bluuebunny/crossref_metadata_2025 huggingface dataset:
Extra‐pair paternity in the strongly monogamous Wandering AlbatrossDiomedea exulanshas no apparent benefits for females
Authors: JOUVENTIN PIERRE , CHARMANTIER ANNE , DUBOIS MARIE‐PIERRE , JARNE PHILIPPE , BRIED JOËL
Published: September 2006

Although 92% of avian species are socially monogamous, extra‐pair copulation (EPC), resulting in extra‐pair paternity (EPP), is a common reproductive strategy in birds. Among seabirds, in which the rate of social monogamy reaches 100%, Procellariiformes (albatrosses and petrels) show low EPP rates, with the noticeable exception of the only albatross investigated in this regard, the Waved AlbatrossPhoebastria irrorata. This species, in which forced copulations are known to occur, showed a surprisingly high rate of EPP (25% of chicks). We investigate here EPP rates in another albatross species, the Wandering AlbatrossDiomedea exulans, subject to a demographic survey conducted for 38 years. We combined data on pair bonds with analysis of ten microsatellite loci and found that 10.7% of 75 chicks had an extra‐pair sire. Although there was some evidence for inbreeding avoidance, within‐pair and extra‐pair chicks showed similar levels of heterozygosity, and the incidence of EPP was independent of age, experience or past reproductive success. Hence, we found no evidence that females benefit from EPCs. Owing to the male‐biased sex ratio in adults, widowed and divorced males required more time to find a new mate (+28 and +72%, respectively) than did females. Combined with high sexual size dimorphism, this phenomenon might promote the forced copulations observed in this species. Our data therefore suggest that EPC is beneficial to unpaired males but occurs at random in females, consistent with the hypothesis that EPP results solely from forced EPCs. However, the importance of the latter for EPP and the part played by solitary males require further investigation.
‘Dad says I'm tied to a shooting star!’ Grounding (research on) British expatriate belonging
Authors: Walsh Katie
Published: September 2006

This paper analyses one British woman's everyday practices of belonging as she negotiates expatriate life in Dubai, United Arab Emirates. In doing so, it responds to widespread calls to ground research on processes of transnationalism and diaspora by drawing on 18 months of ethnographic research and adopting a three‐stranded analytical framework to reflect on the significance of domesticity, intimacy and foreignness in expatriate belonging. The author focuses on a single research subject to draw attention to a particular British expatriate experience otherwise neglected in migration research and the paper resonates with theoretical literatures aiming to challenge the binary divisions of geographies of belonging, including attachment/detachment.
Urban parks as shared spaces? The utility of alert distances as indicators of avian tolerance of humans in Stirling, Scotland
Authors: O’Neal Campbell Michael
Published: September 2006

Urban avian foraging is strongly affected by approaching people. Avian alert distances, the instant of a bird's appraisal of human intrusion, have not been studied in a comparative mode for passerines, despite their prominent ecological importance in parks. Alert distances for 13 passerines were examined in parks in Stirling, Scotland, using an innovative approach emphasizing human behaviour and periods between alert and flight distances, termed alert periods. Larger species were less tolerant of humans, although attracted to human wastes. Alert distances also varied according to vegetation variation. Park design may use alert distances to plan vegetation layout as well as reduce disturbing human behaviour.
Geography and Benedict XVI
Authors: Korf Benedikt
Published: September 2006

Love is indeed ‘ecstasy’, not in the sense of a moment of intoxication, but rather as a journey, an ongoing exodus out of the closed inward‐looking self towards its liberation through self‐giving, and thus towards authentic self‐discovery and indeed the discovery of God. (Benedict XVI, Encyclical letter Deus Caritas Est)
Percutaneous Endocardial and Epicardial Ablation of Hypotensive Ventricular Tachycardia with Percutaneous Left Ventricular Assist in the Electrophysiology Laboratory
Authors: FRIEDMAN PAUL A. , MUNGER THOMAS M. , TORRES NORMAN , RIHAL CHARANJIT
Published: September 2006

Ventricular tachycardia (VT) in the setting of structural heart disease is challenging to treat with percutaneous catheter ablation due to the presence of complex substrate, multiple morphologies, hemodynamic instability, and epicardial circuits. When substrate‐based approaches fail, however, it may be impossible to map and ablate hemodynamically unstable arrhythmias. We describe a novel approach to endocardial and epicardial mapping and ablation of hypotensive VT using a percutaneous left ventricular assist device in the electrophysiology laboratory, permitting near‐surgical access to cardiac structures.
Progress of Untreated Massive Cardiac Echinococcosis—Echocardiographic Follow‐Up
Authors: Soydinc Serdar , Davutoglu Vedat , Oylumlu Muhammed
Published: September 2006

A 56‐year‐old man was admitted with chest pain and dyspnea. Echocardiographic evaluation revealed a giant cystic cardiac mass with multiple loculations at interventricular septum extended to inferoposterior region protruding inside the cavity. The patient refused surgical therapy. His complaints persisted without significant changes after 5 months. Second echocardiographic evaluation revealed conjugation of previous multiple cyst to gigantic intramyocardial cyst and minimal pericardial effusion. We intend to illustrate herein an unusual echocardiographic appearance and progress of an untreated massive “cardiac echinococcosis.” If cardiac hydatid cyst is left untreated it may transform to large cavity with a high risk of rupture.
Cor Triatriatum Sinister: Assessment by Live/Real Time Three‐Dimensional Transthoracic Echocardiography
Authors: Patel Vinod , Nanda Navin C. , Arellano Iliana , Yelamanchili Pridhvi , Rajdev Sanjay , Baysan Oben
Published: September 2006

