bluuebunny/crossref_metadata_2025 huggingface dataset:
Diversification of ectoparasite assemblages and climate: an example with fleas parasitic on small mammals
Authors: Krasnov Boris R. , Shenbrot Georgy I. , Khokhlova Irina S. , Poulin Robert
Published: February 2005

Aim We studied the relationships between the numbers of species and numbers of higher taxa (genera, tribes, subfamilies and families) in flea assemblages of small mammalian hosts with the aims of: (a) comparing these relationships across different regions, and (b) testing the hypothesis that flea assemblages in warmer regions diversify mainly via intrahost speciation, whereas those in colder regions diversify mainly via host switching.

Location The study used previously published data on flea assemblages on small mammalian hosts from 25 different regions of the Holarctic.

Methods The number of flea genera, tribes, subfamilies or families in an assemblage (host species) was plotted against the number of flea species in this assemblage for each region separately, and a power function was fitted to the resulting relationships. Then, the values of the exponent of the power function for a region were regressed against the mean annual temperature in this region, across all regions.

Results The relationships between the number of flea species and the numbers of flea genera, tribes, subfamilies or families on a host species in each region were found to be well described by simple power functions. The exponent of the power function of the relationship between the number of flea species and the number of flea genera per host tended to decrease with increasing local mean annual temperature. When two apparent outliers from the trend (corresponding to regions where sampling was not performed as in other regions) were omitted from the analysis, the negative relationship between temperature and the exponent of the power function between the number of flea species and number of flea genera per host became highly significant. No relationship was found between the values of the exponents of the power functions between the number of flea species and the number of flea tribes, subfamilies or families per host, and the mean local annual temperature.

Main conclusions The results suggest that the diversification of flea assemblages is associated with climatic variables. In warm regions, the greater number of congeneric species per flea assemblage, reflected by the lower exponent of the power function, may well be the outcome of intrahost speciation. This indicates that, as regional temperature increases, intrahost speciation becomes a relatively more important mode of diversification than acquisition of fleas via host switching.
Where's my dinner? Adult neurogenesis in free‐living food‐storing rodents
Authors: Barker J. M. , Wojtowicz J. M. , Boonstra R.
Published: February 2005

Postnatal hippocampal neurogenesis in wild mammals may play an essential role in spatial memory. We compared two species that differ in their reliance on memory to locate stored food. Yellow‐pine chipmunks use a single cache to store winter food; eastern gray squirrels use multiple storage sites. Gray squirrels had three times the density of proliferating cells in the dentate gyrus (determined by Ki‐67 immunostaining) than that found in chipmunks, but similar density of young neurons (determined by doublecortin immunostaining). Three explanations may account for these results. First, the larger population of young cells in squirrels may increase the flexibility of the spatial memory system by providing a larger pool of cells from which new neurons can be recruited. Second, squirrels may have a more rapid cell turnover rate. Third, many young cells in the squirrels may mature into glia rather than neurons. The densities of young neurons were higher in juveniles than in adults of both species. The relationship between adult age and cell density was more complex than that has been found in captive populations. In adult squirrels, the density of proliferating cells decreased exponentially with age, whereas in adult chipmunks the density of young neurons decreased exponentially with age.
Sensitivity to psychostimulants in mice bred for high and low stimulation to methamphetamine
Authors: Kamens H. M. , Burkhart‐Kasch S. , McKinnon C. S. , Li N. , Reed C. , Phillips T. J.
Published: February 2005

Methamphetamine (MA) and cocaine induce behavioral effects primarily through modulation of dopamine neurotransmission. However, the genetic regulation of sensitivity to these two drugs may be similar or disparate. Using selective breeding, lines of mice were produced with extreme sensitivity (high MA activation; HMACT) and insensitivity (low MA activation; LMACT) to the locomotor stimulant effects of acute MA treatment. Studies were performed to determine whether there is pleiotropic genetic influence on sensitivity to the locomotor stimulant effect of MA and to other MA‐ and cocaine‐related behaviors. The HMACT line exhibited more locomotor stimulation in response to several doses of MA and cocaine, compared to the LMACT line. Both lines exhibited locomotor sensitization to 2 mg/kg of MA and 10 mg/kg of cocaine; the magnitude of sensitization was similar in the two lines. However, the lines differed in the magnitude of sensitization to a 1 mg/kg dose of MA, a dose that did not produce a ceiling effect that may confound interpretation of studies using higher doses. The LMACT line consumed more MA and cocaine in a two‐bottle choice drinking paradigm; the lines consumed similar amounts of saccharin and quinine, although the HMACT line exhibited slightly elevated preference for a low concentration of saccharin. These results suggest that some genes that influence sensitivity to the acute locomotor stimulant effect of MA have a pleiotropic influence on the magnitude of behavioral sensitization to MA and sensitivity to the stimulant effects of cocaine. Further, extreme sensitivity to MA may protect against MA and cocaine self‐administration.
Effects of the mutation R145G in human cardiac troponin I on the kinetics of the contraction–relaxation cycle in isolated cardiac myofibrils
Authors: Kruger M. , Zittrich S. , Redwood C. , Blaudeck N. , James J. , Robbins J. , Pfitzer G. , Stehle R.
Published: February 2005

