bluuebunny/crossref_metadata_2025 huggingface dataset:
Comparison of formation of reactive conformers for the S
N
2 displacements by CH
3
CO\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy}\usepackage{mathrsfs}\setlength{\oddsidemargin}{-69pt}\begin{document}\begin{equation*}{\mathrm{_{2}^{-}}}\end{equation*}\end{document} in water and by Asp124-CO\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy}\usepackage{mathrsfs}\setlength{\oddsidemargin}{-69pt}\begin{document}\begin{equation*}{\mathrm{_{2}^{-}}}\end{equation*}\end{document} in a haloalkane dehalogenase
Authors: Hur Sun , Kahn Kalju , Bruice Thomas C.
Published: March 2003

The S
N
2 displacement of Cl
−
from 1,2-dichloroethane by acetate (CH
3
CO

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) in water and by the carboxylate of the active site aspartate in the haloalkane dehalogenase of
Xanthobacter autothropicus
have been compared by using molecular dynamics simulations. In aqueous solution, six families of contact-pair structures (I–VI) were identified, and their relative concentrations and dissociation rate constants were determined. The near attack conformers (NACs) required for the S
N
2 displacement reaction are members of the IV (CH
3
CO
O
−
⋅ ⋅ ⋅
C
H
2
(Cl)CH
2
Cl) family and are formed in the sequence II→III→IV→NAC. The NAC subclass is defined by the —CO
O
−
⋅ ⋅ ⋅
C
—Cl contact distance of ≤3.41 Å and the —CO
O
−
⋅ ⋅ ⋅
C
—
Cl
angle of 157–180°. The mole percentage of NACs is 0.16%, based on the 1 M standard state. This result may be compared with 13.4 mole percentage of NACs in the Michaelis complex in the enzyme. It follows that NAC formation in the enzyme is favored by 2.6 kcal/mol. Because reaction coordinates from S to TS, both in water and in the enzyme, pass via NAC (i.e., S → NAC → TS), the reduction in the S → NAC barrier by 2.6 kcal/mol accounts for ≈25% of the reduction of total barrier in the S → TS (10.7 kcal/mol). The remaining 75% of the advantage of the enzymatic reaction revolves around the efficiency of NAC → TS step. This process, based on previous studies, is discussed briefly.
Subtype-selective reconstitution of synaptic transmission in sympathetic ganglion neurons by expression of exogenous calcium channels
Authors: Mochida Sumiko , Westenbroek Ruth E. , Yokoyama Charles T. , Itoh Kanako , Catterall William A.
Published: March 2003

Fast cholinergic neurotransmission between superior cervical ganglion neurons (SCGNs) in cell culture is initiated by N-type Ca
2+
currents through Ca
v
2.2 channels. To test the ability of different Ca
2+
-channel subtypes to initiate synaptic transmission in these cells, SCGNs were injected with cDNAs encoding Ca
v
1.2 channels, which conduct L-type currents, Ca
v
2.1 channels, which conduct P/Q-type Ca
2+
currents, and Ca
v
2.3 channels, which conduct R-type Ca
2+
currents. Exogenously expressed Ca
v
2.1 channels were localized in nerve terminals, as assessed by immunocytochemistry with subtype-specific antibodies, and these channels effectively initiated synaptic transmission. Injection with cDNA encoding Ca
v
2.3 channels yielded a lower level of presynaptic labeling and synaptic transmission, whereas injection with cDNA encoding Ca
v
1.2 channels resulted in no presynaptic labeling and no synaptic transmission. Our results show that exogenously expressed Ca
2+
channels can mediate synaptic transmission in SCGNs and that the specificity of reconstitution of neurotransmission (Ca
v
2.1 > Ca
v
2.3 ≫ Ca
v
1.2) follows the same order as in neurons
in vivo
. The specificity of reconstitution of neurotransmission parallels the specificity of trafficking of these Ca
v
channels to nerve terminals.
A global representation of the protein fold space
Authors: Hou Jingtong , Sims Gregory E. , Zhang Chao , Kim Sung-Hou
Published: March 2003

One of the principal goals of the structural genomics initiative is to identify the total repertoire of protein folds and obtain a global view of the “protein structure universe.” Here, we present a 3D map of the protein fold space in which structurally related folds are represented by spatially adjacent points. Such a representation reveals a high-level organization of the fold space that is intuitively interpretable. The shape of the fold space and the overall distribution of the folds are defined by three dominant trends: secondary structure class, chain topology, and protein domain size. Random coil-like structures of small proteins and peptides are mapped to a region where the three trends converge, offering an interesting perspective on both the demography of fold space and the evolution of protein structures.
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

