bluuebunny/crossref_metadata_2025 huggingface dataset:
Dissatisfaction with dental care among mothers of Medicaid‐enrolled children
Authors: Milgrom Peter , Spiekerman Charles , Grembowski David
Published: February 2008

Objectives:  This paper is part of a larger study examining the impact of mothers’ having a regular source of dental care (RSDC) on utilization of dental care and oral health of their preschool children. We describe levels of satisfaction with care among mothers whose preschool children were enrolled in Medicaid in Washington State. We report mothers’ satisfaction related to having a RSDC by type of dental setting/office.

Methods:  Disproportionate stratified sampling by racial/ethnic group selected 11 305 children aged 3–6 in Medicaid in Washington State. Mothers (n = 4373) completed a mixed‐mode survey. Satisfaction with dental care was measured using the Dental Satisfaction Questionnaire (DSQ).

Results:  Overall mean DSQ was 57.1 ± 9.9 (range 18–89). A higher score indicates greater satisfaction. There was not evidence of a difference in dissatisfaction by race/ethnicity but Blacks and Hispanics were less satisfied with pain management than Whites. The majority of respondents agreed with the statement that ‘Dentists sometimes act rude to their patients.’ Satisfaction is higher for mothers who have a regular private dentist they see consistently versus having a regular dentist through a public or non‐profit clinic.

Conclusions:  The satisfaction with dental care for this population is low, and considerably lower than found in other studies for primary medical care. Steps need to be taken to increase dental satisfaction and access to private dental clinics, and to increase perceived quality and pain management of dental care in both private clinics and public/non‐profits serving low‐income populations.
COL1A2 gene polymorphisms (Pvu II and Rsa I), serum calciotropic hormone levels, and dental fluorosis
Authors: Huang Hui , Ba Yue , Cui Liuxin , Cheng Xuemin , Zhu Jingyuan , Zhang Yuling , Yan Pingping , Zhu Cairong , Kilfoy Briseis , Zhang Yawei
Published: February 2008

Objectives:  To investigate the relationship between dental fluorosis, polymorphisms in the COL1A2 gene, and serum calciotropic hormone levels.

Methods:  We conducted a case‐control study among children between 8 and 12 years of age with (n = 75) and without (n = 165) dental fluorosis in two counties in Henan Province, China. The PvuII and RsaI polymorphisms in the COL1A2 gene were genotyped using the PCR‐RFLP procedure. Calcitonin and osteocalcin levels in the serum were measured using radioimmunassays.

Results:  Children carrying the homozygous genotype PP of COL1A2 PvuII had a significantly increased risk of dental fluorosis (OR =4.85, 95% CI: 1.22–19.32) compared to children carrying the homozygous genotype pp in an endemic fluorosis village (EFV). However, the risk (OR = 1.07, 95% CI: 0.45–2.52) was not elevated when the control population was recruited from a non‐endemic fluorosis village. Additionally, fluoride levels in urine and osteocalcin levels in serum were found to be significantly lower in controls from non‐endemic villages compared to cases. However, the differences in fluoride and osteocalcin levels were not observed when cases were compared to a control population from endemic fluorosis villages.

Conclusions:  This study provides the first evidence of an association between polymorphisms in the COL1A2 gene with dental fluorosis in high fluoride exposed populations. Future studies are needed to confirm the association.
A cost‐effective simulation curriculum for preclinical endodontics
Authors: Pileggi Roberta , Glickman Gerald N.
Published: February 2008

A challenge in contemporary dental education is to achieve a smooth transition from preclinical teaching environments to patient‐care clinics in a cost‐effective manner. The preclinical endodontic courses at The University of Texas, Dental Branch at Houston provide a unique learning environment that enables the student to perform endodontic treatment on extracted teeth in a typodont, and be involved in diagnosis and treatment‐planning discussions. The specially designed stone typodont used has built‐in radiographic capability, and is mounted at each chair in the clinic. During each preclinical session, students are assigned clinical cubicles and proper aseptic protocol is followed. Students are required to wear gloves, masks and eyewear, and place a rubber dam during treatment. Written self‐assessment evaluations based upon prescribed criteria are utilised; feedback is given by faculty composed of both full‐time endodontists and graduate students who periodically rotate and are calibrated on a regular basis. In the lecture phase, clinical case scenarios are presented to reinforce concepts of diagnosis and emergency care and to help integrate endodontics with other disciplines; a Socratic‐like teaching style is established by the faculty facilitator to create an environment for developing critical‐thinking and problem‐solving skills. The overall feedback from graduating students has been very positive. Advantages of this format are an easier transition to patient management, a more keen interest in specialsation and a perceived increase in levels of confidence.
Inter‐ and size‐specific patterns of fish seasonal migration between a shallow lake and its streams
Authors: Skov C. , Brodersen J. , Nilsson P.A. , Hansson L.‐A. , Brönmark C.
Published: February 2008

