bluuebunny/crossref_metadata_2025 huggingface dataset:
Catastrophic disturbance and vegetation on Little Slope, Lord Howe Island
Authors: PICKARD JOHN
Published: July 2006

Little Slope is a series of debris avalanche deposits below basalt cliffs 700 m high at the southern end of Lord Howe Island (31°35′S 159°05′E). There are five distinct physiographic areas on the slope, each separated by sharp boundaries which mostly correspond to boundaries between features on the cliffs above. The physiography is a consequence of a series of landslides of different, but unknown, ages. A model of the physiographic history is presented.

Each physiographic area supports a different vegetation community, also separated by sharp boundaries. The present structure of two communities, Melaleuca howeana scrub and Howea forsterana forest, is a consequence of damage by feral animals. Melaleuca scrub has replaced Cyperus lucidus sedgeland destroyed by goats (Capra hircus) browsing from 1914 until their extermination in 1955. Howea forest has a markedly unimodal age distribution with very few small individuals of the dominant palms. This is a result of the combined effects of browsing by goats on small palms, and seed predation by black rats (Rattus rattus) from the 1920s, preventing regeneration.

Unless rat numbers are periodically reduced to reduce seed predation, regeneration may be insufficient to guarantee long‐term survival of the forest.
Soils and vegetation of central Australian sandridges. IV. Soils.
Authors: BUCKLEY R. C.
Published: July 2006

Catenary patterns on central Australian sandridges are assessed for the following soil parameters: sand depth, texture, mobility and penetrability; moisture content and characteristic; organic C content, total N and extractable P, K and Ca. There are marked dune‐swale gradients in sand depth, soil texture, mobility and penetrability, moisture content at — 15 kPa, and N and organic C contents. There are dune‐swale gradients in soil Ca content at a few sites only. Soil P shows significant heterogeneity but no catenary patterns, whilst K levels are homogeneous throughout. S, Mg, Fe, Mn, Cu, Zn, B, Mo, Co and CI were also measured for a number of sandridge soils but showed no significant catenary patterns and were therefore not studied in detail.
Viable soil seed banks in disturbed lowland tropical rainforest sites in North Queensland
Authors: HOPKINS MIKE S. , GRAHAM ANDREW W.
Published: July 2006

Four 0.125 m2 soil samples, 50 mm deep, from each of eight tropical lowland rainforest sites ranging from primary and secondary forests to degraded Imperata grasslands were exposed to shade‐house conditions. Germinations of soil seeds were monitored over 28 weeks in April‐October. The viable seed banks in the primary forest (592 m‐2) and the secondary forest sites resulting from one cycle of clearing and abandonment (1300–1400 m‐2) were composed predominantly of secondary species. The viable seed banks were small in Imperata grassland sites that had been burnt regularly (200–400 m‐2) and very large (2000–3000 m‐2) in sites that had not been burnt for five years or more. The seed banks of the burnt and unburnt Imperata grassland sites were composed mostly of agricultural weeds whilst seeds of secondary rainforest trees were rare or absent. Similarities between the species composition of soil seed banks and regrowth vegetation types suggest that soil seed composition is important in determining the initial floristic composition following disturbance and that lack of seed of secondary rainforest trees is one factor which restricts re‐growth and secondary succession on degraded Imperata grasslands. Species such as Eucalyptus intermedia R. T. Bak., E. pellita F. Muell. and Imperata cylindrica (L.)Beauv. which can establish and deflect the normal rainforest secondary succession were not present in the soil seed bank, and these species appear to rely on fresh seed inputs, lignotubers or rhizomes to colonize and regenerate after disturbance.
Interactions between seedlings of Chrysanthemoides monilifera and Acacia longifolia
Authors: WEISS P. W. , NOBLE I. R.
Published: July 2006

Displacement of Acacia longifolia on coastal dunes in New South Wales by the invasive species Chrysanthemoides monilifera may be linked to the greater competitiveness by the latter in the seedling stage, as demonstrated in pot experiments. This occurs despite a lower chlorophyll concentration in shoots of C. monilifera which leads to a lower assimilation rate per unit leaf area and lower carbohydrate concentrations. However, this assimilate is spread over a greater total leaf area. Such a strategy associated with‘quantity’may thus be more important than leaf‘quality’in terms of competitiveness. In A. longifolia, the production of higher quality‘leaves’but of lower total area may be well‐suited in the often sparse native populations found in sand dunes, but appears disadvantageous when seedlings of C. monilifera also co‐exist.