Genetic 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

The 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

Herd 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

Homegardens 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

Reforestation 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

The 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

During 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

Four 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

The 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

The 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

Field 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

Morphological 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

The 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

The 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.
Key-factor analysis of immature stages of Aedes scapularis (Diptera: Culicidae) populations in southeastern Brazil
Authors: Casanova C. , do Prado A.P.
Published: February 2003

Development times and mortality factors were investigated for populations of Aedes scapularis (Rondani) occurring in natural temporary ground pools in southeastern Brazil. Analysis of life tables by the key-factor method showed that mortality caused by desiccation of breeding sites was the principal factor accounting for fluctuations in population sizes throughout the study period. For cohorts that completed development, mortality attributed to predation by aquatic insects ranged from 68 to 96% and was the most important cause of death. In these cohorts, final population size was determined by the high mortality rates that occurred during the fourth larval instar and pupal stages; however, the key-factor best accounting for the population fluctuations was predation of fourth instar larvae. The short mean time of 7.1 days for synchronous development of the larvae and the lack of evidence of density-dependent mortality suggested that the A. scapularis populations were not strongly regulated and can attain relatively high densities.
Digestive proteinases in Lasioderma serricorne (Coleoptera: Anobiidae)
Authors: Oppert B. , Hartzer K. , Zuercher M.
Published: February 2003

The cigarette beetle, Lasioderma serricorne (Fabricius), is a common pest of stored foods. A study of digestive proteinases in L. serricorne was performed to identify potential targets for proteinaceous biopesticides, such as proteinase inhibitors. Optimal casein hydrolysis by luminal proteinases of L. serricorne was in pH 8.5–9.0 buffers, although the pH of luminal contents was slightly acidic. Results from substrate and inhibitor analyses indicated that the primary digestive proteinases were serine proteinases. The most effective inhibitors of caseinolytic hydrolysis were from soybean (both Bowman Birk and Kunitz), with some inhibition by chymostatin, N-TOSYL-L-phenylalanine chloromethyl ketone, and leupeptin. Casein zymogram analysis identified at least eight proteolytic activities. Activity blot analyses indicated one major proteinase activity that hydrolysed the trypsin substrate N-α-benzoyl-L-arginine ρ-nitroanilide, and three major proteinase activities that hydrolysed the chymotrypsin substrate N-succinyl ala-ala-pro-phe ρ-nitroanilide. The absence of cysteine, aspartic, and metallo proteinases in L. serricorne digestion was evidenced by the lack of activation by thiol reagents, alkaline pH optima, and the results from class-specific proteinase inhibitors. The data suggest that protein digestion in L. serricorne is primarily dependent on trypsin- and chymotrypsin-like proteinases.
Newly imported larval parasitoids pose minimal competitive risk to extant egg–larval parasitoid of tephritid fruit flies in Hawaii
Authors: Wang X.G. , Messing R.H.
Published: February 2003

Competitive displacement of fruit fly parasitoids has been a serious issue in the history of fruit fly biological control in Hawaii. This concern regarding competitive risk of new parasitoids has led to an overall tightening of regulations against the use of classical biological control to manage fruit flies. Fopius arisanus (Sonan), an egg–larval parasitoid, is the most effective natural enemy of tephritid fruit flies in Hawaii. This study evaluated the competitive risk of two recently introduced larval parasitoids, Diachasmimorpha kraussii Fullaway and Psyttalia concolor (Szépligeti), to F. arisanus attacking the Mediterranean fruit fly, Ceratitis capitata (Wiedemann). Fopius arisanus won almost all intrinsic competitions against both larval parasitoids through physiological suppression of egg development. 83.3% of D. kraussii eggs and 80.2% of P. concolor eggs were killed within three days in the presence of F. arisanus larvae within the bodies of multi-parasitized hosts. The mechanism that F. arisanus employs to eliminate both larval parasitoids is similar to that it uses against three other early established larval fruit fly parasitoids: F. vandenboschi (Fullaway), D. longicaudata (Ashmead) and D. tryoni (Cameron). It suggests that introduction of these larval parasitoids poses minimal competitive risk to F. arisanus in Hawaii.
The influence of crop management on banana weevil, Cosmopolites sordidus (Coleoptera: Curculionidae) populations and yield of highland cooking banana (cv. Atwalira) in Uganda
Authors: Rukazambuga N.D.T.M. , Gold C.S. , Gowen S.R. , Ragama P.
Published: February 2003