We report a 49‐year‐old morbidly obese female with a poor acoustic window in whom live/real time three‐dimensional transthoracic echocardiography was able to make a confident diagnosis of cor triatriatum sinister. En face views of the membrane facilitated accurate assessment of the size and shape of the large nonobstructing opening in the membrane. Maximum dimensions of the opening were 3.06 × 1.03 cm and area was 2.3 cm2.
Protist Genetic Diversity in the Acidic Hydrothermal Environments of Lassen Volcanic National Park, USA
Authors: BROWN PATRICIA B. , WOLFE GORDON V.
Published: September 2006

ABSTRACT. We examined eukaryote genetic diversity in the hydrothermal environments of Lassen Volcanic National Park (LVNP), Northern California. We sampled hydrothermal areas of the Bumpass Hell, Sulfur Works, Devil's Kitchen, and Boiling Springs Lake sites, all of which included diverse acidic pools, mud pots, and streams with visible algal mats and biofilms. Temperatures varied from 15 to 85°C and pH from 1.7 to 5.8. DNA extraction methods compared by denaturing gradient gel electrophoresis fingerprinting exhibited similar patterns, and showed limited diversity of eukaryotic small subunit (SSU) rRNA genes compared with prokaryotes. We successfully amplified eukaryotic SSU rRNA genes from most environments up to 68°C. Cloned rDNA sequences reveal acidophilic protists dominate eukaryotes in LVNP hydrothermal environments. Most sites showed phototrophic assemblages dominated by chlorophytes and stramenopiles (diatoms and chrysophytes). Heterotrophic taxa, though less abundant, included diverse alveolates (ciliates), amoebae, and flagellates. Fungi were also found at most sites, and metazoans (hexapods, nematodes, platyhelminths) were sometimes detected in less acidic environments, especially in algal mats. While many cloned rDNA sequences showed 95%–99% identity to known acidophilic isolates or environmental clones from other acidic sites (Rio Tinto), sequence diversity generally declined both with decreasing pH and increasing temperature, and both were controlling physical variables on the abundance and distribution of organisms at our sites. However, a pool at 68°C with pH 1.7 yielded the greatest number of distinct sequences. While some were likely contaminants from nearby cooler sites, we suggest that Lassen's acidic hydrothermal features may harbor novel protists.
Pelagostrobilidium wilberti n. sp. (Oligotrichea, Choreotrichida): Morphology and Morphogenesis
Authors: KÜPPERS GABRIELA C. , LOPRETTO ESTELA C. , CLAPS MARÍA C.
Published: September 2006

ABSTRACT. Morphology, infraciliature, morphogenetic features, and some ecological data for Pelagostrobilidium wilberti n. sp. are described. This new species was collected from a temporary pond in Magdalena, Buenos Aires province, Argentina, which was sampled monthly from August 2003 to July 2005. The species was found in autumn and winter. Observations were made in vivo and after staining with protargol. Pelagostrobilidium wilberti n. sp. measures 63–84 × 42–49 μm in vivo and is conical in shape, with a posterior spine‐like cytoplasmic process. It possesses 6 somatic kineties, with kinety 2 sinistrally curved and shorter than the others. The oral apparatus is composed of 25–32 external and two internal membranelles. The macronucleus is horseshoe‐shaped and located beneath the oral apparatus; two or three spherical micronuclei lie dorsally. There is a posterior contractile vacuole. Morphogenesis is hypo‐apokinetal and begins dorsally between the curved kinety 2 and kinety 3. After the discovery of this new species, the diagnosis of the genus Pelagostrobilidium was amended.
Cytopathogenicity of Balamuthia mandrillaris, an Opportunistic Causative Agent of Granulomatous Amebic Encephalitis
Authors: KIDERLEN ALBRECHT F. , TATA PHIROZE S. , ÖZEL MUHSIN , LAUBE ULRIKE , RADAM ELKE , SCHÄFER HUBERT
Published: September 2006

ABSTRACT. Balamuthia mandrillaris is a free‐living ameba and an opportunistic agent of lethal granulomatous amebic encephalitis in humans and other mammals. Balamuthia mandrillaris is highly cytopathic but, in contrast to the related Acanthamoeba, does not feed on bacteria and seems to feed only on eukaryotic cells instead. Most likely, the cytopathogenicity of B. mandrillaris is inseparable from its infectivity and pathogenicity. To better understand the mechanisms of B. mandrillaris cytopathogenicity, an assay for measuring amebic cytolytic activity was adapted that is based on the release of a reporter enzyme by damaged target cells. The ameba is shown to lyse murine mastocytoma cells very efficiently in a time‐ and dose‐related manner. Furthermore, experiments involving semipermeable membranes and phagocytosis inhibitors indicate that the cytolytic activity of B. mandrillaris is essentially cell contact‐dependent. Standard and fluorescence light microscopy, as well as scanning and transmission electron microscopy support and extend these findings at the ultrastructural level.
Frequency‐doubling technology: searching for the optimum diagnostic criteria for glaucoma
Authors: Ferreras Antonio , Larrosa José M. , Polo Vicente , Pajarín Ana B. , Mayoral Francesca , Honrubia Francisco M.
Published: September 2006

Purpose:  To determine the diagnostic criteria of perimetry using frequency‐doubling technology (FDT) with the best possible sensitivity−specificity balance for glaucoma diagnosis.