The competitive advantage of C. monilifera over A. longifolia is reduced but not reversed under water stress. Under severe stress, mortality of C. monilifera is greater than that of A. longifolia in monocultures but mortality of both species is similar in mixtures. The reason appears to be that C. monilifera transpires more water per plant even though its rate of transpiration per unit leaf area is reduced under water stress because of early stomatal closure. In mixtures, faster root growth of C. monilifera ensures faster uptake of the available soil water, thus minimizing the inherent advantage in A. longifolia of its lower water use and greater efficiency.
Variation between field and laboratory populations of Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae)
Authors: WHITE G. G.
Published: July 2006

Rates of development and pupal weights were compared between seven field populations and two laboratory strains of Tribolium castaneum. Rates of development did not differ significantly between field populations, but pupal weights did vary. Laboratory strains were both slower to develop and heavier than the field populations. The data support the hypothesis that field populations undergo selection for fast development in transient habitats. The findings are discussed in the context of r and K selection in field populations and laboratory cultures.
Breeding of the bush fly, Musca vetustissima Walker, in an over‐wintering area during winter and spring
Authors: MATTHIESSEN J. N.
Published: July 2006

Field experiments in an area of south‐western Australia where bush fly (Musca vetustissima) adults occur permanently, showed that it overwintered by continuous breeding; but only two to three generations occurred between June and September. Low survival of eggs and larvae in the food (cattle dung) from May to August was associated with rainfall rather than low temperatures. High egg‐adult survival occurred in late August; lower egg and larval survival in September and early October was attributed partly to dung fauna. Egg and larval survival was high in late October until December but predation or parasitization caused low survival of puparia outside the dung. Experimental and wild adult flies were largest and therefore most fecund in early spring; smaller wild flies in late spring appeared to result from larval competition for food. Simultaneous high egg‐adult survival, high fecundity and rapidly decreasing generation times in late winter and early spring provide a basis for explaining the major increase in adult bush fly abundance observed in some areas in mid‐spring.
Biomass and nutrient distribution in eucalypt plantations growing on rehabilitated bauxite mines
Authors: WARD S. C. , PICKERSGILL G. E.
Published: July 2006

The quantities of above ground biomass and nutrients accumulated by two eucalypt forests growing on rehabilitated bauxite mines in south‐western Western Australia were determined. The plantation at one site was 7.5 years old and had no understorey. The plantation at the second site was 3.5 years old and had been sown with seed of leguminous understorey species, resulting in a dense understorey.

Similar amounts of biomass had accumulated at the two sites. However, the second site, in which the legume understorey accounted for 67% of the total above ground biomass, had about three times as much nitrogen in its biomass as the site without an understorey. There was also more sulphur in the biomass at this site. There were similar amounts of other nutrients at both sites.

The plantation with an understorey is considered more likely to develop into a forest similar to the eucalypt forest prior to mining than the plantation without an understorey.
A biogeoclimatic analysis of Nothofagus cunninghamii (Hook.) Oerst. in southeastern Australia
Authors: BUSBY JOHN R.
Published: July 2006

The geographical limits of Nothofagus cunninghamii are highly correlated with climate and appear to be more or less in equilibrium with the climate of the present century in all but one of the areas of its present range. It is suggested that suitable climates for the species occur in the highlands of northeastern Victoria and southern New South Wales, beyond its present range, and it is possible that it occurred within the predicted area prior to the last ice age. It is suggested that populations of N. cunninghamii along the northeastern edge of its present range in the Central Highlands of Victoria may be migrating northeast along a narrow corridor of apparently suitable climate to re‐occupy the postulated former range. The rate of migration would be expected to be extremely slow because of the poor dispersal ability of the species and the adverse impact of recurrent fires.
Vascular plant species‐area relationships on Nui Atoll, Tuvalu, Central Pacific: a reassessment of the small island effect
Authors: WOODROFFE COLIN D.
Published: July 2006

Nui Atoll, an isolated atoll in Tuvalu, has a total vascular flora of 86 species, including a large number of introduced species. If only the 44 species considered indigenous are examined, there exists a strong linear relationship (r2= 0.94) between the total number of species and the logarithm of island area, over the entire wide range of island sizes from 0.01 ha to 138 ha. This relationship is strong for both three species and herb species, but weak for shrub species for which there is a limited pool of potential colonists. This relationship is stronger than on other Pacific atolls and does not support the existence of a ‘small island effect’. The strong linear relationship on Nui is attributed to uniformity of reef island substrate, distribution and isodimensionality of reef islands, stability of islands and infrequency of catastrophic events and the absence of large monospecific stands, especially of shrub species, characteristic of drier atolls.
Movement and feeding patterns of Epilachna cucurbitae Richards (Coleoptera:Coccinellidae) on pumpkin and zucchini plants2
Authors: WILSON L. J.
Published: July 2006

The oviposition patterns of adults and the movement and feeding patterns of larvae of Epilachna cucurbitae on two species of cucurbits, Cucurbita maxima cv Queensland Blue and C. pepo cv Blackjack, were studied in the field and laboratory. The physical and nutritional characteristics of host plant leaves of different ages were described. Younger leaves had higher nitrogen contents but were less abundant, smaller and had higher trichome densities than older leaves. The development of first instar larvae was delayed by the leaf hairs on young and mature pumpkin leaves which prevented larvae from reaching the leaf surface to feed First instal larvae developed more quickly on leaves rich in nitrogen. Neither the total developmental time of larvae nor the size of pupae was affected by leafage because larvae on poor quality leaves compensated by eating more. Female beetles oviposited on all but the youngest and oldest leaves of the host plant. The trichomes on young leaves prevented females from attaching eggs to the leaf surface. First instar larvae remained where they hatched, but older larvae were more mobile, Changing feeding sites frequently and moving progressively to younger, more nutritious leaves. Final instar larvae moved onto adjacent vegetation to pupate. The adaptive significance of these patterns is discussed in relation to the nutritional value, hairiness and abundance of host plant leaves of different ages and the physical limitations of different larval instars.
Honeyeater population changes in relation to food availability in the Jarrah forest of Western Australia
Authors: COLLINS BRIAN G. , NEWLAND CHARLES
Published: July 2006