A field study was undertaken in Uganda using highland cooking banana (cv. Atwalira) to test the hypothesis that bananas grown under stressed conditions are more susceptible to attack by Cosmopolites sordidus (Germar). Four banana treatments were employed to create different levels of host-plant vitality: (1) high stress: intercrop with finger millet; (2) moderate stress: monoculture without soil amendments; (3) low stress: monoculture with manure; (4) high vigour: monoculture with continuous mulch and manure. Adult C. sordidus were released at the base of banana mats 11 months after planting and populations were monitored for three years using mark and recapture methods. Cosmopolites sordidus density was greatest in the mulched plots which may have reflected increased longevity and/or longer tenure time in moist soils. Lowest C. sordidus numbers were found in intercropped banana. Damage, estimated as percentage corm tissue consumed by larvae, was similar among treatments. However, the total amount of tissue consumed was greater in mulched banana than in other systems. Plants supporting the heaviest levels of C. sordidus damage displayed bunch size reductions of 40–55%. Banana yield losses ranged from 14–20% per plot with similar levels in the intercropped and mulched systems. Yield reductions, reported as t ha-1, were twice as high in the mulched system as in the intercrop. The results from this study indicate that C. sordidus problems are not confined to stressed banana systems or those with low levels of management, but that the weevil can also attain pest status in well-managed and productive banana stands.
Host location, survival and fecundity of the Oriental rat flea Xenopsylla cheopis (Siphonaptera: Pulicidae) in relation to black rat Rattus rattus (Rodentia: Muridae) host age and sex
Authors: Mears S. , Clark F. , Greenwood M. , Larsen K.S.
Published: February 2003

Host choice and fecundity are two factors that may contribute to the variation in flea counts observed when assessing the potential risk of flea-borne transmission of pathogens from rodents to humans. Using the black rat, Rattus rattus Linnaeus, as host the effects of age and sex on host choice and fecundity of the Oriental rat flea, Xenopsylla cheopis Rothschild, were examined experimentally at 25°C and 80% rh. During the first two days of emergence from cocoons, female fleas dominated the sex ratio by 4:1 but from the third day onwards this switched to a male-dominated sex ratio of 4:1. The sex of the flea did not influence their host-seeking behaviour. Newly emerged fleas of both sexes were not influenced by the rat‘s presence and at seven days old both sexes demonstrated similar levels of attraction toward the rat host. The sex of the rat did not affect flea host-seeking behaviour. There was a 50–70% decline in the initial number of adult fleas during the first week after their release onto a rat host, and this decline was greatest on juvenile rats. Flea fecundity was also significantly lower on juvenile rat hosts but no differences due to the sex of the rat were observed. This experimental study supports the hypothesis that differences in flea count due to host sex, reported in field surveys, result from sexual differences in host behaviour and not from discriminatory host-seeking behaviour by X. cheopis. Differences in flea count due to host age may be affected by differences in X. cheopis fecundity, which may itself be mediated by host behaviour such as grooming.
Honeybee, Apis mellifera (Hymenoptera: Apidae), leaf damage on Alnus species in Uganda: a blessing or curse in agroforestry?
Authors: Nyeko P. , Edwards-Jones G. , Day R.K.
Published: February 2003

It is a dictum that Apis mellifera Linnaeus is innocuous in agricultural ecosystems. This study provides the first record of A. mellifera as a significant defoliator of Alnus species. Careful field observations coupled with microscopic examination provided convincing evidence implicating A. mellifera as the cause of leaf perforation on Alnus species in Uganda. Apis mellifera was observed foraging selectively on young Alnus leaves and buds in search of a sticky substance, apparently propolis. In so doing, the bee created wounds that enlarged and caused tattering of Alnus leaves as they matured. Biological surveys indicated that the damage was prevalent and occurred widely, particularly on Alnus acuminata Kunth in Uganda. Incidence of the Apis mellifera damage on Alnus acuminata peaked in the dry season, with up to 90% of leaves emerging per shoot per month damaged, and was lowest in the wet months during peak leaf emergence. Apis mellifera leaf damage was consistently higher on Alnus acuminata than A. nepalensis D. Don., on saplings than mature trees, and on sun exposed than shaded leaves. The activity of honeybees may be detrimental to the productivity of Alnus, yet the substance for which the insect forages on Alnus is a resource with potential economic importance.
Survival and development of different life stages of three Ceratitis spp. (Diptera: Tephritidae) reared at five constant temperatures
Authors: Duyck P.F. , Quilici S.
Published: February 2003