Abstract – This study used passive telemetry (passive integrated transponders) to evaluate winter migration in three species of cyprinids (roach (Rutilus rutilus(L.)), white bream (Blicca bjoerkna(L.)) and rudd (Scardinius erythrophthalmus(L.))) and their potential predators (pike (Esox lucius(L.)) and perch (Perca fluviatilis(L.))) between a shallow lake and its streams. Migration patterns were investigated from October to June, and a substantial part of the roach (40%) and white bream (55%) populations tagged in the lake during autumn migrated during winter into the streams, whereas only very few piscivores (<2%) migrated. In contrast to roach and white bream, only few rudd (<6%) migrated, which is likely a consequence of different overwintering strategies, e.g., rudd overwintering in shallow highly structured habitats. Small rudd migrated more than larger rudd, whereas there were no size‐differentiated migration patterns for roach or white bream. Migration of the cyprinid fishes was generally initiated in late October and ended in May, and specific synchronised bursts of migration were observed in December, January and April, suggesting that migration is triggered by one or more proximate environmental cues. The cyprinid fishes generally entered the streams in late afternoon or in the morning, depending on season, but overall migration patterns varied between the three streams. We suggest and discuss that our results have great implications for lake management as well as for the interpretation of seasonal trophic dynamics in shallow lakes.
In vivo actions of melatonin on the innate immune parameters in the teleost fish gilthead seabream
Authors: Cuesta Alberto , Cerezuela Rebeca , Esteban M. Ángeles , Meseguer José
Published: February 2008

Abstract: Melatonin, a molecule produced in the pineal gland and retina of vertebrates, plays a major role in day–night circadian rhythms and other physiological processes, including the immune responses. Because little is known in this respect in fish, we have evaluated the in vivo role of melatonin in the main innate immune activities and the expression of immune‐relevant genes in a teleost fish, the gilthead seabream (Sparus aurataL.). An intraperitoneal injection of 1 or 10 mg melatonin/kg of body weight produced a dose–time dependent increase in circulating melatonin serum levels. Several innate immune responses such as peroxidase, phagocytic, reactive oxygen intermediates and cell‐mediated cytotoxic activities were significantly enhanced by the administration of melatonin at different sampling times. The expression of immune‐relevant genes such as interleukin‐1β, major histocompatibility complex, virus‐related response (interferon‐regulatory factor‐1 andMx) and lymphocyte markers (immunoglobulin M and T‐cell receptor for B and T lymphocytes, respectively), as analysed by semi‐quantitative reverse transcription‐polymerase chain reaction, was up‐regulated in the head–kidney of melatonin‐injected fish 1 and 3 days postinjection and decreased after 7 days. These data, together with our previous observations describing how photoperiod and in vitro melatonin treatment may affect seabream and sea bass immunology, confirm melatonin as a regulator of fish immunology. However, further studies are still needed to reveal the mechanisms underlying the direct or indirect interactions of melatonin with the fish immune system.
Melatonin enhances pro‐inflammatory cytokine levels and protects against Chagas disease
Authors: Santello Fabricia Helena , Frare Eduardo Osório , Caetano Leony Cristina , AlonsoToldo Míriam Paula , Do Prado José Clóvis
Published: February 2008

Abstract:  Pro‐inflammatory and modulatory cytokines have an essential role in host defense against human and murine Trypanosoma cruzi infection. Control of T. cruzi parasitism during the acute phase of infection is considered to be critically dependent on direct macrophage activation by cytokines. Melatonin has been proposed to regulate the immune system by affecting cytokine production in immunocompetent cells, enhancing the production of several T helper (Th)1 cytokines. The aims of this work were to evaluate in rats, the influences of exogenous melatonin treatment on T. cruzi‐infected host’s immune responses. With this in mind, several immunological parameters were analyzed, including tumor necrosis factor‐α, γ‐interferon, interleukin‐12, nitric oxide (NO) and macrophage count. The melatonin therapy was provided in one of two different treatment regimens, that is, either beginning 7 days prior to infection or concomitant with the infection. Both treatments triggered an up‐regulation of the immune response, with the concomitant treatment being more effective; in this case all cytokines studied, with exception of NO, displayed enhanced concentrations and there was a higher number of peritoneal macrophages, which displayed reduced concentrations under melatonin therapy. We conclude that melatonin plays a pivotal role in up‐regulating the Th1 immune response thus controlling parasite replication.
A study of the prosthodontic and oral health needs of an ageing psychiatric population
Authors: Bhansali Sumit , Tripathi Arvind , Tiwari S. C. , Singh Saumyendra V.
Published: February 2008

Background:  Life expectancy has increased worldwide, with India (having 8% who are senior citizens), falling into the “Greying Country” category. This ageing population constitutes a high‐risk oral health group, vis‐à‐vis impaired manual dexterity, cognitive deterioration and unmet treatment needs, which could be compounded by psychiatric morbidity.

Objective:  To assess oral health status and prosthodontic need of ageing psychiatric patients.

Materials and method:  One hundred and twenty‐five patients, aged 50 years or above, admitted to the Department of Geriatric Mental Health, King George’s Medical University, Lucknow, Uttar Pradesh, India, were examined for prosthodontic, oral health status and need, the study population being divided into groups on the basis of Bristol Activities Scale of Daily Living.