The numbers of honeyeaters present at particular sites in the Jarrah forest varied significantly from month to month, with peak abundance occurring between May and September. Numbers also varied from site to site, depending upon the major plant species present. Honeyeater abundance was not limited by arthropod availability, but in many instances was closely correlated with the availability of nectar, particularly that produced by Dryandra sessilis. Large honeyeaters, such as Anthochaera chrysoptera and Phylidonyris novaehollandiae, were generally most abundant at times and sites of greatest nectar production. Small honeyeaters, such as Acanthorhynchus superciliosis, were never abundant but were present for most of the year. The production of nectar between October and December was such that more honeyeaters could have been supported than were actually present. Low numbers at these times can be explained in terms of reduced foraging efficiency that would have resulted from more widely dispersed flowers, and the possible availability of more rewarding nectar resources at other sites.
Patterns of ant community organization in mesic southeastern Australia
Authors: ANDERSEN ALAN N.
Published: July 2006

study of the ants of 11 sites at Wilson's Promontory, Victoria, found that patterns of ant community organization varied markedly between habitats, being controlled by climate and vegetation structure. Community organization showed continuous change from drier sites (especially woodlands) where broadly‐adapted species ofRhytidoponerawere particularly abundant, but many other taxa were also well‐represented, to wet forests where cool‐climate specialists(Prolasiusand certainChelaner)and cryptic species (mostlySolenopsis)cotnprised almost all ants. These patterns appear to be typical of those in mesic regions of Australia, and contrast with those in the arid zone where ant faunas are dominated by highly active and aggressive species ofIridomyrmexwhich apparently play a pivotal role in community organization. The results suggest that ant communities in mesic regions are less tightly structured than those in the arid zone, and that interspecific competition is a less important factor influencing community organization. The findings of this study are briefly discussed in relation to the potential use of ants as bio‐indicators.
Pollination ecology of Christmas Bells (Blandfordia nobilis Sm.): Effects of adding artificial nectar on pollen removal and seed‐set
Authors: PYKE GRAHAM H. , DAY LYNN P. , WALE KEVIN A.
Published: July 2006

Addition of artificial nectar to Blandfordia nobilis plants increased fruit set in plants treated in December but had no apparent effect on either fruit set for plants treated in January or the amount of pollen removed per plant for either the December or January plants. Increased nectar production would therefore have conferred no apparent reproductive advantage to a plant flowering in January and would have been advantageous to a December flowering plant only in terms of reproduction as a female, and not in terms of male reproduction.
The effects of tree clearing and pasture establishment on a population of mound‐building termites (Isoptera) in North Queensland
Authors: HOLT J. A. , COVENTRY R. J.
Published: July 2006

Populations of mound‐building termites were examined in a semi‐arid tropical woodland and in an adjacent area cleared of trees and sown with Urochloa mosambicensis 14 years previously. In that period both the density and diversity of the mound‐building termite populations were reduced in the cleared area. Only two of the six mound‐building species found in the undisturbed woodland recolonized the pasture. These species, Amitermes vitiosus and Nasutitermes longipennis, both detritus feeders, are able to survive on the Urochloa leaf material and cattle dung. The absence of the harvester species Tumulitermes pastinator, Drepanotermes perniger and Drepanotermes rubriceps from the Urochloa pasture is attributed to the lack of acceptable food resources.
Diversity and seasonality of adult Trichoptera captured in a light‐trap at Yuccabine Creek, a tropical Australian rainforest stream
Authors: BENSON L. J. , PEARSON R. G.
Published: July 2006

Seventeen light‐trap samples were taken over a 20 month period at Yuccabine Creek, an upland rainforest stream in north‐eastern Queensland. Seventy‐eight species of Trichoptera were recorded from a total catch of 6431 individuals. The fauna was dominated by the Hydroptilidae (25 species and 5131 individuals) and, though composed primarily of Torresian genera, some Bassian elements were recorded. A seasonal pattern of change of abundance was observed with the majority of tax a exhibiting maxima between December and January (summer) and minima between July and September (winter).
Chronic treatment with trimetazidine reduces the upregulation of atrial natriuretic peptide in heart failure
Authors: Morgan Eric E. , Young Martin E. , McElfresh Tracy A. , Kung Theodore A. , Hoit Brian D. , Chandler Margaret P. , Stanley William C.
Published: July 2006

Trimetazidine (TMZ) is effective for the treatment of ischemic cardiomyopathy; however, little is known about the effect of TMZ in established injury‐induced heart failure. When rats with established infarct‐induced heart failure were treated for 12 weeks with TMZ there was no effect on left ventricular function or dilation, or on mRNA expression of fatty acid oxidation enzymes. On the other hand, TMZ significantly reduced atrial natriuretic peptide mRNA levels compared with untreated rats.
Mental Disorders, Comorbidity, and Postrunaway Arrests Among Homeless and Runaway Adolescents
Authors: Chen Xiaojin , Thrane Lisa , Whitbeck Les B. , Johnson Kurt
Published: July 2006