Familial hypertrophic cardiomyopathy (FHC) has been linked to mutations in sarcomeric proteins such as human cardiac troponin I (hcTnI). To elucidate the functional consequences of the mutation hcTnIR145G on crossbridge kinetics, force kinetics were analysed in murine cardiac myofibrils carrying either the mutant or the wild‐type protein. The mutation was introduced into the myofibrils in two different ways: in the first approach, the endogenous Tn was replaced by incubation of the myofibrils with an excess of reconstituted recombinant hcTn containing either hcTnIWT or hcTnIR145G. Alternatively, myofibrils were isolated either from non‐transgenic or transgenic mice expressing the corresponding mcTnIR146G mutation. In myofibrils from both models, the mutation leads to a significant upward shift of the passive force–sarcomere length relation determined at pCa 7.5. Addition of 5 mm BDM (2,3‐butandione‐2‐monoxime), an inhibitor of actomyosin ATPase partially reverses this shift, suggesting that the mutation impairs the normal function of cTnI to fully inhibit formation of force‐generating crossbridges in the absence of Ca2+. Maximum force development (Fmax) is significantly decreased by the mutation only in myofibrils exchanged with hcTnIR145Gin vitro. Ca2+ sensitivity of force development was reduced by the mutation in myofibrils from transgenic mice but not in exchanged myofibrils. In both models the rate constant of force development kACT is reduced at maximal [Ca2+] but not at low [Ca2+] where it is rather increased. Force relaxation is significantly prolonged due to a reduction of the relaxation rate constant kREL. We therefore assume that the impairment in the regulatory function of TnI by the mutation leads to modulations in crossbridge kinetics that significantly alter the dynamics of myofibrillar contraction and relaxation.
K+ secretion activated by luminal P2Y2 and P2Y4 receptors in mouse colon
Authors: Matos J. E. , Robaye B. , Boeynaems J. M. , Beauwens R. , Leipziger J.
Published: February 2005

Extracellular nucleotides are important regulators of epithelial ion transport, frequently exerting their action from the luminal side. Luminal P2Y receptors have previously been identified in rat distal colonic mucosa. Their activation by UTP and ATP stimulates K+ secretion. The aim of this study was to clarify which of the P2Y receptor subtypes are responsible for the stimulated K+ secretion. To this end P2Y2 and P2Y4 knock‐out mice were used to measure distal colonic ion transport in an Ussing chamber. In mouse (NMRI) distal colonic mucosa, luminal UTP and ATP with similar potency induced a rapid and transient increase of the transepithelial voltage (Vte) (UTP: from −0.81 ± 0.23 to 3.11 ± 0.61 mV, n= 24), an increase of equivalent short circuit current (Isc) by 166.9 ± 22.8 μA cm−2 and a decrease of transepithelial resistance (Rte) from 29.4 ± 2.4 to 23.5 ± 2.0 Ω cm2. This effect was completely inhibited by luminal Ba2+ (5 mm, n= 5) and iberiotoxin (240 nm, n= 6), indicating UTP/ATP‐stimulated K+ secretion. RT‐PCR analysis of isolated colonic crypts revealed P2Y2, P2Y4 and P2Y6 specific transcripts. The luminal UTP‐stimulated K+ secretion was still present in P2Y2 receptor knock‐out mice, but significantly reduced (ΔVte: 0.83 ± 0.26 mV) compared to wild‐type littermates (ΔVte: 2.08 ± 0.52 mV, n= 9). In P2Y4 receptor knock‐out mice the UTP‐induced K+ secretion was similarly reduced. Luminal UTP‐stimulated K+ secretion was completely absent in P2Y2/P2Y4 double receptor KO mice. Basolateral UTP showed no effect. In summary, these results indicate that both the P2Y2 and P2Y4 receptors are present in the luminal membrane of mouse distal colonic mucosa, and stimulation of these receptors leads to K+ secretion.
Mechanical activation of rectal intraganglionic laminar endings in the guinea pig distal gut
Authors: Lynn Penny , Zagorodnyuk Vladimir , Hennig Grant , Costa Marcello , Brookes Simon
Published: February 2005