Results:  Depressive symptoms (which increased with age) and psychiatric morbidity were found to be more in females. About 98% of the population showed probing depths of more than 3 mm, with mean number of decayed/missing teeth and inability to maintain oral/denture hygiene (p < 0.001) increasing in higher disability levels. While 91.3% of the population wearing a prosthesis required new dentures, 33.3% of the study population had unfulfilled partial denture need and 28.4% had unfulfilled upper/lower complete denture need.

Conclusion:  Ageing psychiatric subjects require dental education and treatment to meet their needs.
Two‐dimensional finite element analysis of stresses developed in the supporting tissues under complete dentures using teeth with different cusp angulations
Authors: Chowdhary Ramesh , Lekha K. , Patil N.P.
Published: February 2008

Statement of problem:  The selection of appropriate teeth for complete denture occlusion is very important for long‐term success, and adequate maintenance of the residual alveolar ridge.

Purpose:  The purpose of this study was to determine the stress generated underneath the complete denture by altering the cuspal angulations of the denture teeth.

Material and methods:  A two‐dimensional finite element model of a coronal section of maxillary and mandibular complete dentures, mucosa and alveolar bone in the first molar region was designed. The occlusal aspect of the denture teeth was altered to make 33°, 20°, 0° cuspal angulation. All the nodes at the bases of maxillary and mandibular alveolar bone of finite element analysis models were restrained in all directions. A functional occlusal load of 50 N was applied through the mandibular model base. To design these models and to analyse them, EMRC’s NISA II finite element analysis computer software was used. In these models, the elements were selected (a, b, c, d, e, f) in the region where it was necessary to determine the stresses generated in both the maxillary and mandibular portions.

Results:  The results were interpreted as Von Mises stresses and were observed in pre‐defined areas. The stress patterns observed within model with each type of posterior occlusion, showed unique variations as well as some similarities.

Conclusion:  Stresses of greater magnitude were observed in cuspal teeth, 33° and 20° respectively, where as 0° teeth showed a slightly less magnitude of stress generated.
Tooth loss, denture wearing and associated factors among an elderly institutionalised Brazilian population
Authors: Ferreira Raquel Conceição , De Magalhães Cláudia Silami , Moreira Allyson Nogueira
Published: February 2008

Objective:  This cross‐sectional study assessed the prevalence and extent of tooth loss as well as denture wear and associated factors in institutionalised elderly in Brazil.

Background:  There is scarcity of research in Brazil concerning geriatric oral health issues.

Material and methods:  A sample of 335 individuals over 60 years of age, representative of the institutionalised elderly from Belo Horizonte, Brazil, were selected through a stratified sampling strategy. Data were collected from structured questionnaires, reviews of medical records and intra‐oral examinations.

Results:  Edentulousness was observed in 74.9% of the elderly and was related to age, years of study, income, length of institutionalisation, systemic diseases and mini‐mental score. Among the dentate subjects, 17.9% possessed 20 or more teeth. Approximately half the edentulous elderly (42.6%) and most of the partially dentate subjects (66.7%) did not wear dentures. The multivariate analysis showed that subjects that wear dentures were more likely to be female, possess higher incomes, be more functionally independent and married. Furthermore, the odds of wearing dentures among the elderly who had lost 13–32 teeth were 9.11 times higher than those who had lost up to 12 teeth.

Conclusion:  Tooth loss is highly prevalent in this institutionalised Brazilian population, and the prevalence of denture wear is low. The extent of tooth loss, income, functional status and marital status are important predictors for denture wear. The development of an oral health programme for these individuals should assist in their rehabilitation needs and promote in‐home care or safe transport for the elderly to a health care location.
Spine–sheath layer radiative interplay in subparsec-scale jets and the TeV emission from M87
Authors: Tavecchio Fabrizio , Ghisellini Gabriele
Published: February 2008

Simple one-zone homogeneous synchrotron self-Compton models have severe difficulties in explaining the TeV emission observed in the radio galaxy M87. Also, the site the TeV emission region is uncertain: it could be the unresolved jet close to the nucleus, analogously to what is proposed for blazars, or it could be the active knot, called HST-1, tens of parsec away. We explore the possibility that the TeV emission of M87 is produced in the misaligned subparsec-scale jet. We base our modelling on a structured jet, with a fast spine surrounded by a slower layer. In this context the main site responsible for the emission of the TeV radiation is the layer, while the (debeamed) spine accounts for the emission from the radio to the GeV band: therefore we expect a more complex correlation with the TeV component than that expected in one-zone scenarios, in which both components are produced by the same region. Observed from small angles, the spine would dominate the emission, with an overall spectral energy distribution close to those of BL Lac objects with a synchrotron peak located at low energy.
The Compton-thick quasar at the heart of the high-redshift giant radio galaxy 6C 0905+39
Authors: Erlund M. C. , Fabian A. C. , Blundell Katherine M. , Crawford Carolin S.
Published: February 2008

Our XMM–Newton spectrum of the giant, high-redshift (z = 1.88) radio galaxy 6C 0905+39 shows that it contains one of the most powerful, high redshift, Compton-thick quasars known. Its spectrum is very hard above 2 keV. The steep XMM–Newton spectrum below that energy is shown to be due to extended emission from the radio bridge using Chandra data. The nucleus of 6C 0905+39 has a column density of 3.5+1.4−0.4× 1024 cm−2 and absorption-corrected X-ray luminosity of 1.7+0.9−0.1× 1045 erg s−1 in the 2–10 keV band. A lower redshift active galaxy in the same field, SDSS J090808.36+394313.6, may also be Compton thick.
Voluntary running exercise attenuates the progression of endothelial dysfunction and arterial calcification in ovariectomized rats
Authors: Park J.‐H. , Iemitsu M. , Maeda S. , Kitajima A. , Nosaka T. , Omi N.
Published: February 2008

Aim:  Loss of oestrogen synthesis capacity after menopause contributes to increases in arterial stiffness and calcification. Exercise training improves arterial stiffness and calcification. However, the mechanism of exercise training‐induced improvement of arterial stiffness and calcification remains unclear.