Methods:  A total of 92 healthy control subjects and 110 patients with varying degrees of glaucomatous visual field loss on standard automated perimetry (SAP) were used to obtain the best diagnostic criterion for the disease, by using screening C‐20‐1 and threshold C‐20 strategies from original FDT perimetry. Another prospective sample of 52 normal eyes and 64 glaucoma eyes was used to test how well this optimum criterion performs in other populations. Receiver operating characteristic (ROC) curves were plotted for the number of altered points at each level of probability for the C‐20‐1 and threshold C‐20 modes. In addition, ROC curves were calculated for the global indices of the threshold C‐20 strategy.

Results:  The best criterion for the C‐20‐1 strategy is the presence of one or more altered points with p < 1% (57.81% sensitivity and 100% specificity). The optimum criteria for glaucoma diagnosis for the threshold C‐20 strategy are the presence of five or more altered points with p < 5% and/or two or more altered points with p < 2% and/or at least one altered point with p < 1% at any location (79.68% sensitivity and 94.2% specificity).

Conclusions:  By using the C‐20‐1 strategy, a p < 1% defect anywhere showed 100% specificity with the lowest test duration. The criteria proposed for the threshold C‐20 algorithm presented a good sensitivity−specificity balance. The threshold C‐20 test provides higher sensitivity than the C‐20‐1 strategy but takes about five times longer to perform.
Intraocular lens power calculation for combined cataract surgery, vitrectomy and peeling of epiretinal membranes for macular oedema
Authors: Kovács Illés , Ferencz Mária , Nemes János , Somfai Gábor , Salacz György , Récsán Zsuzsa
Published: September 2006

Purpose:  This study aimed to compare preoperatively calculated and postoperatively achieved refraction following phacoemulsification and intraocular lens (IOL) implantation combined with pars plana vitrectomy with internal limiting membrane or epiretinal membrane removal.

Methods:
  Twelve eyes of 12 patients who underwent a combined procedure were enrolled in this study. Ultrasound axial length and macular thickness (optical coherence tomography, OCT) measurements were performed pre‐ and postoperatively. Intraocular lens power was calculated with the SRK/T formula and the planned refraction was compared with results of postoperative automatic refractometry. Comparisons between IOL calculations using the measured axial length and calculations using an adjusted axial length (by adding the macular thickness measured on OCT to the ultrasound axial length) were also performed.

Results:  Axial length increased (p = 0.02), whereas macular thickness decreased (p = 0.002). The planned refraction was 0.63 ± 0.38 dioptres, whereas the postoperative refraction error was − 0.16 ± 0.48 D (p = 0.02), with a mean difference of − 0.79 ± 0.24 D. During case‐to‐case comparisons, differences were observed between IOL calculations using the measured axial length and calculations using an adjusted axial length (0.63 ± 0.38 D versus 0.13 ± 0.48 D, p = 0.005). Correlation analysis showed a significant relationship between the ‘adjusted planned’ and the measured postoperative ametropia (r = 0.93, p < 0.001).

Conclusions:  The observed myopic shift due to erroneous IOL calculation results from underestimation of the axial length due to a thicker macula and calls for preoperative adjustment of ultrasound axial length when biometry is performed by this method.
Visually significant persistent outer retinal fluid following closure of a macular hole
Authors: Sears Katharine S. , Bhola Ronnie M. , Winder Stephen
Published: September 2006

Purpose:  We report two cases of persistent outer retinal fluid defects following macular hole surgery.

Methods:
  Twenty‐eight consecutive patients who underwent macular hole surgery performed by a single surgeon were examined pre‐ and postoperatively using slit‐lamp biomicroscopy and optical coherence tomography (OCT).

Results:  Two patients from this series were identified by OCT as having persistent outer retinal fluid defects after macular hole surgery, despite closure of the holes on biomicroscopy. One patient had only a small defect present at 6 weeks, with very good visual improvement, which was later shown to have resolved. The second had a large persistent defect and no postoperative improvement in vision despite the eventual resolution of the fluid 17 months later.

Conclusions:  Large pockets of persistent outer retinal fluid defects as shown on OCT may reduce final visual acuity in patients following macular hole surgery.
Current treatment modalities for exudative retinal hamartomas secondary to tuberous sclerosis: review of the literature
Authors: Mennel Stefan , Meyer Carsten H. , Peter Silvia , Schmidt Jörg C. , Kroll Peter
Published: September 2006

Background:  Retinal hamartoma is a common finding in tuberous sclerosis, but the symptomatic changes of this lesion have rarely been described. This evidence‐based review evaluated the incidence of symptomatic retinal hamartoma and compared possible treatment modalities.

Methods:
  We carried out a review of the literature using MEDLINE. Older publications not listed in MEDLINE were obtained from the reference list of currently published papers.