Fruit flies (Diptera: Tephritidae) are the most damaging pests on fruit crops on Réunion Island, near Madagascar. Survival and development of the Mediterranean fruit fly, Ceratitiscapitata (Wiedemann), the Natal fruit fly, C. rosa Karsch and the Mascarenes fruit fly, C. catoirii Guérin-Mèneville were compared at five constant temperatures spanning 15 to 35°C. Durations of the immature stages of C. capitata, C. rosa and C catoirii ranged from 14.5–63.8, 18.8–65.7 and 16.8–65.8 days, respectively, at 30–15°C. The lower developmental threshold and thermal constant were calculated using the temperature summation model. The thermal constant for total development of the immature stages of C. capitata, C. rosa and C. catoirii were 260, 405 and 356 DD, respectively. Species differed mainly during the larval stages and ovarian maturation period, with smaller differences in the egg stage. Ceratitis rosa appeared to be better adapted to low temperatures than the two other species as it showed a lower larval developmental threshold of 3.1°C compared to 10.2°C for C. capitata and 8.9°C for C. catoirii. Overall, C. catoirii had a low survival rate within the range of temperatures studied. The different responses of the three Ceratitis species to various temperatures explain to some extent their distribution on the island. The results obtained will be used for optimizing laboratory rearing procedures and for constructing computer simulation models to predict fruit fly population dynamics.
Attraction of Phytoseiulus persimilis (Acari: Phytoseiidae) towards volatiles from various Tetranychus urticae-infested plant species
Authors: van den Boom C.E.M. , van Beek T.A. , Dicke M.
Published: February 2003

Plants infested with the spider mite Tetranychus urticae Koch, may indirectly defend themselves by releasing volatiles that attract the predatory mite Phytoseiulus persimilis Athias-Henriot. Several plants from different plant families that varied in the level of spider mite acceptance were tested in an olfactometer. The predatory mites were significantly attracted to the spider mite-infested leaves of all test plant species. No differences in attractiveness of the infested plant leaves were found for predatory mites reared on spider mites on the different test plants or on lima bean. Thus, experience with the spider mite-induced plant volatiles did not affect the predatory mites. Jasmonic acid was applied to ginkgo leaves to induce a mimic of a spider mite-induced volatile blend, because the spider mites did not survive when incubated on ginkgo. The volatile blend induced in ginkgo by jasmonic acid was slightly attractive to predatory mites. Plants with a high degree of direct defence were thought to invest less in indirect defence than plants with a low degree of direct defence. However, plants that had a strong direct defence such as ginkgo and sweet pepper, did emit induced volatiles that attracted the predatory mite. This indicates that a combination of direct and indirect defence is to some extent compatible in plant species.
Geographical variation in larval susceptibility of the diamondback moth, Plutella xylostella (Lepidoptera: Plutellidae) to Bacillus thuringiensis spore–crystal mixtures and purified crystal proteins and associated resistance development in India
Authors: Mohan M. , Gujar G.T.
Published: February 2003

The susceptibility of larvae of the diamondback moth, Plutella xylostella Linnaeus to purified crystal proteins and spore–crystal preparations of Bacillus thuringiensis was investigated for 13 populations from seven states in India. The LC50 (μg ml−1, 48 h) values of Cry proteins for different populations of P. xylostella ranged from 0.14–3.74 (Cry1Aa), 0.007–1.25 (Cry1Ab), 0.18–2.47 (Cry1Ac) and 0.12 – 3.0 (Cry1C). The LC50 (mg (ai) l-1, 48 h) of spore-crystal preparations ranged from 0.02–0.98 (HD-1) and 0.06–2.14 (HD-73). Significantly higher LC50 values for all tested toxins and strains were obtained with populations collected from Iruttupallam and Ottanchathiram in the southern state of Tamil Nadu, whereas some of the populations collected from the northern part of India were more susceptible than the susceptible IARI 17–65 population. The high levels of resistance in the Iruttupallam and Ottanchathiram populations to Cry1Ab suggested selection pressure by Cry1Ab, which is the predominant toxin in B. thuringiensis formulations used in India. Cry1Ab was found to be more toxic than the other toxins. The population from Iruttupallam showed increased resistance following selection with Cry1Ab in the laboratory (LC50 from 1.25 to 4.31 μg ml−1 over two generations) and also showed cross resistance to Cry1Aa and Cry1Ac. The resistance to Biobit® in the field population from Iruttupallam declined slowly; requiring c. 33 generations for an overall 10-fold decline in LC50 when the insects were reared in the laboratory without exposure to B. thuringensis.
Spatial and temporal distribution of Anopheles gambiae s.l. (Diptera: Culicidae) in two Tanzanian villages: implication for designing mosquito sampling routines
Authors: Magbity E.B. , Lines J.D.
Published: February 2003