Method:  We examined the mechanism by using aortas of sham‐operated rats (sham control; SC), ovariectomized rats (OVX control; OC), OVX plus treatment with vitamin D3 plus nicotine (VDN) rats (OV sedentary; OVSe), which is an animal model of endothelial dysfunction and arterial calcification, and voluntary running wheel exercise for 8 weeks plus OVX plus VDN rats (OV exercise; OVEx).

Results:  The arterial tissue calcium and endothelin‐1 (ET‐1: a vasoconstrictor peptide and a potent regulator of arterial calcification) levels were significantly higher in OVSe rats compared with the SC and OC rats, whereas these levels in the OVEx rats were significantly lower than in the OVSe rats. Additionally, arterial expression of endothelial nitric oxide synthase (eNOS), which is an enzyme that produces nitric oxide (NO: a vasodilator substance), was reduced in OVSe rats. However, exercise training prevented the decrease in eNOS expression. Moreover, there was a significant positive correlation between arterial calcium level and arterial ET‐1 level.

Conclusion:  These findings suggest that exercise training‐induced improvement of ET‐1 and NO prevents the impairment of endothelial function after menopause in females, and this improvement may result in less arterial calcification.
Near‐infrared spectroscopy provides an index of blood flow and vasoconstriction in calf skeletal muscle during lower body negative pressure
Authors: Hachiya T. , Blaber A. P. , Saito M.
Published: February 2008

Aim:  Near‐infrared spectroscopy (NIRS) has been used previously for forearm blood flow estimation at rest and during exercise. In this study we applied NIRS to selectively monitor deep calf oxygenated haemoglobin (Hb) responses in order to estimate blood flow changes in the calf muscle during lower body negative pressure (LBNP). The purpose of this study was to test the hypothesis that changes in calf skeletal muscle oxygenated‐Hb, after the removal of superficial tissue responses, were related to blood flow changes during orthostatic stress, and to determine the efficacy of using NIRS measurements as an index of vasoconstriction.

Methods:  Twenty‐nine subjects participated in this study. All attempted a graded LBNP trial from baseline (0 mmHg) to −60 mmHg LBNP in 10 mmHg steps at 5‐min intervals. Calf blood flow changes were estimated by oxygenated‐Hb responses in relation to changes in mercury strain gauge plethysmography and muscle sympathetic nerve activity (MSNA).

Results:  Calf selective deep oxygenated‐Hb decreased continuously from −10 mmHg LBNP. Regression analysis showed that oxygenated‐Hb was significantly related to declines in plethysmography evaluations of blood flow [oxygenated‐Hb = (−1.57 ± 0.26) + (1.86 ± 0.49) plethysmography, r2 = 0.87 ± 0.09]. Changes in MSNA (total activity) were also inversely related to oxygenated‐Hb (slope < 0, P = 0.037; r2 = 0.52 ± 0.15).

Conclusion:  These results suggest that changes in selective deep calf oxygenated‐Hb can be utilized to estimate calf muscle blood flow changes that are most likely caused by vasoconstriction during graded LBNP.
Mathematical modelling of the calcium–left ventricular pressure relationship in the intact diabetic rat heart
Authors: Op Den Buijs J. , Ligeti L. , Ivanics T. , Miklós Z. , Van Der Vusse G. J. , Van Riel N. A. W.
Published: February 2008

Aim:  The objective was to characterize cross‐bridge kinetics from the cytoplasmic calcium ion concentration ([Ca2+]i) and the left ventricular pressure (LVP) in the early‐stage diabetic rat heart under baseline conditions and upon β‐adrenergic stimulation.

Methods:  Four weeks after the induction of diabetes in rats by the injection of streptozotocin, the hearts were perfused according to Langendorff, and [Ca2+]i was obtained by epifluorescence measurements using Indo‐1 AM. [Ca2+]i and LVP were measured simultaneously at a temporal resolution of 200 Hz. The input/output relationship between the Ca2+ and the pressure transients was described by a mathematical model representing the chemical binding of Ca2+ to troponin C on the actin myofilament (TnCA), and the subsequent cooperative force‐producing cross‐bridge formation of the Ca2+–TnCA complex with myosin. The kinetic parameters of this model were evaluated using a numerical optimization algorithm to fit the model equations to the experimental data. β‐adrenergic stimulation of the hearts with increasing doses of isoproterenol allowed quantification of the model parameters over an extended dynamic range, because isoproterenol administration increased developed pressure, heart rate, as well as [Ca2+]i amplitude in a dose‐dependent manner.