Results:  Three observational case series with a follow‐up of up to 34 years included 93 patients and reported progression from a flat to a more elevated lesion without visual symptoms in nine patients (9.7%). Additional symptomatic changes were described in 11 case reports published over a period of three decades. The symptomatic alterations were caused by an enlarged tumour with leakage, macular oedema, accumulating lipoid exudates, serous retinal detachment (n = 8/11) and vitreous haemorrhage (n = 4/11). Most symptomatic cases involved a retinal hamartoma type 1 (n = 6/8). Spontaneous resolution of symptomatic exudative hamartomas occurred in three patients within 4 weeks, although a delayed resorption of subretinal fluid caused permanent visual impairment in one patient. Investigational reports described a slow resorption of subretinal fluid after argon laser photocoagulation (n = 2), although recurrent laser applications induced choroidal neovascularization and destruction of the neurosensory retina (n = 1). A vitrectomy was used to remove a vitreous haemorrhage in another reported patient. In one case, complete resorption of subretinal fluid and an increase in visual acuity was observed within 2 weeks after a single treatment with photodynamic therapy (PDT). No complications were noted during a follow‐up of 4 years.

Conclusions:  Symptomatic changes are very rare in retinal hamartomas secondary to tuberous sclerosis. Spontaneous resolution of subretinal fluid may occur within 4 weeks. If a macular oedema with increasing lipoid exudates persists over a period of 6 weeks, treatment should be considered. Although previous reports demonstrated possible visual stabilization after argon laser photocoagulation, vision‐threatening complications can occur. Current treatment strategies may include PDT based on favourable anatomical and functional results.
In vivo β‐defensin gene expression in rat gingival epithelium in response to Actinobacillus actinomycetemcomitans infection
Authors: Kurland A. R. , Schreiner H. , Diamond G.
Published: September 2006

Background and Objective:  Human β‐defensins have been identified in the oral cavity and are predicted to play a role in the defense against pathogenic bacteria. Homologous rat β‐defensins (RBDs) have been identified, but their expression in the oral cavity has not been examined. Therefore, the aim of this study was to investigate the expression of innate immune mediators in the rat gingival epithelium.

Material and Methods:  Rats were pretreated with antibiotics to depress the normal oral flora, followed by the introduction of Actinobacillus actinomycetemcomitans in their food to allow colonization and the development of periodontal disease. At various time points, animals were killed and the gingival epithelium was extracted. Semiquantitative reverse transcription–polymerase chain reaction was performed to measure RBD and Toll‐like receptor (TLR) mRNA levels.

Results:  Three β‐defensins (RBD‐1, ‐2 and ‐5) and two TLRs (TLR‐3 and ‐4) are expressed in normal rat gingival epithelium. After the introduction of A. actinomycetemcomitans, RBD‐1 and RBD‐2 mRNA levels increased for the first week followed by a return to basal levels. No change in TLR mRNA levels was observed.

Conclusion:  The rat model provides a good system for experimental analysis of the innate immune response to periopathogenic bacteria in the oral cavity, as well as the potential role of β‐defensins in the host response to colonization.
Recolonisation and distribution of spiders and carabids in cereal fields after spring sowing
Authors: Öberg S. , Ekbom B.
Published: September 2006

Generalist predators are important for pest suppression during pest establishment because they may occur in the crop before and during pest arrival. However, different crop management practices can have a negative effect on predator populations. If so, there is a need for recolonisation by the predators to the crop fields. An important pest in Sweden is the bird cherry‐oat aphid, Rhopalosiphum padi, which migrates to cereal fields in spring. In turn, many cereal fields are spring sown and thus are disturbed by harrowing and sowing a short time before aphid arrival. In this study, three different questions about the populations of spiders and carabids in spring cereal crops were asked. First, does sowing in spring have a negative effect on the predators present in the fields? Second, if sowing has a negative effect on predator populations, do they recolonise the fields before pest arrival? Third, how are the predators distributed in the fields? We found that most carabids and most lycosid spiders were not affected by sowing and were distributed uniformly in the fields after sowing. Most linyphiid spiders were negatively affected by sowing, but then they recolonised the fields and were uniformly distributed in the fields after recolonisation. Thus, many spiders and carabids are present in the fields after sowing in spring and have the opportunity to suppress aphids during their establishment phase, which in turn may prevent a possible outbreak.
Radiative pressure feedback by a quasar in a galactic bulge
Authors: Fabian A. C. , Celotti A. , Erlund M. C.
Published: September 2006

We show that Eddington-limited black hole luminosities can be sufficient to deplete a galaxy bulge of gas through radiation pressure, when the ionization state of the gas and the presence of dust are properly taken into account. Once feedback starts to be effective it can consistently drive all the gas out of the whole galaxy. We estimate the amount by which the effect of radiation pressure on dusty gas boosts the mass involved in the Eddington limit, and discuss the expected column density at which the gas is ejected. An example is shown of the predicted observed nuclear spectrum of the system at the end of an early, obscured phase of growth when the remaining column density NH∼ 1024f cm−2, where f is the gas fraction in the bulge.
INFLUENCE OF FLAVORING ON THE VISCOELASTIC PROPERTIES OF STARCH GELS DURING GELATION AND LONG‐TIME RETROGRADATION
Authors: REPARET J.M. , MOINE F. , ARVISENET G. , LE BAIL P. , CAYOT N.
Published: September 2006

The effect of three different aroma compounds on the texture of starch dispersions during gelation and retrogradation was studied. Oscillatory measurements were used to follow gelation and to check the structure of the starch dispersions after retrogradation up to 28 days.

