abundance of the primary host in the sampling regions. In Central Macedonia, around the main peach-growing regions, the proportion of holocyclic clones was mostly above 50% and in some cases reached 100%. In localities of East Macedonia, holocyclic clones were also frequent. On the other hand, further south or in north-eastern Greece, where peach is not common, the proportion of holocyclic clones varied between 0 and 33%. Fifty seven percent of examined anholocyclic clones produced males under short day conditions, suggesting that androcyclic clones in Greece represent an important factor of genetic variability. Intermediate clones were sampled from all host-plants but at low frequencies (3.6% of total examined clones and 6.9% of non-holocyclic ones). Moreover, a regional variation was found in different colour forms feeding on tobacco plants. Red clones were predominant in regions where aphids overwinter parthenogenetically on weeds or winter crops. However, almost all clones from the primary host were green. The ecological aspects of life cycle variation are discussed.
PCR–RFLP identification of endemic Chilean species of Rhagoletis (Diptera: Tephritidae) attacking Solanaceae
Authors: Salazar M. , Theoduloz C. , Vega A. , Poblete F. , González E. , Badilla R. , Meza-Basso L. 
Published: February 2003

AbstractFour species of the genus Rhagoletis are native to Chile: R. nova (Schiner), R. conversa, (Brèthes), R. penela Foote and R. tomatis Foote. Currently, identification of these species is based on morphological criteria, but their strong similarity makes precise recognition difficult. To clarify species separation for quarantine purposes, a reliable method based on a PCR–RFLP procedure is reported. A DNA region containing mitochondrial NADH dehydrogenase genes was selected as a target sequence for the analysis. The amplification products (c. 1 kb) were digested with either SspI or DdeI, yielding specific patterns that differentiated each of the endemic species. Complete nucleotide sequences were determined, confirming empirical restriction maps. This report updates information on the geographical distribution of Rhagoletis species in Chile.
Developmental and reproductive biology ofScirtothrips perseae(Thysanoptera: Thripidae): a new avocado pest in California
Authors: Hoddle M.S. 
Published: February 2003

AbstractThe developmental and reproductive biology of a new avocado pest,Scirtothrips perseaeNakahara, was determined in the laboratory at five constant temperatures, 15, 20, 25, 27.5 and 30°C. At 20°C,S. perseaeexhibited greatest larval to adult survivorship (41%), and mated females produced a greater proportion of female offspring at this temperature when compared to 15, 25, 27.5 and 30°C. Average lifetime fecundity and preoviposition period was greatest at 15°C at 39.6 eggs per female and 17.6 days, respectively. Jackknifed estimates of net reproduction (Ro), capacity for increase (rc), intrinsic rate of increase (rm), and finite rate of increase (λ) were all significantly greater at 20°C than corresponding values at 15, 25 and 27.5°C. Population doubling time (Td) was significantly lower at 20°C, indicatingS. perseaepopulations can double 33–71% faster at this temperature in comparison to 15, 25 and 27.5°C. Mean adult longevity decreased with increasing temperature, from a maximum of 52.4 days at 15°C to a minimum of 2.4 days at 30°C. Developmental rates increased linearly with increasing temperatures for eggs and rates were non-linear for development of first and second instar larvae, propupae, pupae, and for egg to adult development. Linear regression and fitting of the modified Logan model to developmental rate data for egg to adult development estimated that 344.8 day degrees were required above a minimum threshold of 6.9°C to complete development. An upper developmental threshold was estimated at 37.6°C with an optimal temperature of 30.5°C for egg to adult development. Unmated females produced only male offspring confirming arrhenotoky inS. perseae.
The chemical characterization of the epicuticular hydrocarbons of Aedes aegypti (Diptera: Culicidae)
Authors: Horne G.L. , Priestman A.A. 
Published: February 2003

AbstractThe chemical characterization of the hydrocarbon fraction of the epicuticular lipids of the vector mosquito Aedes aegypti (Linnaeus) was performed using gas chromatography (GC) and gas chromatography–electron impact mass spectrometry (GC–MS). Seventy eight compounds were detected in purified hexane extracts and of these, 42 hydrocarbons were identified and several of the remaining compounds were partially characterized. The hydrocarbon classes present were n-alkanes, monomethylalkanes, dimethylalkanes and alkenes and the results were similar to those published for other Aedes species. Quantitative comparisons of cuticular hydrocarbon profiles were made between males and females, different age groups and between a standard laboratory strain and a recently colonized strain of A. aegypti. These results provide baseline data for further studies on the possible role of mosquito cuticular hydrocarbons in the modification of mating behaviour.
Comparison of attractiveness in Japan and China of three synthetic pheromone blends based on geographic variations in the rice leaffolder, Cnaphalocrocis medinalis (Lepidoptera: Pyralidae)
Authors: Kawazu K. , Nagata K. , Zhang Z. , Sugie H. , Tatsuki S. 
Published: February 2003