This study examined the associations between lifetime mental disorder, comorbidity, and self‐reported postrunaway arrests among 428 (187 males, 241 females) homeless and runaway youth. The analysis examined the pattern of arrests across five lifetime mental disorders (alcohol abuse, drug abuse, conduct disorder, major depressive episode, and posttraumatic stress disorder). The adolescents, ranging from 16 to 19 years old, were interviewed directly on the streets and in shelters in four Midwestern states using computer‐assisted personal interviewing. Extensive self‐reports of early life history, behaviors since running away from home, and diagnostic interviewing (UM‐CIDI and DISC‐R) were used to estimate possible disorders. There was a high level of postrunaway arrests reported by the youth; more than half were arrested at least once after the initial runaway, with the average of 4.4 times. Consistent with the hypotheses, there were differential associations between individual mental disorders and involvement with the criminal justice system. Only externalizing disorders such as substance abuse and conduct disorder were related to arrest. Street youth with multiple externalizing and internalizing disorders were more likely to be arrested than nondisordered youths.
Trajectories of Prosocial Behavior and Physical Aggression in Middle Childhood: Links to Adolescent School Dropout and Physical Violence
Authors: Kokko Katja , Tremblay Richard E. , Lacourse Eric , Nagin Daniel S. , Vitaro Frank
Published: July 2006

Trajectories of prosocial behavior and physical aggression between 6 and 12 years of age were identified for a sample (N=1,025) of males. The trajectories were then used to predict school dropout and physical violence at age 17. Using a group‐based semi‐parametric method, two trajectories of prosociality (low and moderate declining) and three trajectories of physical aggression (low, moderate, and high declining) were obtained. Only a small minority (3.4%) of the boys were characterized by both high aggression and moderate prosociality. Physical aggression predicted both school dropout and physical violence, but contrary to expectations, prosocial behavior did not have additive or protective effects.
Changes in College Women's Attitudes Toward Sexual Intimacy
Authors: Gilmartin Shannon K.
Published: July 2006

Inspired by the work of Tolman and others, this longitudinal qualitative study was designed to explore how women feel about sexual intimacy in the first year of college and how these feelings change over time. In‐depth interviews with 14 young women were conducted over a period of 2 years. Findings suggest that the valence of sexual intimacy shifts by the end of women's sophomore year, but this shift in valence is not necessarily accompanied by a stronger sense of sexual agency, given that terms of the sexual and relational landscape to which women must adjust seem to primarily benefit cultural constructions of masculinity.
The effect of whole‐blood donor adverse events on blood donor return rates
Authors: Newman Bruce H. , Newman Daniel T. , Ahmad Raffat , Roth Arthur J.
Published: July 2006

BACKGROUND: Some blood donation–related adverse events (AEs) can negatively impact the blood donor return rate (BDRR) and decrease donor retention.

STUDY DESIGN AND METHODS: One‐thousand randomly selected whole‐blood donors were interviewed 3 weeks after a 525‐mL index whole‐blood donation for seven AEs. The number of return visits and duration of follow‐up were recorded for each of the 1000 donors. A negative binomial regression analysis was used to determine the contribution of the four most common AEs to the BDRR, and interactions between these AEs were also evaluated.

RESULTS: The four most common AEs were bruise alone (15.1%), sore arm “alone” (7.0%), fatigue “alone” (5.1%), and donor reaction “alone” (4.2%), where “alone” is defined to also include donors who had a bruise but no other AE. The estimated BDRR for donations without AEs was 1.32 visits per year. The estimated BDRRs for the four most common AEs were: bruise alone, 1.32 visits per year; sore arm alone, 1.30 visits per year (2% reduction in BDRR); fatigue alone, 1.06 visits per year (20% reduction in BDRR); and donor reaction alone, 0.87 visits per year (34% reduction in BDRR). The BDRR for donor reaction, fatigue, and sore arm together was 0.20 visits per year (85% reduction in BDRR).

CONCLUSION: Donor reaction had the most negative impact on the BDRR. There appears to be a synergistic effect between donor reaction, fatigue, and sore arm. Theoretically, amelioration of some AEs has the potential to improve BDRRs.
Fish assemblage structure and aquatic pollution in a Brazilian stream: some limitations of diversity indices and models for environmental impact studies
Authors: Lima‐Junior S. E. , Cardone I. B. , Goitein R.
Published: July 2006

Abstract –  The aim of this study was to describe and quantify the effect of aquatic pollution on the fish assemblage structure of the Corumbataí River (Brazil), by comparing two sites with different water quality characteristics. The results revealed that abundance of individuals was low at the polluted site (B). However, the two sites did not differ significantly in species richness (total and average). This fact contradicts theories stating that portions where the transverse area of the channel is larger should present a higher biological richness. It was also observed that the ichthyofauna of site B had higher evenness, and, consequently, a tendency to a higher diversity than that at site A. This demonstrates that diversity estimates should be used cautiously in environmental impact studies, as they do not necessarily indicate better conditions of communities living in more preserved environments.
Conformational stability of 17β‐hydroxysteroid dehydrogenase from the fungus Cochliobolus lunatus
Authors: Ulrih Nataša Poklar , Lanišnik Rižner Tea
Published: July 2006