Rheological tests did not indicate any effect of the presence of any of the aroma compounds on the mechanism of gelation. During long‐time retrogradation, some added aroma compound did. We assume that this is a consequence of the ability of aroma compounds to form a complex or to show another type of interaction with starch molecules like entrapment in the amorphous regions of starch. Linalool is known to form complexes with amylase, but did not induce texture modifications, probably because, in our experiments, the added amount of this compound was too low. Isoamyl acetate, which according to literature interacts with amylopectin, exhibited a weak effect after 3 or 4 weeks, depending on the amount added. Octanal also increased gel stiffness after 3 weeks. This phenomenon is consistent with the observation that this aroma compound can form complexes with starch as demonstrated by X‐ray diffraction in this study.
INSTRUMENTAL METHODS TO CHARACTERIZE NONORAL TEXTURE OF DULCE DE LECHE
Authors: ARES GASTÓN , GIMÉNEZ ANA , GÁMBARO ADRIANA
Published: September 2006

Three different instrumental texture methods (vane yield stress determination, forward extrusion and penetration tests) were used to characterize nonoral texture of 13 commercial samples of dulce de leche, a type of sweetened condensed milk. Two sensory nonoral texture attributes (hardness and ropiness) were evaluated by a panel of 11 assessors, trained in descriptive analysis of dairy product's texture. All the studied instrumental methods showed high reproducibility and high discriminating ability between samples. Those instrumental parameters that are related to the firmness of dulce de leche (yield stress, extrusion force, hardness, modulus and adhesiveness) were highly correlated to sensory hardness. No instrumental parameter was able to reflect the sensory ropiness of the samples. From all the instrumental methods used to characterize the nonoral texture of dulce de leche, yield stress seems the most appropriate to be used in quality control programs, because it showed the highest discriminating ability and it has the advantage of being a quick and direct method.
EVALUATION OF ARTIFICIAL NEURAL NETWORKS FOR PINEAPPLE GRADING
Authors: BOONMUNG SUWANEE , CHOMTEE BOONORM , KANLAYASIRI KANNACHAI
Published: September 2006

The objective of this study is to evaluate resonant frequency, firmness and soluble solids for pineapple classification using artificial neural networks (ANNs) as the analytical tool. A sample of 149 pineapples was classified based on their internal qualities into five classes: unripe, partially ripe, ripe, partially overripe and completely overripe. The developed ANN model successfully classified pineapples into merely three classes as unripe, ripe and completely overripe. The most effective model was obtained when both resonant frequency and soluble solids were included in the model. The classification accuracy was more than 83% for all three classes.
PSYCHORHEOLOGY OF TARTAR SAUCE
Authors: ŠTERN P. , PANOVSKÁ Z. , POKORNÝ J.
Published: September 2006

Two series of tartar sauces were tested, each consisting of 10 samples, measured at 15, 20 and 25C. The yield value, apparent viscosity and thixotropy were determined using a rotational rheometer. The sensory profile and texture acceptability were determined according to international standards. Rheological parameters were significantly influenced by temperature while sensory characteristics were not affected by the temperature, except hedonic characteristcs. Rheological parameters were interrelated with high values of correlation coefficients. Statistically significant linear relations were observed between rheological and sensory data, but correlation coefficients were lower. Sensory texture acceptability had a great effect on the flavor acceptability. The sensory texture and flavor could be predicted with a fair degree of reliability using rheometry.
INVESTIGATION OF THE MECHANICS OF SINGLE TOMATO FRUIT CELLS
Authors: WANG C.X. , PRITCHARD J. , THOMAS C.R.
Published: September 2006

The mechanical behavior of single tomato fruit cells has been characterized using high strain‐rate microcompression testing. Single cells isolated by gentle washing from inner pericarp tissue were compressed to a wide range of deformations at a speed of 1500 µm/s, and then released. The cells were larger than any tested previously by microcompression, and had very low initial turgor. Force‐deformation data were modeled to find cell wall material properties, assuming water loss during compression could be neglected because of fast compression. Repeat compression‐release experiments were conducted to discover when cell deformation was no longer recoverable upon release. Cells from three commercially grown tomatoes were elastic to deformations of just over 11%. The elastic moduli of the cell walls were found by modeling to be 30 to 80 MPa, significantly lower than suspension‐cultured cell walls. The cell walls yielded at about 2% wall strain. High‐speed compression testing is a powerful tool for studying low turgor cells, such as those found during ripening.
Ovarian hormone status and skeletal muscle inflammation during recovery from disuse in rats
Authors: McClung J. M. , Davis J. M. , Carson J. A.
Published: September 2006