The rectum receives specialized extrinsic afferent innervation by stretch‐sensitive, low threshold, slowly adapting mechanoreceptors, with transduction sites shown to correspond to rectal intraganglionic laminar endings (IGLEs). Rectal IGLEs are located in myenteric ganglia, surrounded by the longitudinal and circular smooth muscle layers; in this study we investigated the mechanical stimuli to which they respond. Mechanoreceptors had graded responses to highly focal transmural compression with von Frey hairs. They were activated when stretched circumferentially by imposed increases of both length and load. Under both conditions, firing typically occurred in bursts associated with phasic muscle contractions. However, many contractions did not evoke firing. Longitudinal stretch also evoked firing, again associated with contractile activity. Thus, mechanoreceptors did not show directional sensitivity. Two agonists that excited smooth muscle directly (0.1 μm[β‐Ala8]‐neurokinin A (4–10) and 1 μm carbachol) activated rectal mechanoreceptors, but not in the presence of Ca2+‐free solution or when preparations were kept entirely slack. We measured the dimensions, in both longitudinal and circumferential axes, of receptive fields during smooth muscle contractile activity, using video micrography. Contractile activity within the receptive field often differed significantly from the behaviour of the preparation as a whole, providing an explanation for many of the discrepancies between gross contractility and firing. Simultaneous contraction of both muscle layers within the receptive field was the strongest predictor of mechanoreceptor activation. Our results suggest that rectal mechanoreceptors do not act simply as tension receptors: rather they appear to detect mechanical deformation of myenteric ganglia – especially flattening – associated with stretch of the receptive field, or contractions of smooth muscle within the receptive field.
Differential expression of heat shock protein 27 and 70 in renal papillary collecting duct and interstitial cells – implications for urea resistance
Authors: Neuhofer Wolfgang , Fraek Maria‐Luisa , Ouyang Nengtai , Beck Franz‐X.
Published: February 2005

The adaptation of renal medullary cells to their hyperosmotic environment involves the accumulation of compatible organic osmolytes and the enhanced synthesis of heat shock proteins (HSP) 27 and 70. While the mechanisms leading to osmolyte accumulation are similar in papillary collecting duct (PCD) and papillary interstitial (PI) cells, the present data demonstrate that HSP27 and HSP70 are expressed differentially in these cells both in vivo and in vitro. HSP70 is abundant in PCD, but not expressed in PI cells in the papilla in situ, while HSP27 is expressed in both PCD and PI cells. These observations could be reproduced by non‐permeant solutes in cultured cells. Osmotic stress strongly induced HSP70 in MDCK cells (as a model for PCD cells), but not in PI cells, while HSP27 was constitutively expressed in MDCK cells and was up‐regulated in PI cells. Since prior hypertonic stress (NaCl addition) protects MDCK against subsequent exposure to high urea concentrations, this effect was also assessed in PI cells. In both cell lines, hypertonic pretreatment prior to urea exposure (400 mm) strongly attenuated caspase‐3 activation. Inhibition of HSP27 expression by antisense transfection diminished the protective effect of hypertonic preconditioning in PI cells, while attenuation of HSP70 expression in MDCK cells diminished the protective effect of hypertonic preconditioning in these cells. These observations indicate that PCD and PI cells employ cell‐specific mechanisms for protection against high urea concentrations as present in the renal papilla during antidiuresis.
5′AMP activated protein kinase expression in human skeletal muscle: effects of strength training and type 2 diabetes
Authors: Wojtaszewski Jørgen F. P. , Birk Jesper B. , Frøsig Christian , Holten Mads , Pilegaard Henriette , Dela Flemming
Published: February 2005