AbstractField bioassays using three different synthetic sex pheromone blends (Indian, Philippine and Japanese) based on geographic variations of Cnaphalocrocis medinalis Guenée were carried out at 11 sites in Japan and in Hangzhou, China. In all of the tests, only the Japanese pheromone blend attracted a significant number of male moths, while the Indian and Philippine pheromone blends showed no marked activity. The findings in Japan showed no evidence that moths of Philippine or Indian origin were able to migrate to Japan. The results from China also showed that most populations of C. medinalis in the Hangzhou region responded to the Japanese blend. This is consistent with the current hypothesis that most populations of C. medinalis in Japan are migrants from areas to the south of the Yangzhe Valley, including the region surrounding Hangzhou, China. Furthermore, populations in the Hangzhou region can not hibernate, but are considered migrants from the southernmost parts of China and southeast Asian countries such as Vietnam where they breed continuously. Consequently, at least some populations in these areas may respond to the Japanese pheromone blend.
Variation in the life cycle and morphology of the tobacco host-race of Myzus persicae (Hemiptera: Aphididae) in relation to its geographical distribution
Authors: Kephalogianni T.E. , Tsitsipis J.A. , Margaritopoulos J.T. , Zintzaras E. , Delon R. , Martin I. Blanco , Schwaer W. 
Published: February 2003

AbstractMorphological variation and life cycle category were examined in 121 clones of Myzus persicae (Sulzer). The clones were collected from tobacco from three localities in Greece (Xanthi, Nea Efessos and Naphplion), one in Germany (Rheinstetten), one in France (Bergerac) and one in Spain (Madrid). Before morphometrics, all aphids were laboratory-reared on potato. The morphological variation was investigated using both canonical variates analysis and a novel non-parametric classification tree method. The life cycle category was examined by rearing the clones for three generations under short day conditions. In Nea Efessos a relative high proportion of clones was found to overwinter as eggs on the primary host. In the other regions all collected clones were non-holocyclic. Intermediate genotypes were found in all regions at percentages ranging from 4.0 to 24.0%. Androcyclic clones were found only in Xanthi, Greece (4.0%) and Rheinstetten, Germany (16.7%). The canonical variates analysis and the tree classification method revealed important intrapopulation polymorphisms in clones from Bergerac, Nea Efessos and Madrid. Both methods separated the populations originating from Greece from those collected elsewhere in western Europe. The observed morphological variation was probably due to genetic differences, since all clones were reared in a common environment. The results are discussed in relation to factors responsible for genetic divergence in M. persicae populations.
Influence of temperature on pea aphid Acyrthosiphon pisum (Hemiptera: Aphididae) resistance to natural enemy attack
Authors: Stacey D.A. , Fellowes M.D.E. 
Published: February 2003

AbstractThe ability to resist or avoid natural enemy attack is a critically important insect life history trait, yet little is understood of how these traits may be affected by temperature. This study investigated how different genotypes of the pea aphid Acyrthosiphon pisum Harris, a pest of leguminous crops, varied in resistance to three different natural enemies (a fungal pathogen, two species of parasitoid wasp and a coccinellid beetle), and whether expression of resistance was influenced by temperature. Substantial clonal variation in resistance to the three natural enemies was found. Temperature influenced the number of aphids succumbing to the fungal pathogen Erynia neoaphidis Remaudière & Hennebert, with resistance increasing at higher temperatures (18 vs. 28°C). A temperature difference of 5°C (18 vs. 23°C) did not affect the ability of A. pisum to resist attack by the parasitoids Aphidius ervi Haliday and A. eadyi Starý, González & Hall. Escape behaviour from foraging coccinellid beetles (Hippodamia convergens Guerin-Meneville) was not directly influenced by aphid clone or temperature (16 vs. 21°C). However, there were significant interactions between clone and temperature (while most clones did not respond to temperature, one was less likely to escape at 16°C), and between aphid clone and ladybird presence (some clones showed greater changes in escape behaviour in response to the presence of foraging coccinellids than others). Therefore, while larger temperature differences may alter interactions between Acyrthosiphon pisum and an entomopathogen, there is little evidence to suggest that smaller changes in temperature will alter pea aphid–natural enemy interactions.
Production of sexual morphs by apterous virginoparae of Myzus persicae (Hemiptera: Aphididae) in relation to pre- and postnatal exposure to short day conditions
Authors: Margaritopoulos J.T. , Tsitsipis J.A. 
Published: February 2003

AbstractThe production of males and females by apterae of a holocyclic clone of Myzus persicae (Sulzer) was studied in the laboratory by transferring apterous virginoparae from long day to short day conditions at different stages of their pre- and post-natal development. Prenatal exposure was also examined in nine additional clones coming from different regions of Greece. By increasing the number of short day cycles at 17°C, the aphids switched to male production earlier and produced more males. The highest mean number of male progeny was observed in apterae that were transferred to short day conditions 13–14 days prenatally. Apterae that were transferred to short day conditions after the fourth nymphal instar produced only females. Apterous virginoparae were produced by aphids that were transferred to short day conditions 0–1 days prenatally or postnatally. Aphids, given short days prenatally or in the first instar, produced alate female progeny that were all gynoparae. The later the instar aphids were transferred to short day conditions the fewer the gynoparae produced among their female progeny. A reduction in the total number of progeny and embryos per ovariole was observed as aphids were transferred to short day conditions in earlier stages of their development. The increase in male production, which follows the increase in the duration of long night exposure, was also observed in the additional eight out of nine examined clones.