Results:  Model analysis of the experimental data indicates that β‐adrenergic stimulation of healthy hearts resulted in a decreased sensitivity of TnCA for Ca2+, increased rates of cross‐bridge cycling and decreased cooperativity. By contrast, the responses in cross‐bridge kinetic parameters to isoproterenol stimulation were blunted in the 4‐week diabetic heart.

Conclusion:  We conclude from our modelling results that myocardial cross‐bridge cycling is impaired at the early stage of diabetes.
Structural and functional evolution of gonadotropin‐releasing hormone in vertebrates
Authors: Okubo K. , Nagahama Y.
Published: February 2008

The neuropeptide gonadotropin‐releasing hormone (GnRH) has a central role in the neural control of vertebrate reproduction. This review describes an overview of what is currently known about GnRH in vertebrates in the context of its structural and functional evolution. A large body of evidence has demonstrated the existence of three paralogous genes for GnRH (GnRH1, GnRH2 and GnRH3) in the vertebrate lineage. They are most probably the products of whole‐genome duplications that occurred early in vertebrate evolution. Although GnRH3 has been identified only in teleosts, comparative genomic analyses indicated that GnRH3 has not arisen from a teleost‐specific genome duplication, but has been derived from an earlier genome duplication in an ancestral vertebrate, followed by its loss in the tetrapod lineage. A loss of other paralogous genes has also occurred independently in different vertebrate lineages, leading to species‐specific differences in the organization of the GnRH system. In addition to the GnRH3 gene, the GnRH2 gene has been deleted or silenced in certain mammalian species, while some teleosts seem to have lost the GnRH1 or GnRH3 gene. The duplicated GnRH genes have undergone subfunctionalization during the evolution of vertebrates; GnRH1 has become the major stimulator of gonadotropins and probably other pituitary hormones as well, whereas GnRH2 and GnRH3 would have functioned as neuromodulators, affecting reproductive behaviour. Conversely, in cases where a paralogous gene for GnRH has been lost, one of the remaining paralogues appears to have adopted its role.
Ventricular repolarization pattern under heart cooling in the rabbit
Authors: Azarov J. E. , Shmakov D. N. , Vityazev V. A. , Roshchevskaya I. M. , Arteyeva N. V. , Kharin S. N. , Roshchevsky M. P.
Published: February 2008

Aim:  Prolongation of ventricular repolarization is characteristic of myocardial cooling. In the present study, we investigated whether this prolongation is uniform or not throughout ventricular epicardium and how these hypothermia‐induced changes express in the body surface potential distribution.

Methods:  Epicardial and body surface potential mapping from 64 unipolar leads was carried out in 18 anaesthetized adult rabbits. Mild hypothermia documented by lowering the mediastinal and rectal temperature from 38 to 32 °C was elicited by perfusion of the mediastinum with cooled saline. Activation times, repolarization times and activation–recovery intervals were determined in each epicardial lead.

Results:  Baseline activation–recovery intervals distributed non‐uniformly on the ventricular epicardium, increasing progressively from the apex to the base and from the left ventricular (LV) sites to the right ventricular (RV) sites (P < 0.05), governing the repolarization sequence of ventricular epicardium. Heart cooling from 38 to 32 °C produced the heterogeneous prolongation of activation–recovery intervals which was more pronounced at the apex than at the base, and in the LV areas compared to the RV areas (P < 0.05). These nonuniform changes in local repolarization durations resulted in the development of base‐to‐apex repolarization sequence and inversion of the body surface potential distribution during the T wave.

Conclusion:  Thus, under cooling the rabbit heart from 38 to 32 °C, the nonuniform prolongation of local repolarization durations resulted in the reversal of ventricular epicardial repolarization sequence which, in turn, was responsible for the inversion in the body surface potential distribution during the T wave.
Effect of luminal Ca2+on the stability of coupled gating between ryanodine receptors from the rat heart
Authors: Gaburjakova J. , Gaburjakova M.
Published: February 2008

Aim: Two or more RYR2 channels reconstituted into a bilayer lipid membrane (BLM) can open and close either independently (single gating) or simultaneously (coupled gating). The coupled gating phenomenon has been suggested as an attractive candidate for a termination mechanism of Ca2+release from the sarcoplasmic reticulum, required for periodic contraction and relaxation of cardiac muscle.

Methods: Using the method of reconstitution of a channel into the BLM, we investigated the potential effect of luminal Ca2+on the stability of the interaction between coupled RYR2 channels isolated from the rat heart. We introduced a new parameter – the coupling stability – for each detected simultaneous opening and closing and further averaged values for experiments performed under identical conditions.

Results: We found that the coupling stability during simultaneous opening of RYR2 channels was significantly lower in comparison with the simultaneous closing under the same experimental conditions. Furthermore, high concentration of luminal Ca2+(53 mmol L−1) as well as the absence of luminal Ca2+noticeably destabilized functional coupling between coupled RYR2 channels during opening, in contrast to lower tested concentrations (8–20 mmol L−1).