Strength training enhances insulin sensitivity and represents an alternative to endurance training for patients with type 2 diabetes (T2DM). The 5′AMP‐activated protein kinase (AMPK) may mediate adaptations in skeletal muscle in response to exercise training; however, little is known about adaptations within the AMPK system itself. We investigated the effect of strength training and T2DM on the isoform expression and the heterotrimeric composition of the AMPK in human skeletal muscle. Ten patients with T2DM and seven healthy subjects strength trained (T) one leg for 6 weeks, while the other leg remained untrained (UT). Muscle biopsies were obtained before and after the training period. Basal AMPK activity and protein/mRNA expression of both catalytic (α1 and α2) and regulatory (β1, β2, γ1, γ2a, γ2b and γ3) AMPK isoforms were independent of T2DM, whereas the protein content of α1 (+16%), β2 (+14%) and γ1 (+29%) was higher and the γ3 content was lower (−48%) in trained compared with untrained muscle (all P < 0.01). The majority of α protein co‐immunoprecipitated with β2 and α2/β2 accounted for the majority of these complexes. γ3 was only associated with α2 and β2 subunits, and accounted for ∼20% of all α2/β2 complexes. The remaining α2/β2 and the α1/β2 complexes were associated with γ1. The trimer composition was unaffected by T2DM, whereas training induced a shift from γ3‐ to γ1‐containing trimers. The data question muscular AMPK as a primary cause of T2DM whereas the maintained function in patients with T2DM makes muscular AMPK an obvious therapeutic target. In human skeletal muscle only three of 12 possible AMPK trimer combinations exist, and the expression of the subunit isoforms is susceptible to moderate strength training, which may influence metabolism and improve energy homeostasis in trained muscle.
Cytosolic Ca2+ concentration and rate of increase of the cytosolic Ca2+ concentration in the regulation of vascular permeability in Rana in vivo
Authors: Glass C. A. , Pocock T. M. , Curry F. E. , Bates D. O.
Published: February 2005

Vascular permeability is assumed to be regulated by the cytosolic Ca2+ concentration ([Ca2+]c) of the endothelial cells. When permeability is increased, however, the maximum [Ca2+]c appears to occur after the maximum permeability increase, suggesting that Ca2+‐dependent mechanisms other than the absolute Ca2+ concentration may regulate permeability. Here we investigate whether the rate of increase of the [Ca2+]c (d[Ca2+]c/dt) may more closely approximate the time course of the permeability increase. Hydraulic conductivity (Lp) and endothelial [Ca2+]c were measured in single perfused frog mesenteric microvessels in vivo. The relationships between the time courses of the increased Lp, [Ca2+]c and d[Ca2+]c/dt were examined. Lp peaked significantly earlier than [Ca2+]c in all drug treatments examined (Ca2+ store release, store‐mediated Ca2+ influx, and store‐independent Ca2+ influx). When Lp was increased in a store‐dependent manner the time taken for Lp to peak (3.6 ± 0.9 min during store release, 1.2 ± 0.3 min during store‐mediated Ca2+ influx) was significantly less than the time taken for [Ca2+]c to peak (9.2 ± 2.8 min during store release, 2.1 ± 0.7 min during store‐mediated influx), but very similar to that for the peak d[Ca2+]c/dt to occur (4.3 ± 2.0 min during store release, 1.1 ± 0.5 min during Ca2+ influx). Additionally, when the increase was independent of intracellular Ca2+ stores, Lp (0.38 ± 0.03 min) and d[Ca2+]c/dt (0.30 ± 0.1 min) both peaked significantly before the [Ca2+]c (1.05 ± 0.31 min). These data suggest that the regulation of vascular permeability by endothelial cell Ca2+ may be regulated by the rate of change of the [Ca2+]c rather than the global [Ca2+].
Arginine–glycine–aspartic acid (RGD)‐containing peptides inhibit the force production of mouse papillary muscle bundles via α5β1 integrin
Authors: Sarin Vandana , Gaffin Robert D. , Meininger Gerald A. , Muthuchamy Mariappan
Published: February 2005