The functional activities of proteins are closely related to their molecular structure and understanding their structure–function relationships remains one of the intriguing problems of molecular biology. We investigated structural changes in 17β‐hydroxysteroid dehydrogenase from the fungus Cochliobolus lunatus (17β‐HSDcl) induced by pH, temperature, salt, urea, guanidine hydrochloride, and coenzyme NADPH binding. At 25 °C and within the relatively narrow pH range of 7.0–9.0, 17β‐HSDcl exists in its native conformation as a dimer. This native conformation is thermally stable up to 40 °C in this pH range. At 25 °C and pH 2.0 in the presence of 150–300 mm NaCl, 17β‐HSDcl forms soluble aggregates enriched in α‐helical and β‐sheet structures. At higher temperatures and NaCl concentrations, these soluble aggregates start to precipitate. The denaturants urea and guanidine hydrochloride unfold 17β‐HSDcl at concentrations of 1.2 and 0.4 m, respectively. Binding of the coenzyme NADPH to 17β‐HSDcl causes local structural changes that do not significantly affect the thermal stability of this protein.
Lightweight Ballistic with Additional Stab Protection Made of Thermally Sprayed Ceramic and Cermet Coatings on Aramide Fabrics
Authors: Gadow Rainer , Von Niessen Konstantin
Published: July 2006

Ceramic and cermet coatings on fiber fabrics used in lightweight protection should enhance their performance in stab protection. Based on thermal spray technologies a coating process for hard material layers even on temperature‐sensitive fiber substrates has been developed, so that the coated fabrics retain their flexibility. High‐speed and high‐rate cermet and ceramic coatings are deposited with simultaneous substrate cooling in order to apply thick, hard, and refractory cermet and oxide ceramic coatings. These coatings can be applied on lightweight aramide fabrics without damaging the fibers. The hard material, aramide composite fabric combines the advantages of aramide fabrics and hard, refractory materials. A fully flexible, highly tenacious and lightweight fabric with a hard and refractory top coating is developed. The penetration of knives and blades through such hard material‐coated multilayer fabrics is effectively prevented.
Application of Nanostructured ASP Precursors for Processing CaCuMn6O12 Colossal Magnetoresistance Ceramics
Authors: Chekanova Anastasia E. , Philippov Yaroslav Yu. , Goodilin Eugene A. , Volkova Olga S. , Veresov Alexander G. , Tretyakov Yury D. , Goodilin Eugene A. , Eremina Elena A. , Tretyakov Yury D. , Volkova Olga S. , Klimov Konstantin V. , Vasiliev Alexander N. , Syrov Yury V.
Published: July 2006

Nanostructured precursors prepared by ultrasonic aerosol spray pyrolisys at 750–950°C in air were applied for the first time to obtain Ca(Cu,Mn)7O12 colossal magnetoresistance ceramics with a unique submicron necked‐grain microstructure. It was observed that a high contribution of intergrain tunneling magnetoresistance results in a 10–20% difference in functional properties as dependent on morphological features of hollow precursor microspheres ASP processed at a given temperature.
Tracing the Origin of Dietary Protein in Tropical Dry Forest Birds1
Authors: Herrera M. L. Gerardo , Hobson Keith A. , Martínez J. Carlos , Méndez C. G.
Published: July 2006

Fundamental to our understanding of the ecology of animal communities in the tropics is knowledge of the effect of seasonal changes in the abundance of food sources in consumer diets. We determined stable‐isotope composition (13C/12C and15N/14N) in whole blood of 14 resident avian species in a tropical dry forest to quantify the origin of their assimilated protein. We used a probabilistic approach (IsoSource) to estimate the relative contribution of C3plants, CAM‐C4plants, C3insects, and CAM‐C4insects during the dry and rainy seasons. IsoSource iteratively creates each possible combination of source contribution and produces a distribution of all feasible combinations that adequately predict the observed isotopic signature of the consumer. Granivore–frugivores and granivore–frugivore–insectivores were modeled as predominantly dependent upon plants whereas insectivorous birds were modeled to derive protein almost exclusively from insects. Between these extremes there were several species using mixed diets such as insectivore–frugivores or insectivore–granivores. In most species, virtually all assimilated food was of C3origin with the exception of Ruddy Ground‐Doves (Columbina talpacoti) in which CAM or C4plants contributed significantly. Seasonal changes in relative food source contribution were followed in eight species of birds. Of these species, White‐tipped Doves (Leptotila verreauxi), Grayish Saltators (Saltator coerulescens), and Social Flycatchers (Myiozetetes similis) increased their use of insects in the rainy season, in contrast to Great Kiskadees (Pitangus sulphuratus), which decreased their use of insects. Our study suggests that that diverse strategies are used by various avian species to obtain dietary proteins within seasonal habitats.
Genetic Diversity and Structure in Fragmented Populations of the Tropical Orchid Myrmecophila christinae var christinae1
Authors: Vargas Carlos F. , Parra‐Tabla Víctor , Feinsinger Peter , Leirana‐Alcocer Jorge
Published: July 2006