Resumption of normal muscle loading after a period of disuse initiates cellular processes related to mass accretion. The renewed loading also induces a significant amount of muscle damage and subsequent inflammation. Ovarian hormone depletion delays atrophied myofibre mass recovery. Ovarian hormones are also global regulators of immune system function. The purpose of this study was to determine whether ovarian hormone depletion‐induced deficits in myofibre regrowth after disuse atrophy are related to the induction of muscle damage and the associated inflammatory response. We hypothesized that soleus muscle immune cell infiltration and inflammatory gene expression would be both accentuated and prolonged in ovarian hormone‐depleted rats during the first week of recovery from disuse atrophy. Intact and ovariectomized (OVX) female rats were subjected to hindlimb suspension for 10 days and then returned to normal ambulation for a recovery period, the rats were killed and the soleus muscle removed for analysis. Although reloading increased both circulating creatine kinase and myofibre membrane disruption, there was no effect of ovarian hormones on these processes during recovery. Muscle neutrophil concentration was increased above baseline regardless of hormone status at days 1 and 3 of recovery; however, this increase was 43% greater at day 3 in the OVX group. Muscle ED1+ and ED2+ macrophage concentrations were increased during recovery in both groups. However, macropage concentrations remained elevated at day 7 of recovery in the OVX group, whereas they returned to control levels in the intact group. Cyclo‐oxygenase‐2, interleukin‐6 and interleukin‐1β muscle mRNA expression increased similarly during recovery, regardless of ovarian hormone status. These results demonstrate that the initial myofibre damage and inflammatory gene expression induced during muscle recovery from disuse atrophy are independent of ovarian hormone status.
Prior heavy exercise elevates pyruvate dehydrogenase activity and speeds O2 uptake kinetics during subsequent moderate‐intensity exercise in healthy young adults
Authors: Gurd B. J. , Peters S. J. , Heigenhauser G. J. F. , LeBlanc P. J. , Doherty T. J. , Paterson D. H. , Kowalchuk J. M.
Published: September 2006

The adaptation of pulmonary oxygen uptake during the transition to moderate‐intensity exercise (Mod) is faster following a prior bout of heavy‐intensity exercise. In the present study we examined the activation of pyruvate dehydrogenase (PDHa) during Mod both with and without prior heavy‐intensity exercise. Subjects (n= 9) performed a Mod1–heavy‐intensity–Mod2 exercise protocol preceded by 20 W baseline. Breath‐by‐breath kinetics and near‐infrared spectroscopy‐derived muscle oxygenation were measured continuously, and muscle biopsy samples were taken at specific times during the transition to Mod. In Mod1, PDHa increased from baseline (1.08 ± 0.2 mmol min−1 (kg wet wt)−1) to 30 s (2.05 ± 0.2 mmol min−1 (kg wet wt)−1), with no additional change at 6 min exercise (2.07 ± 0.3 mmol min−1 (kg wet wt)−1). In Mod2, PDHa was already elevated at baseline (1.88 ± 0.3 mmol min−1 (kg wet wt)−1) and was greater than in Mod1, and did not change at 30 s (1.96 ± 0.2 mmol min−1 (kg wet wt)−1) but increased at 6 min exercise (2.70 ± 0.3 mmol min−1 (kg wet wt)−1). The time constant of was lower in Mod2 (19 ± 2 s) than Mod1 (24 ± 3 s). Phosphocreatine (PCr) breakdown from baseline to 30 s was greater (P < 0.05) in Mod1 (13.6 ± 6.7 mmol (kg dry wt)−1) than Mod2 (6.5 ± 6.2 mmol (kg dry wt)−1) but total PCr breakdown was similar between conditions (Mod1, 14.8 ± 7.4 mmol (kg dry wt)−1; Mod2, 20.1 ± 8.0 mmol (kg dry wt)−1). Both oxyhaemoglobin and total haemoglobin were elevated prior to and throughout Mod2 compared with Mod1. In conclusion, the greater PDHa at baseline prior to Mod2 compared with Mod1 may have contributed in part to the faster kinetics in Mod2. That oxyhaemoglobin and total haemoglobin were elevated prior to Mod2 suggests that greater muscle perfusion may also have contributed to the observed faster kinetics. These findings are consistent with metabolic inertia, via delayed activation of PDH, in part limiting the adaptation of pulmonary and muscle O2 consumption during the normal transition to exercise.
Downregulation of tonic GABA currents following epileptogenic stimulation of rat hippocampal cultures
Authors: Qi Jin‐shun , Yao Jun , Fang Cheng , Luscher Bernhard , Chen Gong
Published: September 2006

Deficits in GABAergic inhibitory transmission are a hallmark of temporal lobe epilepsy and have been replicated in animal and tissue culture models of epilepsy. GABAergic inhibition comprises phasic and tonic inhibition that is mediated by synaptic and extrasynaptic GABAA receptors, respectively. We have recently demonstrated that chronic stimulation with cyclothiazide (CTZ) or kainic acid (KA) induces robust epileptiform activity in hippocampal neurons both in vitro and in vivo. Here, we report a downregulation of tonic GABA inhibition after chronic epileptogenic stimulation of rat hippocampal cultures. Chronic pretreatment of hippocampal neurons with CTZ or KA resulted in a marked reduction in GABAergic inhibition, as shown by a significant decrease in whole‐cell GABA currents and in the frequency of miniature inhibitory postsynaptic currents (mIPSCs). Interestingly, synaptically localized GABAA receptors remained relatively stable, as evidenced by the unaltered amplitude of mIPSCs, as well as the unchanged punctate immunoreactivity of γ2 subunit‐containing postsynaptic GABAA receptors. In contrast, tonic GABA currents, assessed either by a GABAA receptor antagonist bicuculline or a selective extrasynaptic GABAA receptor agonist THIP, were significantly reduced following epileptogenic stimulation. These results reveal a novel form of neural plasticity, that epileptogenic stimulation can selectively downregulate extrasynaptic GABAA receptors while leaving synaptic GABAA receptors unchanged. Thus, in addition to synaptic alteration of GABAergic transmission, regulation of tonic inhibition may also play an important role during epileptogenesis.
Thyrotropin‐releasing hormone increases GABA release in rat hippocampus
Authors: Deng Pan‐Yue , Porter James E. , Shin Hee‐Sup , Lei Saobo
Published: September 2006