Integrins are considered to be an important mechanosensor in cardiac myocytes. To test whether integrins can influence cardiac contractile function, the force–frequency relationships of mouse papillary muscle bundles were measured in the presence or absence of a synthetic integrin‐binding peptide, GRGDNP (gly–arg–gly–asp–asn–pro). Results demonstrate that in the presence of an arginine–glycine–aspartic acid (RGD)‐containing synthetic peptide, contractile force was depressed significantly by, 28% at 4 Hz, 37.7% at 5 Hz and 20% at 10 Hz (n= 6, P < 0.01). Treatment of myofibres with either protease‐generated fragments of denatured collagen (Type I) or denatured collagen that contain the RGD motif, also reduced force production significantly. An integrin‐activating antibody for β1 integrin inhibited the force similar to synthetic RGD peptide. Function‐blocking integrin antibodies for α5 and β1 integrins reversed the effect of the RGD‐containing peptide, and α5 integrin also reversed the effect of proteolytic fragments of denatured collagen on contractile force, whereas experiments with function‐blocking antibody for β3 integrin did not reverse the effect of RGD peptide. Force–[Ca2+]i measurements showed that the depressed rate of force generation observed in the presence of the RGD‐containing peptide was associated with reduced [Ca2+]i. Data analyses further demonstrated that force per unit of Ca2+ was reduced, suggesting that the myofilament activation process was altered. In addition, inhibition of PKC enzyme using the selective, cell‐permeable inhibitor Ro‐32‐0432, reversed the activity of RGD peptide on papillary muscle bundles. In conclusion, these data indicate that RGD peptide, acting via α5β1 integrin, depresses the force production from papillary muscle bundles, partly associated with changes in [Ca2+]i and the myofilament activation processes, that is modulated by PKCɛ.
Olivine and Pyroxene Diversity in the Crust of Mars
Authors: Mustard J. F. , Poulet F. , Gendrin A. , Bibring J.-P. , Langevin Y. , Gondet B. , Mangold N. , Bellucci G. , Altieri F.
Published: February 2005

Datafromthe Observatoire pour la Minéralogie, l'Eau, les Glaces, et l'Activité (OMEGA) on the Mars Express spacecraft identify the distinct mafic, rock-forming minerals olivine, low-calcium pyroxene (LCP), and high-calcium pyroxene (HCP) on the surface of Mars. Olivine- and HCP-rich regions are found in deposits that span the age range of geologic units. However, LCP-rich regions are found only in the ancient Noachian-aged units, which suggests that melts for these deposits were derived from a mantle depleted in aluminum and calcium. Extended dark regions in the northern plains exhibit no evidence of strong mafic absorptions or absorptions due to hydrated materials.
Summer Evolution of the North Polar Cap of Mars as Observed by OMEGA/Mars Express
Authors: Langevin Y. , Poulet F. , Bibring J.-P. , Schmitt B. , Douté S. , Gondet B.
Published: February 2005

The Observatoire pour la Minéralogie, l'Eau, les Glaces, et l'Activité (OMEGA) visible-infrared imaging spectrometer extensively observed regions of Mars with latitudes above 70°N in late 2004 (heliocentric longitude from L
s
93° to L
s
127°). The extent of water ice at the surface and the size of ice grains were monitored as a function of time. Bright, small-grained frost, which initially covered a large fraction of the polar cap, waned in favor of large-grained ice. In outlying regions, dominated by large-grained ice, the albedo increased over the period. Evaluating the dust content was model dependent. However, contamination of ice by dust was low.
Mitochondrial permeability transition in the crustaceanArtemia franciscana: absence of a calcium-regulated pore in the face of profound calcium storage
Authors: Menze Michael A. , Hutchinson Kirk , Laborde Susan M. , Hand Steven C.
Published: February 2005

When mammalian mitochondria are exposed to high calcium and phosphate, a massive swelling, uncoupling of respiration, and release of cytochrome c occur. These changes are mediated by opening of the mitochondrial permeability transition pore (MPTP). Activation of the MPTP in vivo in response to hypoxic and oxidative stress leads to necrotic and apoptotic cell death. Considering that embryos of the brine shrimp Artemia franciscana tolerate anoxia for years, we investigated the MPTP in this crustacean to reveal whether pore opening occurs. Minimum molecular constituents of the regulated MPTP in mammals are believed to be the voltage-dependent anion channel, the adenine nucleotide translocators, and cyclophilin D. Western blot analysis revealed that mitochondria from A. franciscana possess all three required components. When measured with a calcium-sensitive fluorescent probe, rat liver mitochondria are shown to release matrix calcium after addition of ≥100 μM extramitochondrial calcium (MPTP opening), whereas brine shrimp mitochondria continue to take up extramitochondrial calcium and do not release internal stores even up to 1.0 mM exogenously added calcium (no MPTP opening). Furthermore, no swelling of A. franciscana mitochondria in response to added calcium was observed, and no release of cytochrome c could be detected. HgCl2-dependent swelling and cytochrome c release were readily confirmed, which is consistent with the presence of an “unregulated pore.” Although the absence of a regulated MPTP in A. franciscana mitochondria could contribute to the extreme hypoxia tolerance in this species, we speculate that absence of the regulated MPTP may be a general feature of invertebrates.
In vivo evaluation of the effectiveness of bronchial thermoplasty with computed tomography
Authors: Brown Robert H. , Wizeman William , Danek Christopher , Mitzner Wayne
Published: February 2005