This paper describes the spatial and temporal distribution of Anopheles gambiae s.l. Giles in two Tanzanian villages based on data collected from a five-month intensive mosquito sampling programme and analysed using Taylor's power law. The degree of spatial aggregation of female A. gambiae in each village was similar to its corresponding temporal aggregation, indicating that in designing sampling routines for estimating the abundance of mosquitoes, sampling effort should be allocated equally to houses (spatial) and nights (temporal). The analysis also showed that for a given amount of sampling effort, estimates of village-level mosquito abundance are more precise when sampling is carried out in randomly selected houses, than when the same houses are used on each sampling occasion. Also, the precision of estimating parous rates does not depend on whether mosquito sampling is carried out in the same or a random selection of houses. The implications of these findings for designing sampling routines for entomological evaluation of vector control trials are discussed.
Potential hosts of Prostephanus truncatus (Coleoptera: Bostrichidae) among native and agroforestry trees in Kenya
Authors: Nang'ayo F.L.O. , Hill M.G. , Wright D.J.
Published: February 2003

This study was carried out to establish the extent to which an invasive stored products pest, Prostephanus truncatus Horn exploits wood as a feeding and breeding resource in Kenya. Twenty seven out of 84 native and agroforestry trees and shrubs supported the breeding of P. truncatus under laboratory conditions. Adult survival (<1% to 18%) for 8 weeks was recorded on 51 tree species that did not support breeding. The breeding success of this beetle varied widely between host tree species and showed no obvious trends based on tree systematics or wood hardness. Studies of P. truncatus survival on two host tree species found that the greatest increase in the P. truncatus population occurred on stem sapwood, whilst the smallest population increase was on twigs. Breeding also varied greatly from season to season; studies on ten selected host species showed that reproduction was often greatest in wood samples collected and tested during the dry season in September. The implications of these findings for the management of P. truncatus infestations in farm stored maize are discussed.
Interspecific host discrimination and within-host competition between Encarsia formosa and E. pergandiella (Hymenoptera: Aphelinidae), two endoparasitoids of whiteflies (Hemiptera: Aleyrodidae)
Authors: Pedata P.A. , Giorgini M. , Guerrieri E.
Published: February 2003

Interspecific host discrimination and within-host competition between Encarsia formosa Gahan and Encarsia pergandiella (Howard), two endoparasitoids of whiteflies, were studied under laboratory conditions. Interspecific host discrimination was studied at two time intervals (0 h and 72 h after the first species had oviposited). Parasitized and unparasitized Trialeurodes vaporariorum (Westwood) hosts were accepted for oviposition at the same rate by the two parasitoid species. Host type did not affect the handling time of the two parasitoids. The outcome of within-host competition was investigated after females of the two species parasitized the hosts at various time intervals. In four treatments, E. pergandiella was allowed to oviposit 0, 24, 48 and 72 h after E. formosa while in the other two, E. formosa was allowed to oviposit 0 and 72 h after E. pergandiella. In four of these treatments: E. formosa following E. pergandiella at 0 and 72 h, and E. pergandiella following E. formosa at 0 and 24 h, E. pergandiella prevailed. In the host discrimination experiment (72 h interval), 20% of E. pergandiella eggs were killed by E. formosa females. Interspecific ovicide was also observed in the within-host competition experiment, in which 6% of 72-h-old E. pergandiella eggs were killed by E. formosa females.
Factors influencing pulse consumption in Latin America
Authors: Leterme Pascal , Carmenza Muũoz L.
Published: February 2003

In Latin America, pulse consumption ranges from 1 kg/capita per year (Argentina) to 25 kg/capita per year (Nicaragua). Common beans account for 87% of the total. The differences between countries, regions or groups of population within the same country can be explained by the following factors: (1) beans are very nutritious; (2) beans and maize are traditional foods and the habit of consuming them is deeply rooted in many people and communities; (3) the rural population eats more pulses than the urban population, due to geographical constraints that limit exchanges and favour consumption of locally produced foods; (4) income level, beans are still the poor man's meat; and (5) other factors, such as consumers' taste, the constraints on cooking beans, etc. The evolution of the consumption level in the future will depend on the urbanization of the population, access to processed foods and income level. Health issues would be an argument for maintaining or increasing the current consumption level.