Thyrotropin‐releasing hormone (TRH) is a tripeptide that is widely distributed in the brain including the hippocampus where TRH receptors are also expressed. TRH has anti‐epileptic effects and regulates arousal, sleep, cognition, locomotion and mood. However, the cellular mechanisms underlying such effects remain to be determined. We examined the effects of TRH on GABAergic transmission in the hippocampus and found that TRH increased the frequency of GABAA receptor‐mediated spontaneous IPSCs in each region of the hippocampus but had no effects on miniature IPSCs or evoked IPSCs. TRH increased the action potential firing frequency recorded from GABAergic interneurons in CA1 stratum radiatum and induced membrane depolarization suggesting that TRH increases the excitability of interneurons to facilitate GABA release. TRH‐induced inward current had a reversal potential close to the K+ reversal potential suggesting that TRH inhibits resting K+ channels. The involved K+ channels were sensitive to Ba2+ but resistant to other classical K+ channel blockers, suggesting that TRH inhibits the two‐pore domain K+ channels. Because the effects of TRH were mediated via Gαq/11, but were independent of its known downstream effectors, a direct coupling may exist between Gαq/11 and K+ channels. Inhibition of the function of dynamin slowed the desensitization of TRH responses. TRH inhibited seizure activity induced by Mg2+ deprivation, but not that generated by picrotoxin, suggesting that TRH‐mediated increase in GABA release contributes to its anti‐epileptic effects. Our results demonstrate a novel mechanism to explain some of the hippocampal actions of TRH.
TRP channels and lipids: from Drosophila to mammalian physiology
Authors: Hardie Roger C.
Published: September 2006

The transient receptor potential (TRP) ion channel family was the last major ion channel family to be discovered. The prototypical member (dTRP) was identified by a forward genetic approach in Drosophila, where it represents the transduction channel in the photoreceptors, activated downstream of a Gq‐coupled PLC. In the meantime 29 vertebrate TRP isoforms are recognized, distributed amongst seven subfamilies (TRPC, TRPV, TRPM, TRPML, TRPP, TRPA, TRPN). They subserve a wide range of functions throughout the body, most notably, though by no means exclusively, in sensory transduction and in vascular smooth muscle. However, their precise physiological roles and mechanism of activation and regulation are still only gradually being revealed. Most TRP channels are subject to multiple modes of regulation, but a common theme amongst the TRPC/V/M subfamilies is their regulation by lipid messengers. Genetic evidence supports an excitatory role of diacylglycerol (DAG) for the dTRP's, although curiously only DAG metabolites (PUFAs) have been found to activate the Drosophila channels. TRPC2,3,6 and 7 are widely accepted as DAG‐activated channels, although TRPC3 can also be regulated via a store‐operated mechanism. More recently PIP2 has been shown to be required for activity of TRPV5, TRPM4,5,7 and 8, whilst it may inhibit TRPV1 and the dTRPs. Although compelling evidence for a direct interaction of DAG with the TRPC channels is lacking, mutagenesis studies have identified putative PIP2‐interacting domains in the C‐termini of several TRPV and TRPM channels.
Dynamic Behavior and Stability of a Rotor Under Base Excitation
Authors: Duchemin M. , Berlioz A. , Ferraris G.
Published: September 2006

The dynamic behavior of flexible rotor systems subjected to base excitation (support movements) is investigated theoretically and experimentally. The study focuses on behavior in bending near the critical speeds of rotation. A mathematical model is developed to calculate the kinetic energy and the strain energy. The equations of motion are derived using Lagrange equations and the Rayleigh-Ritz method is used to study the basic phenomena on simple systems. Also, the method of multiple scales is applied to study stability when the system mounting is subjected to a sinusoidal rotation. An experimental setup is used to validate the presented results.
Numerical Modeling of Head-Related Transfer Functions Using the Boundary Source Representation
Authors: Bai Mingsian R. , Tsao Teng-Chieh
Published: September 2006

A technique based on the virtual source representation is presented for modeling head-related transfer functions (HRTFs). This method is motivated by the theory of simple layer potential and the principle of wave superposition. Using the virtual source representation, the HRTFs for a human head with pinnae are calculated with a minimal amount of computation. In the process, a special regularization scheme is required to calculate the equivalent strengths of virtual sources. To justify the proposed method, tests were carried out to compare the virtual source method with the boundary element method (BEM) and a direct HRTF measurement. The HRTFs obtained using the virtual source method agrees reasonably well in terms of frequency response, directional response, and impulse response with the other methods. From the numerical perspectives, the virtual source method obviates the singularity problem as commonly encountered in the BEM, and is less computationally demanding than the BEM in terms of computational time and memory storage. Subjective experiments are also conducted using the calculated and the measured HRTFs. The results reveal that the spatial characteristics of sound localization are satisfactorily reproduced as a human listener would naturally perceive by using the virtual source HRTFs.
Sensitivity of Vertebral Compressive Strength to Endplate Loading Distribution
Authors: Buckley Jenni M. , Leang Danny C. , Keaveny Tony M.
Published: September 2006