In recent years the coastal dune vegetation of the state of Yucatan, Mexico has become highly fragmented due to clearing for development. We evaluated patterns of genetic differentiation and genetic variability among orchid populations (Myrmecophila christinae var christinae) in eight habitat fragments along a west‐to‐east disturbance gradient in which sites located on the western end began experiencing fragmentation earlier than those in the east. Leaf samples from adult individuals and juvenile plants were collected from all eight populations, and analyzed using starch‐gel electrophoresis in a lithium buffer system. Per population estimates of genetic diversity, proportion of polymorphic loci at 95 percent, mean number of alleles per locus, allelic richness, and population structure were calculated, as well as estimate comparisons between generations. Genetic diversity at the loci analyzed did not show significant differences among the eight populations. Based on the results, the model of isolation by distance does not fit the M. christinae populations under study; in some cases, populations close to one another apparently experienced very little genetic exchange. Thus, we propose that so far, fragmentation has not led to significant genetic differences between populations subject to different historical backgrounds of disturbance (i.e., time since onset of disturbance), as well as between generations within each of the M. christinae study populations. Nevertheless, the genetic characteristics of some remnant populations might change over time due to a future decrease in the opportunities for genetic exchange with other populations.
Safe in their hands? Britain’s Law Lords and human rights
Authors: Dickson Brice
Published: July 2006

This paper, which is the revised text of the first Stephen Livingstone Memorial Lecture delivered in February 2006, surveys the human rights jurisprudence of the House of Lords over the past 10 years. It considers not just how the Law Lords have responded to the Human Rights Act 1998 but also how they have developed the law on equality, asylum and immigration. In assessing whether human rights are ‘safe’ in the hands of the Law Lords, it looks, first, at how willing the Law Lords have been to engage with human rights arguments, concluding that they have relished such discourse. The piece then examines how rigorously the Lords have protected rights guaranteed by the European Convention for the Protection of Human Rights and Fundamental Freedoms 1950. The conclusion reached is that the Law Lords have been doing a good job on that front. What is preventing them from adopting an even more rights-based approach to their work in general is the UK’s stubborn adherence to the ‘dualist’ theory of international law. The author agrees with Lord Steyn that the time has come to reconsider that position.
Effect of swimming on myostatin expression in white and red gastrocnemius muscle and in cardiac muscle of rats
Authors: Matsakas Antonios , Bozzo Cyrille , Cacciani Nicola , Caliaro Francesca , Reggiani Carlo , Mascarello Francesco , Patruno Marco
Published: July 2006

The aim of this study was to test the hypothesis that swimming training might impact differentially myostatin expression in skeletal muscles, depending on fibre type composition, and in cardiac muscle of rats. Myostatin expression was analysed by real time reverse transcriptase‐polymerase chain reaction, Western blot and immunohistochemistry of the red deep portion (mainly composed of slow and type II A fibres) and in the superficial, white portion (composed of fast type II X and II B fibres) of the gastrocnemius muscle in adult male Wistar rats: (i) subjected to two consecutive swimming bouts for 3 h; (ii) subjected to intensive swimming training for 4 weeks; and (iii) sedentary control rats. Myostatin mRNA content was in all cases higher in white than in red muscles. Two bouts of swimming did not alter myostatin expression, whereas swimming training for 4 weeks resulted in a significant reduction of myostatin mRNA contents, significant both in white and red muscles but more pronounced in white muscles. Western blot did not detect any change in the amount of myostatin protein. Immunohistochemistry showed that, in control rats, myostatin was localized in presumptive satellite cells of a few muscle fibres. After training, the number of myostatin‐positive spots decreased significantly. Myostatin mRNA content in cardiac muscle was lower than in skeletal muscle and was significantly increased by swimming training. In conclusion, the results obtained showed that intense training caused a decreased expression of myostatin mRNA in white and red skeletal muscles but an increase in cardiac muscle.
Effect of frequency and pulse duration on human muscle fatigue during repetitive electrical stimulation
Authors: Kesar Trisha , Binder‐Macleod Stuart
Published: July 2006

Different combinations of stimulation frequency and intensity can generate a targeted force during functional electrical stimulation (FES). This study compared isometric performance and muscle fatigue during repetitive stimulation with three different combinations of frequency and pulse duration that produced the same initial peak forces: protocol 1 used long pulse duration (fixed at 600 μs) and 11.5 ± 1.2 Hz (low frequency); protocol 2 used 30 Hz (medium frequency) and medium pulse duration (150 ± 21 μs); and protocol 3 used 60 Hz (high frequency) and short pulse duration (131 ± 24 μs). Twenty and 60 Hz pre‐ and postfatigue testing trains were delivered at the pulse duration used by the fatiguing trains and at 600 μs pulse duration. The percentage decline in peak force between the first and last fatiguing train of each protocol was the measure of muscle performance. The declines in peak force of the 60 Hz testing trains were used to measure muscle fatigue. The 20 Hz:60 Hz peak force ratio was used as a measure of low‐frequency fatigue. The results showed that protocol 1 produced the least decline in peak force in response to the fatiguing trains, as well as the least muscle fatigue and low‐frequency fatigue when the pulse duration was maintained at the level used by the fatiguing trains. Interestingly, protocol 2 produced the least muscle fatigue, and there were no differences in the levels of low‐frequency fatigue across protocols when a comparable motor unit population was tested using 600 μs pulse duration. The results suggest that if the frequency and intensity are kept constant during FES, using the lowest frequency and longest pulse duration may maximize performance.
Heterogeneous spatial patterns of long‐term potentiation in rat hippocampal slices
Authors: Chang Payne Y. , Jackson Meyer B.
Published: July 2006