Conclusions: We provide experimental evidence that the strength of interaction between coupled RYR2 channels depends on the functional state of the channels. Furthermore, we show, for the first time, the regulation role of luminal Ca2+in the inter‐RYR2 functional coupling in the rat heart.
Seabird life histories and climatic fluctuations: a phylogenetic‐comparative time series analysis of North Atlantic seabirds
Authors: Sandvik Hanno , Einar Erikstad Kjell
Published: February 2008

In the light of the predicted changes in climate as a consequence of global warming, it is a major concern how animal species will respond to altered meteorological and oceanographic conditions. Seabirds constitute a diverse group of marine top predators which have relatively low fecundity and high annual survival rates. In order to predict effects of climate change, it is a necessary precondition to first understand responses to naturally occurring climatic fluctuations. While the ecological effects of different large‐scale climatic phenomena have received much attention in the recent past, the factors determining the responses of seabirds are still little understood. We analyze more than a hundred previously published time series of seabird offspring production and adult survival rates in the North Atlantic in order to detect climatic signals in this data base. As our analyses are phylogenetic‐comparative, we are able to search for patterns across species. Using the correlation of these parameters with the North Atlantic Oscillation (NAO) as a measure of responsiveness to climatic variability, we find that effects of climate on either parameters considered are not more common than expected by chance. The magnitudes of the responsivenesses were entirely randomly distributed throughout the seabird phylogeny, but were not strongly related to the explanatory variables considered. However, some tendencies indicate that both life‐history traits and feeding ecology may influence how seabirds respond to climatic variability. An explanation of those patterns based on life‐history theory is given.
Large‐scale spatial variation in palm fruit abundance across a tropical moist forest estimated from high‐resolution aerial photographs
Authors: A. Jansen Patrick , A. Bohlman Stephanie , X. Garzon‐Lopez Carol , Olff Han , C. Muller‐Landau Helene , Joseph Wright S.
Published: February 2008

Fruit abundance is a critical factor in ecological studies of tropical forest animals and plants, but difficult to measure at large spatial scales. We tried to estimate spatial variation in fruit abundance on a relatively large spatial scale using low altitude, high‐resolution aerial photography. We measured fruit production for all 555 individuals of the arborescent palm Astrocaryum standleyanum across 25 ha of mapped tropical moist forest on Barro Colorado Island, Panama, by visually counting fruits from the ground. Simultaneously, we used high‐resolution aerial photographs to map sun‐exposed crowns of the palm across the same area, which were then linked to ground‐mapped stems. First, we verified that the fruit crop size of individual trees was positively associated with both crown presence on aerial photos and crown area visible on aerial photos. Then, we determined how well spatial variation in Astrocaryum fruit density across the study area was predicted by spatial densities of photo‐detected crowns and crown area compared to spatial densities of ground‐mapped stems and stem diameters. We found a positive association of fruit crop size with crown visibility on aerial photographs. Although representing just one third of all individuals in the study area, photo‐detected crowns represented 57% of all fruits produced. The spatial pattern of photo‐detected crowns was strongly correlated with the spatial pattern of fruit abundance based on direct fruit counts, and correctly showed the areas with the highest and lowest fruit abundances. The spatial density of photo‐detected crowns predicted spatial variation in fruit abundance equally well as did the spatial density of ground‐mapped stems. Photo‐detected crown area did not yield a better prediction. Our study indicates that remote sensing of crowns can be a reliable and cost‐effective method for estimating spatial variation in fruit abundance across large areas for highly distinctive canopy species. Our study is also among the few to provide empirical evidence for a positive relationship between crown exposure of forest trees and fruit production.
Is farther seed dispersal better? Spatial patterns of offspring mortality in three rainforest tree species with different dispersal abilities
Authors: Jansen Patrick A. , Bongers Frans , Van Der Meer Peter J.
Published: February 2008

The paradigm that tropical trees with farther seed dispersal experience lower offspring mortality is currently based on within‐species studies documenting higher survival of offspring located farther from conspecific adults and/or closer to light gaps. We determined whether the paradigm also holds among species by comparing spatial patterns of offspring mortality among three sympatric Neotropical rainforest tree species with the same seed dispersers but with different dispersal abilities. First, we assessed spatially non‐random mortality for each species by measuring spatial shifts of the population recruitment curve (PRC) with respect to conspecific adults and light gaps across three early life stages: dispersed seeds, young seedlings and old seedlings. Then, we determined whether PRC shifts were greater for the species with short dispersal distances than for the species with greater dispersal distances. We found that the PRC shifted away from conspecific adults consistently across life stages, but we found no consistent PRC shifts towards gaps, suggesting that mortality was related more to the proximity of conspecifics than to absence of light gaps. PRC shifts away from adults were greatest in the species with the lowest dispersal ability, supporting the paradigm. Differential PRC shifts caused the spatial distribution of offspring to become almost independent with respect to adult trees and gaps in all three species, despite large differences in seed dispersal distance among these species. Our results provide direct empirical support for the paradigm that among tropical trees, species with farther seed dispersal are less impacted by spatially non‐random mortality than are similar species with shorter dispersal distances. Thus, greater dispersal effectiveness merits extra investments of trees in seed dispersal ability, even at the cost of fecundity.
Connectance and parasite diet breadth in flea‐mammal webs
Authors: Mouillot David , Krasnov Boris R. , I. Shenbrot Georgy , Poulin Robert
Published: February 2008