A recent study has reported that the application of thermal energy delivered through a bronchoscope (bronchial thermoplasty) impairs the ability of airway smooth muscle to shorten in response to methacholine (MCh)(Danek CJ, Lombard CM, Dungworth DL, Cox PG, Miller JD, Biggs MJ, Keast TM, Loomas BE, Wizeman WJ, Hogg JC, and Leff AR. J Appl Physiol 97: 1946–1953, 2004). If such a technique is successful, it has the potential to serve as a therapy to attenuate airway narrowing in asthmatic subjects regardless of the initiating cause that stimulates the smooth muscle. In the present study, we have applied high-resolution computed tomography to accurately quantify the changes in airway area before and after a standard MCh aerosol challenge in airways treated with bronchial thermoplasty. We studied a total of 193 airways ranging from 2 to 15 mm in six dogs. These were divided into treated and control populations. The MCh dose-response curves in untreated airways and soon-to-be-treated airways were superimposable. In contrast, the dose-response curves in treated airways were shifted upward at all points, showing a significantly decreased sensitivity to MCh at both 2 and 4 wk posttreatment. These results thus show that treated airways have significantly increased luminal area at any dose of inhaled MCh compared with untreated airways. The work in this study thus supports the underlying concept that impairing the smooth muscle may be an effective treatment for asthma.
Activator Protein-1 Mediates Shear Stress–Induced Prostaglandin D Synthase Gene Expression in Vascular Endothelial Cells
Authors: Miyagi Megumi , Miwa Yoshikazu , Takahashi-Yanaga Fumi , Morimoto Sachio , Sasaguri Toshiyuki
Published: February 2005

Objective—

We attempted to determine the molecular mechanism of fluid shear stress–induced lipocalin-type prostaglandin D synthase (
l-
PGDS) expression in vascular endothelial cells.

Methods and Results—

We examined the promoter region of the
l
-PGDS gene by loading laminar shear stress (20 dyne/cm
2
), using a parallel-plate flow chamber, on endothelial cells transfected with luciferase reporter vectors containing the 5′-flanking regions of the human
l
-PGDS gene. A deletion mutant analysis revealed that a shear stress–responsive element resided in the region between −2607 and −2523 bp. A mutation introduced into the putative binding site for activator protein-1 (AP-1) within this region eliminated the response to shear stress. In an electrophoretic mobility shift assay, shear stress stimulated nuclear protein binding to the AP-1 binding site, which was supershifted by antibodies to c-Fos and c-Jun. Shear stress elevated the c-Jun phosphorylation level in a time-dependent manner, similar to that of
l
-PGDS gene expression. SP600125, a c-Jun N-terminal kinase inhibitor, decreased the c-Jun phosphorylation, DNA binding of AP-1, and
l
-PGDS expression induced by shear stress. Additionally, an mRNA chase experiment using actinomycin D demonstrated that shear stress did not stabilize
l
-PGDS mRNA.

Conclusions—

Shear stress induces
l
-PGDS expression by transcriptional activation through the AP-1 binding site.
C-Reactive Protein Inhibits Endothelium-Dependent NO-Mediated Dilation in Coronary Arterioles by Activating p38 Kinase and NAD(P)H Oxidase
Authors: Qamirani Erion , Ren Yi , Kuo Lih , Hein Travis W.
Published: February 2005

Objective—

Elevated levels of C-reactive protein (CRP), a proinflammatory marker, are associated with reduced systemic endothelium-dependent NO-mediated dilation in patients with coronary artery disease; however, the direct effect of CRP on coronary microvascular reactivity remains unknown. Herein, we examined whether CRP can modulate endothelium-dependent NO-mediated dilation of coronary arterioles and whether proinflammatory signaling pathways such as stress-activated protein kinases (p38 and c-Jun N-terminal kinase [JNK]) and oxidative stress are involved in the CRP-mediated effect.