Although LTP (long‐term potentiation) of synaptic transmission has received much attention as a model for learning and memory, its function within a neural circuit context remains poorly understood. To monitor LTP over an extensive circuit, we imaged responses in hippocampal slices using a voltage‐sensitive dye. Following theta‐burst stimulation, evoked optical signals showed an increase that lasted 40 min or more. Weak stimuli only potentiated the local area around the stimulating electrode, but stronger stimuli induced LTP over a wide area with a complex and non‐uniform spatial pattern. The expression of LTP showed distinct peaks and valleys that depended on which axons were activated. Interestingly, the spatial distribution of LTP bore no relation to the spatial distribution of single‐shock responses, but closely resembled the distribution of postsynaptic spikes evoked by theta bursts. Thus, postsynaptic spikes during induction constitute a critical determinant for the expression of LTP in intact circuits.
Nicotine‐induced enhancement of synaptic plasticity at CA3–CA1 synapses requires GABAergic interneurons in adult anti‐NGF mice
Authors: Rosato‐Siri Marcelo , Cattaneo Antonino , Cherubini Enrico
Published: July 2006

The hippocampus, a key structure for learning and memory processes, receives an important cholinergic innervation and is densely packed with a variety of nicotinic acetylcholine receptors (nAChRs) localized on principal cells and interneurons. Activation of these receptors by nicotine or endogenously released acetylcholine enhances activity‐dependent synaptic plasticity processes. Deficits in the cholinergic system produce impairment of cognitive functions that are particularly relevant during senescence and in age‐related neurodegenerative pathologies. In particular, Alzheimer's disease (AD) is characterized by a selective loss of cholinergic neurons in the basal forebrain and nAChRs in particular regions controlling memory processes such as the cortex and the hippocampus. Field excitatory postsynaptic potentials were recorded in order to examine whether nicotine was able to regulate induction of long‐term potentiation at CA3–CA1 synapses in hippocampal slices from adult anti‐NGF transgenic mice (AD 11), a comprehensive animal model of AD, in which cholinergic deficits due to nerve growth factor depletion are accompanied by progressive Alzheimer‐like neurodegeneration. Both AD 11 and wild‐type (WT) mice exhibited short‐ and long‐lasting synaptic plasticity processes that were boosted by nicotine. The effects of nicotine on WT and AD 11 mice were mediated by both α7‐ and β2‐containing nAChRs. In the presence of GABAA receptor antagonists, nicotine failed to boost synaptic plasticity in AD 11 but not in WT mice, indicating that in anti‐NGF transgenic mice GABAergic interneurons are able to compensate for the deficit in cholinergic modulation of glutamatergic transmission. This compensation may occur at different levels and may involve the reorganization of the GABAergic circuit. However, patch‐clamp whole‐cell recordings from principal cells failed to reveal any change in spontaneous release of GABA following pressure application of nicotine to nearby GABAergic interneurons. Together, these experiments indicate that in AD 11 mice a rearrangement of the GABAergic circuit can ‘rescue’ nicotine‐induced potentiation of synaptic plasticity. This may be relevant for developing proper therapeutic tools useful for the treatment of AD.
Interstitial cells of Cajal: a new perspective on smooth muscle function
Authors: Sanders Kenton M. , Ward Sean M.
Published: July 2006

Interstitial cells of Cajal (ICC) were described more than 100 years ago by Ramon y Cajal. For many years these cells were identified only by non‐specific histological stains and later, more reliably, by electron microscopy. Ultrastructural features and the anatomical locations of ICC suggested important physiological roles for these cells. A breakthrough occurred in our ability to study ICC when it was recognized that antibodies for Kit could be used to identify ICC, even in living tissues. Signalling via Kit, a receptor tyrosine kinase, is also necessary for ICC development and maintenance of phenotype. Thus, blocking Kit, by a variety of techniques, caused loss of ICC in experimental animals and demonstrated the critical physiological functions of these cells in gastrointestinal motility. Loss of ICC in human gastrointestinal diseases may contribute to the motor pathologies observed. Unrestrained Kit signalling leads to the transformation of ICC and the development of gastrointestinal stromal tumours. Now ICC‐like cells have been identified in a variety of smooth muscle tissues, and the race is on to discover whether these cells have equivalent or even novel functions in organs outside the gastrointestinal tract. This perspectives article gives a short overview of the history of ICC research and directions for future investigation.
Isoform‐dependent interaction of voltage‐gated sodium channels with protons
Authors: Khan A. , Kyle J. W. , Hanck D. A. , Lipkind G. M. , Fozzard H. A.
Published: July 2006