The number of links in webs of species interactions, which lies at the heart of the biodiversity‐stability debate, has given rise to controversy during the last 20 yr. Studies exploring these web properties have mainly focused on symmetric webs where each species can potentially feed on any other species; asymmetric webs such as host‐parasite webs, where one set of species feed on another set of species, have been overlooked. However, food webs are incomplete without parasites and the study of parasite‐host sub‐web properties deserves attention. Here, using a large database involving 33 regional interaction webs between mammals and their flea parasites, we found a negative relationship between species richness and host‐parasite connectance. We suggest that some phylogenetic constraints on flea diet may explain our observed patterns because we found that parasite diet breadth, measured as host taxonomic diversity, was invariant along our host richness gradient. We found that the slope of the logarithmic relationship between the number of realized links and species richness is lower than slope values reported for food webs. We suggest that connectance may not respond to increasing species richness as rapidly in host‐parasite webs as in predator‐prey food webs due to stronger coevolutionary requirements.
Demography of alpine red squirrel populations in relation to fluctuations in seed crop size
Authors: A. Wauters Lucas , Githiru Mwangi , Bertolino Sandro , Molinari Ambrogio , Tosi Guido , Lens Luc
Published: February 2008

Vertebrate population dynamics, social organisation and space use often are closely associated with the distribution of critical resources, such as food. Tree squirrels are ideal models to study these relationships, since both key demographic parameters (reproduction, survival and dispersal) and spatio‐temporal variation in food supplies (measured as seed‐crop size) can be reliably estimated. In this paper we test the following two predictions underlying the association between annual food abundance and demography in six alpine red squirrel populations, both with and without time‐lag effects: 1) between‐season and between‐year fluctuations in survival rate, population density and increase parallel those in food availability; and 2) individuals follow a resource tracking strategy and increase in density mainly the year after a rich seed‐crop. Red squirrels occurred at higher densities in Scots pine forest, characterised by stable seed‐crops, than in Norway spruce with more abundant but more variable seed crops. Fluctuations in numbers were positively correlated with food availability, measured as annual conifer seed‐crop sizes. Overall, adult survival rates were higher than those of subadults, and survival substantially fluctuated between seasons and years. Autumn densities and rates of population increase (summer‐autumn) were strongly correlated with the same year's autumn seed‐crop, while correlations with the previous year's seed‐crop (time‐lag models) were either weak (population density) or absent (population increase). Results of this paper show that fluctuations in red squirrel densities in habitats with strong temporal variation in seed production are more closely linked with food availability than in more stable habitats. In addition, in the Alpine conifer forests squirrel population sizes, in autumn, increase in synchrony with food resources, eliminating the population lag normally present when resources are produced in pulses.
Population structure and migratory directions of Scandinavian bluethroats Luscinia svecica– a molecular, morphological and stable isotope analysis
Authors: Hellgren Olof , Bensch Staffan , A. Hobson Keith , Lindström Åke
Published: February 2008

Many species of birds show evidence of secondary contact zones and subspeciation in their Scandinavian distribution range, presumably resulting from different post‐glacial recolonization routes. We investigated whether this is the case also in the Scandinavian bluethroat Luscinia svecica, a species that has been suggested to consist of two separate populations: one SW‐migrating and long‐winged (L. s. gaetkei) breeding in southern Norway, and one shorter‐winged ESE‐migrating (L. s. svecica) in northern Scandinavia. We sampled males at eleven breeding sites from southern Norway to northernmost Sweden. There were no morphological differences or latitudinal trends within the sample, neither were there any genetic differences or latitudinal trends as measured by variation in AFLP and microsatellite markers. Stable isotope ratios of throat feathers moulted on the wintering grounds showed no, or possibly marginal differences between birds from southern Norway and northern Sweden. We also re‐measured old museum skins that in previous studies were classified as L. s.gaetkei, and found marginally longer wings in birds from the southern part of the Scandinavian breeding range. The difference, however, was much smaller than proposed in earlier studies. We conclude that there is no evidence of a genetic population structure among Scandinavian bluethroats that would suggest the presence of a zone of secondary contact. Finally we discuss whether the presumed subspecies gaetkei ever existed.
Consistent spatial patterns across biogeographic gradients in temperate reef fishes
Authors: Wellenreuther Maren , Syms Craig , Clements KendalL D.
Published: February 2008