The sensitivity of vertebral body strength to the distribution of axial forces along the endplate has not been comprehensively evaluated. Using quantitative computed tomography-based finite element models of 13 vertebral bodies, an optimization analysis was performed to determine the endplate force distributions that minimized (lower bound) and maximized (upper bound) vertebral strength for a given set of externally applied axial compressive loads. Vertebral strength was also evaluated for three generic boundary conditions: uniform displacement, uniform force, and a nonuniform force distribution in which the interior of the endplate was loaded with a force that was 1.5 times greater than the periphery. Our results showed that the relative difference between the upper and lower bounds on vertebral strength was 14.2±7.0%(mean±SD). While there was a weak trend for the magnitude of the strength bounds to be inversely proportional to bone mineral density (R2=0.32, p=0.02), both upper and lower bound vertebral strength measures were well predicted by the strength response under uniform displacement loading conditions (R2=0.91 and R2=0.99, respectively). All three generic boundary conditions resulted in vertebral strength values that were statistically indistinguishable from the loading condition that resulted in an upper bound on strength. The results of this study indicate that the uncertainty in strength arising from the unknown condition of the disc is dependent on the condition of the bone (whether it is osteoporotic or normal). Although bone mineral density is not a good predictor of strength sensitivity, vertebral strength under generic boundary conditions, i.e., uniform displacement or force, was strongly correlated with the relative magnitude of the strength bounds. Thus, explicit disc modeling may not be necessary.
Simulation of Impact Test for Determining “Health” of Percutaneous Bone Anchored Implants
Authors: Jones S. , Faulkner G. , Raboud D. , Fyfe K. , Wolfaardt J.
Published: September 2006

There is an ongoing requirement for a clinically relevant, noninvasive technique to monitor the integrity of percutaneous implants used for dental restorations, bone-anchored hearing aids, and to retain extra-oral prostheses (ear, eye, nose, etc). Because of the limitations of conventional diagnostic techniques (CT, MRI), mechanical techniques that measure the dynamic response of the implant-abutment system are being developed. This paper documents a finite element analysis that simulates a transient response to mechanical impact testing using contact elements. The detailed model allows for a specific interface between the implant and bone and characterizes potential clinical situations including loss of bone margin height, loss of osseointegration, and development of a soft connective tissue layer at the bone-implant interface. The results also show that the expected difference in interface stiffness between soft connective tissue and osseointegrated bone will cause easily measurable changes in the response of the implant/abutment system. With respect to the loss of bone margin height, changes in the order of 0.2mm should be detectable, suggesting that this technique is at least as sensitive as radiography. A partial loss of osseointegration, while not being as readily evident as a bone margin loss, would still be detectable for losses as small as 0.5mm.
Water Movement in Tendon in Response to a Repeated Static Tensile Load Using One-Dimensional Magnetic Resonance Imaging
Authors: Helmer K. G. , Nair G. , Cannella M. , Grigg P.
Published: September 2006

Rabbit Achilles tendons (N=8) were subjected to tensile loading while internal water movements were followed using NMR. The distribution of the internal water in tendons was measured using a one-dimensional proton-density map that was collected along a radial line oriented transverse to the tendon’s long axis. The proton density map was created from fits to T2 relaxation data. The experimental design included two cycles of loading (7.5 N tensile load) and relaxation. The first load application was for 42.67 min: unloaded for 21.33 min, reloaded for 21.33 min, and then unloaded for 21.33 min. Water was redistributed in a time-dependent fashion upon loading: proton density decreased in the core region and increased in the rim region. In addition there was evidence that tensile loading caused water to become NMR visible. In separate, parallel experiments, we studied the mechanical behavior of tendons using identical conditions of uniaxial loading (N=7). The time constants of water movements were very different from the time constants of mechanical relaxation, indicating that water redistribution is not the sole determining factor of mechanical behavior.
Comparison of Plate-Screw Systems Used in Mandibular Fracture Reduction: Finite Element Analysis
Authors: Lovald Scott T. , Khraishi Tariq , Wagner Jon , Baack Bret , Kelly James , Wood John
Published: September 2006

A finite element model of the human dentate mandible has been developed to provide a comparison of fixation systems used currently for fracture reduction. Volume domains for cortical bone, cancellous bone, and teeth were created and meshed in ANSYS 8.0 based on IGES curves created from computerized tomography data. A unilateral molar clench was loaded on the model with a fracture gap simulated along the symphysis. Results based on Von Mises stress in cortical and cancellous bone surrounding the screws, and on fracture surface spatial fixation, show some relative differences between different screw-plate systems, yet all were judged to be appropriate in their reduction potential.
Myocardial Material Parameter Estimation—A Comparative Study for Simple Shear
Authors: Schmid H. , Nash M. P. , Young A. A. , Hunter P. J.
Published: September 2006

The study of ventricular mechanics—analyzing the distribution of strain and stress in myocardium throughout the cardiac cycle—is crucially dependent on the accuracy of the constitutive law chosen to represent the highly nonlinear and anisotropic properties of passive cardiac muscle. A number of such laws have been proposed and fitted to experimental measurements of stress-strain behavior. Here we examine five of these laws and compare them on the basis of (i) “goodness of fit:” How well they fit a set of six shear deformation tests, (ii) “determinability:” How well determined the objective function is at the optimal parameter fit, and (iii) “variability:” How well determined the material parameters are over the range of experiments. These criteria are utilized to discuss the advantages and disadvantages of the constitutive laws.