Protons are potent physiological modifiers of voltage‐gated Na+ channels, shifting the voltage range of channel gating and reducing current magnitude (pKa∼6). We recently showed that proton block of the skeletal muscle isoform (NaV1.4) resulted from protonation of the four superficial carboxylates in the outer vestibule of the channel. We concluded that the large local negative electrostatic field shifted the outer vestibule carboxylate pKa into the physiological range. However, block was not complete; the best‐fit titration curves yielded an acid pH asymptote of 10–15%, suggesting that the selectivity filter carboxylates may not be protonated. Using HEK 293 cells stably expressing different isoforms, each with varying channel density, we demonstrate that a pH‐independent current is found in NaV1.4, but not in the cardiac isoform (NaV1.5). Mutational studies showed that absence of the pH‐independent current in NaV1.5 could be ascribed to the cysteine in domain I, just above the selectivity filter aspartate (Cys373). We suggest that this cysteine can be protonated in acid solution to produce a positive charge that blocks the pore. Competition between protons and Na+ did not exist for Na+ concentrations between 1 and 140 mm. The residual current in acid solution, when the cysteine is absent, confirms that over the range of pH values that can be achieved physiologically, the selectivity filter carboxylates are not protonated. The pH‐independent current helps to protect activation of skeletal muscle during the acidosis that occurs during exercise.
Dynamic clamp: a powerful tool in cardiac electrophysiology
Authors: Wilders Ronald
Published: July 2006

Dynamic clamp is a collection of closely related techniques that have been employed in cardiac electrophysiology to provide direct answers to numerous research questions regarding basic cellular mechanisms of action potential formation, action potential transfer and action potential synchronization in health and disease. Building on traditional current clamp, dynamic clamp was initially used to create virtual gap junctions between isolated myocytes. More recent applications include the embedding of a real pacemaking myocyte in a simulated network of atrial or ventricular cells and the insertion of virtual ion channels, either simulated in real time or simultaneously recorded from an expression system, into the membrane of an isolated myocyte. These applications have proven that dynamic clamp, which is characterized by the real‐time evaluation and injection of simulated membrane current, is a powerful tool in cardiac electrophysiology. Here, each of the three different experimental configurations used in cardiac electrophysiology is reviewed. Also, directions are given for the implementation of dynamic clamp in the cardiac electrophysiology laboratory. With the growing interest in the application of dynamic clamp in cardiac electrophysiology, it is anticipated that dynamic clamp will also prove to be a powerful tool in basic research on biological pacemakers and in identification of specific ion channels as targets for drug development.
Mechanisms underlying β2‐adrenoceptor‐mediated nitric oxide generation by human umbilical vein endothelial cells
Authors: Queen Lindsay R. , Ji Yong , Xu Biao , Young Lora , Yao Kang , Wyatt Amanda W. , Rowlands David J. , Siow Richard C. M. , Mann Giovanni E. , Ferro Albert
Published: July 2006

Endothelial β2‐adrenoceptor (β2AR) stimulation increases nitric oxide (NO) generation, but the underlying cellular mechanisms are unclear. We examined the role of l‐arginine transport and of phosphorylation of NO synthase 3 (NOS‐3) in β2AR‐mediated NO biosynthesis by human umbilical vein endothelial cells (HUVEC). To this end, we assessed l‐arginine uptake, NOS activity (from l‐arginine to l‐citrulline conversion), membrane potential (using [3H]tetraphenylphosphonium), as well as serine phosphorylation of NOS‐3 (by Western blotting and mass spectrometry), in HUVEC treated with βAR agonists or cyclic AMP‐elevating agents. β2AR stimulation increased l‐arginine transport, as did cyclic AMP elevation with either forskolin or dibutyryl cyclic AMP, and this increase was inhibitable by N‐ethylmaleimide. Blockade of l‐arginine uptake by l‐lysine inhibited NOS activity and, conversely, blockade of NOS using Nω‐nitro‐l‐arginine methyl ester (l‐NAME) inhibited l‐arginine transport. β2AR stimulation also caused a membrane hyperpolarization inhibitable by l‐NAME, suggesting that the increase in l‐arginine uptake occurred in response to NO‐mediated hyperpolarization. β2AR activation also increased NOS activity and phosphorylation of NOS‐3 on serine‐1177, and these increases were attenuated by inhibition of protein kinase A (PKA), phosphatidylinositol 3‐kinase (PI3K) or Akt, and abolished by coinhibition of PKA and Akt. These findings suggest that β2AR‐mediated NOS‐3 activation in HUVEC is mediated through phosphorylation of NOS‐3 on serine‐1177 through both the PKA and the PI3K/Akt systems, and is sustained by an increase in l‐arginine uptake resulting from NO‐mediated membrane hyperpolarization.
How should public health professionals engage with lay epidemiology?
Authors: Allmark P , Tod A
Published: July 2006

“Lay epidemiology” is a term used to describe the processes through which health risks are understood and interpreted by laypeople. It is seen as a barrier to public health when the public disbelieves or fails to act on public health messages. Two elements to lay epidemiology are proposed: (a) empirical beliefs about the nature of illness and (b) values about the place of health and risks to health in a good life. Both elements have to be dealt with by effective public health schemes or programmes, which would attempt to change the public’s empirical beliefs and values. This is of concern, particularly in a context in which the lay voice is increasingly respected. Empirically, the scientific voice of standard epidemiology should be deferred to by the lay voice, provided a clear distinction exists between the measurement of risk, which is empirical, and its weighting, which is based on values. Turning to engagement with values, health is viewed to be an important value and is discussed and reflected on by most people. Public health professionals are therefore entitled and advised to participate in that process. This view is defended against some potential criticisms.