Methods and Results—

Porcine coronary arterioles were isolated and pressurized without flow for in vitro study. Intraluminal treatment with a clinically relevant concentration of CRP (7 μg/mL; 1 hour) significantly attenuated the NO release and vasodilation to serotonin. Further incubation with the NO precursor
l
-arginine (3 mmol/L) partially restored serotonin-induced vasodilation. In the presence of superoxide scavenger 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPOL), NAD(P)H oxidase inhibitor apocynin, or p38 kinase (an upstream activator of NAD(P)H oxidase) inhibitor SB203850, but not xanthine oxidase inhibitor allopurinol or JNK inhibitor SP600125, the detrimental effect of CRP on serotonin-induced dilation was prevented. Dihydroethidium staining showed that CRP produced SB203850- and TEMPOL-sensitive superoxide production in the arteriolar endothelium. CRP treatment of coronary arterioles significantly increased NAD(P)H oxidase activity.

Conclusions—

CRP inhibits endothelium-dependent NO-mediated dilation in coronary arterioles by producing superoxide from NAD(P)H oxidase via p38 kinase activation. By impairing endothelium-dependent NO-mediated vasoreactivity, CRP could facilitate the initiation of numerous cardiovascular diseases.
Cellular Mechanism of Calcium-Mediated Triggered Activity in the Heart
Authors: Katra Rodolphe P. , Laurita Kenneth R.
Published: February 2005

Calcium overload due to enhanced calcium entry is a mechanism for spontaneous calcium release (SCR) from the sarcoplasmic reticulum, delayed-afterdepolarizations (DAD), and triggered activity. However, the exact mechanistic relationship between elevated intracellular calcium levels and triggered activity originating from a specific location remains unclear. We hypothesize that under conditions of enhanced calcium entry, elevation of intracellular calcium will result in multiple calcium release events of which only one is more likely to initiate a triggered beat. We used optical mapping of action potentials and ratiometric calcium transients in an electromechanically-uncoupled canine wedge model of enhanced calcium entry, using
I
Ks
blockade with β-adrenergic stimulation. Under conditions of enhanced calcium entry, the rate of calcium uptake was faster compared with control conditions; however, during rapid pacing, cytoplasmic calcium elevation at the endocardium was significantly increased (15±4%) compared with control (10±3,
P
<0.04). Rapid pacing induced multiple simultaneous SCR events with largest amplitude and earliest onset near the endocardium compared with the epicardium. Furthermore, SCR events with largest amplitude and earliest onset served as a focus for DAD-mediated triggered activity. Interestingly, polymorphic VT occurred in some experiments when multiple SCR events occurred. In conclusion, multiple, simultaneous SCR events occur over a broad region of relatively slower calcium uptake and elevated diastolic calcium levels. However, SCR events closer to the endocardium have the largest amplitude and earliest onset and are, thereby, more likely to initiate DAD-mediated triggered activity. Finally, multiple SCR events may be a mechanism of polymorphic VT under calcium overload conditions.
Metabolic Inhibition Alters Subcellular Calcium Release Patterns in Rat Ventricular Myocytes
Authors: Fukumoto Gary H. , Lamp Scott T. , Motter Christi , Bridge John H.B. , Garfinkel Alan , Goldhaber Joshua I.
Published: February 2005

Metabolic inhibition (MI) contributes to contractile failure during cardiac ischemia and systolic heart failure, in part due to decreased excitation-contraction (E-C) coupling gain. To investigate the underlying mechanism, we studied subcellular Ca
2+
release patterns in whole cell patch clamped rat ventricular myocytes using two-dimensional high-speed laser scanning confocal microscopy. In cells loaded with the Ca
2+
buffer EGTA (5 mmol/L) and the fluorescent Ca
2+
-indicator fluo-3 (1 mmol/L), depolarization from −40 to 0 mV elicited a striped pattern of Ca
2+
release. This pattern represents the simultaneous activation of multiple Ca
2+
release sites along transverse-tubules. During inhibition of both oxidative and glycolytic metabolism using carbonyl cyanide-
p
-trifluoromethoxyphenylhydrazone (FCCP, 50 nmol/L) and 2-deoxyglucose (2-DG, 10 mmol/L), there was a decrease in inward Ca
2+
current (
I
Ca
), the spatially averaged Ca
2+
transient, and E-C coupling gain, but no reduction in sarcoplasmic reticulum Ca
2+
content. The striped pattern of subcellular Ca
2+
release became fractured, or disappeared altogether, corresponding to a marked decrease in the area of the cell exhibiting organized Ca
2+
release. There was no significant change in the intensity or kinetics of local Ca
2+
release. The mechanism is not fully explained by dephosphorylation of L-type Ca
2+
channels, because a similar degree of I
Ca
“rundown” in control cells did NOT result in fracturing of the Ca
2+
release pattern. We conclude that metabolic inhibition interferes with E-C coupling by (1) reducing trigger Ca
2+
, and (2) directly inhibiting sarcoplasmic reticulum Ca
2+
release site open probability.
Impairment in Postischemic Neovascularization in Mice Lacking the CXC Chemokine Receptor 3
Authors: Waeckel Ludovic , Mallat Ziad , Potteaux Stéphane , Combadière Christophe , Clergue Michel , Duriez Micheline , Bao Lu , Gerard Craig , Rollins Barrett J. , Tedgui Alain , Levy Bernard I. , Silvestre Jean-Sébastien
Published: February 2005