Biogeographic gradients may facilitate divergent evolution between populations of the same species, leading to geographic variation and possibly reproductive isolation. Previous work has shown that New Zealand triplefin species (family Tripterygiidae) have diversified in habitat use, however, knowledge about the consistency of this pattern throughout their geographic range is lacking. Here we examine the spatial habitat associations of 15 New Zealand triplefin species at nine locations on a latitudinal gradient from 35°50′S to 46°70′S to establish whether distant populations differ in habitat use. Triplefin diversity and density varied between locations, as did habitat variables such as percentage cover of the substratum, onshore‐offshore location, microposition, depth and exposure. Canonical discriminant analysis identified specific species‐habitat combinations, and when habitat was statistically partialled from location, most species exhibited consistent habitat associations throughout their range. However, the density of a few species at some locations was lower or higher than expected given the habitat availability. This indicates that the habitat variables recorded were not the sole predictors of assemblage structure, and it is likely that factors influencing larval dispersal (e.g. the low salinity layer in Fiordland and geographic isolation of the Three Kings Islands) play an additional role in structuring assemblage composition. Together these results suggest that New Zealand triplefin species show strong and consistent habitat use across potential biogeographical barriers, but this pattern appears to be modified by variation in larval supply and survival. This indicates that species with broad geographic distributions do not necessarily show phenotypic variation between populations.
Integrating life history and physiology to understand latitudinal size variation in a damselfly
Authors: De Block Marjan , Slos Stefanie , Johansson Frank , Stoks Robby
Published: February 2008

Our understanding of latitudinal life history patterns may benefit by jointly considering age and mass at maturity and growth rate. Additional insight may be gained by exploring potential constraints through pushing growth rates to their maximum and scoring physiological cost‐related variables. Therefore, we reared animals of a univoltine Spanish and Belgian population and of a semivoltine Swedish population of the damselflyEnallagma cyathigerum(spanning a latitude gradient of ca 2350 km) in a common environment from the eggs until adult emergence and exposed them to a transient starvation period to induce compensatory growth. Besides age and mass at maturity and growth rate we also scored investment in energy storage (i.e. triglycerides) and immune function (i.e. total activity of phenoloxidase). At emergence, body mass was greater in Spain and Sweden and lower in Belgium, suggesting a genetic component for the U‐shaped latitudinal pattern that was found also in a previous study based on field‐collected adults. The mass difference between univoltine populations can be explained by the shorter development time in the Belgian population, and this despite a higher growth rate, a pattern consistent with undercompensating countergradient variation. In line with the assumed shorter growth seasons, Belgian and Swedish animals showed higher routine growth rates and compensatory growth after transient starvation. Despite a strong link with metabolic rates (as measured by oxygen consumption) populations with higher routine growth rates had no lower fat content and had higher immune function (i.e. immune function decreased from Sweden to Spain), which was unexpected. Rapid compensatory growth did, however, result in a lowered immune function. This may contribute to the absence of perfect compensating countergradient variation in the Belgian population and the lowest routine growth rates in the Spanish population. Our results underscore the importance of integrating key life historical with physiological traits for understanding latitudinal population differentiation.
Scale dependent diversity patterns in arboreal and terrestrial oribatid mite (Acari: Oribatida) communities
Authors: Lindo Zoë , N. Winchester Neville
Published: February 2008

In naturally fragmented, isolated, or patchily distributed habitats that contain non‐vagile organisms, we expect dispersal to be limited, and patterns of diversity to differ from similar, yet continuous habitats. We explored the alpha‐beta‐gamma relationship and community composition of oribatid mites (Acari: Oribatida) inhabiting spatially discrete canopy suspended soils, and compared the patterns of diversity with the continuous forest floor soils over two years. We explored dispersal limitation for oribatid mites in the canopy by using additive partitioning of species richness at multiple spatial scales. ANOSIM was used to demonstrate differences in oribatid mite community composition between the canopy and forest floor habitats over different sampling periods. Community composition of oribatid mites differed significantly between canopy and forest floor habitats, by season and yearly sampling period. Oribatid mite richness and abundance were positively correlated with substrate moisture content, particularly in the canopy. Richness and abundance of ground oribatid mites was greater in September than in June, a trend that is reversed in the canopy, suggesting canopy oribatid mite species may have altered life histories to take advantage of earlier moisture conditions. Alpha diversity of oribatid mites in the canopy was lower than the ground at all sampling levels, and not significantly different from a random distribution in either habitat. Beta diversity was greater than expected from a random distribution at the patch‐ and tree‐level in the canopy suggesting dispersal limitation associated with physical tree‐to‐tree dispersal barriers, and limited dispersal among patches within a tree. Beta diversity at the tree‐level was the largest contribution to overall species richness in both canopy and ground habitats, and was also greater than expected on the ground. These results suggest that factors other than physical dispersal barriers, such as aggregation, habitat availability, and environmental factors (moisture), may limit the distribution of species in both habitats.
1‐factorization of regular graphs by colour exchange
Authors: Cariolaro David
Published: February 2008

We present a new general theory that deals with the problem of determining a 1‐factorization of a graph using only the elementary technique of colour exchange. Our work is inspired by an old question of Vizing, who in [Cybernetics 3 (1965) 32–41] asked whether an optimal edge colouring of any multigraph G can always be obtained from an arbitrary edge colouring of G by repeatedly exchanging colours along bicoloured chains and suppressing empty colour classes. We conjecture that the answer to Vizing's question is affirmative. We apply our theory to the class of regular graphs of even order at most 10, proving the validity of this conjecture for this class of graphs. This yields an algorithm for finding a 1‐factorization of any 1‐factorizable graph of order at most 10. We also formulate two (stronger) conjectures and prove that they hold for the same class of graphs. Our method can be extended to graphs of larger order and to non‐regular graphs or multigraphs.