Inflammatory cell infiltration is a feature of postischemic neovascularization. However, mechanisms leading to leukocyte attraction to the site of neovascularization are still undefined. We hypothesized that the CXC chemokine receptor 3 (CXCR3) may contribute to leukocyte accumulation and subsequently to blood vessel growth in the ischemic area. Ischemia induced by femoral artery ligature improved the number of CXCR3-expressing cells and the level of its ligand, CXCL10. Angiographic score, blood flow recovery measurement, and capillary density analysis showed a significant decrease of ischemic/nonischemic leg ratio in CXCR3-deficient mice when compared with controls (
P
<0.05), at day 21 after ischemia. Interestingly, this impairment was as important as that observed in mice deficient for the well known CC-chemokine monocyte chemoattractant protein-1 (MCP-1). At day 7 of ischemic injury, the number of CD3-positive T cells and Mac-3–positive monocytes/macrophages was 38% and 45% lower, respectively, in the ischemic leg of CXCR3-deficient mice compared with the control group (
P
<0.05), suggesting an important role for CXCR3 in leukocyte recruitment into the ischemic area. VEGF protein content, a classical proangiogenic factor, was also markedly reduced (80% reduction) in ischemic leg of CXCR3-deficient mice (
P
<0.01). Injection of bone marrow–derived mononuclear cells (BM-MNCs) isolated from wild-type animals restored the neovascularization reaction in CXCR3-deficient mice whereas BM-MNCs from CXCR3-deficient mice was ineffective. In conclusion, CXCR3 plays a key role in neovascularization and provides novel information on the mechanisms leading to leukocyte infiltration in the vessel growth area.
Reliability of the Modified Rankin Scale Across Multiple Raters
Authors: Wilson J. T. Lindsay , Hareendran Asha , Hendry Anne , Potter Jan , Bone Ian , Muir Keith W.
Published: February 2005

Background and Purpose—

The modified Rankin Scale (mRS) is widely used to assess global outcome after stroke. The aim of the study was to examine rater variability in assessing functional outcomes using the conventional mRS, and to investigate whether use of a structured interview (mRS-SI) reduced this variability.

Methods—

Inter-rater agreement was studied among raters from 3 stroke centers. Fifteen raters were recruited who were experienced in stroke care but came from a variety of professional backgrounds. Patients at least 6 months after stroke were first assessed using conventional mRS definitions. After completion of initial mRS assessments, raters underwent training in the use of a structured interview, and patients were re-assessed. In a separate component of the study, intrarater variability was studied using 2 raters who performed repeat assessments using the mRS and the mRS-SI. The design of the latter part of the study also allowed investigation of possible improvement in rater agreement caused by repetition of the assessments. Agreement was measured using the κ statistic (unweighted and weighted using quadratic weights).

Results—

Inter-rater reliability: Pairs of raters assessed a total of 113 patients on the mRS and mRS-SI. For the mRS, overall agreement between raters was 43% (κ=0.25, κ
w
=0.71), and for the structured interview overall agreement was 81% (κ=0.74, κ
w
=0.91). Agreement between raters was significantly greater on the mRS-SI than the mRS (
P
<0.001). Intrarater reliability: Repeatability of both the mRS and mRS-SI was excellent (κ=0.81, κ
w
≥0.94).

Conclusions—

Although individual raters are consistent in their use of the mRS, inter-rater variability is nonetheless substantial. Rater variability on the mRS is thus particularly problematic for studies involving multiple raters. There was no evidence that improvement in inter-rater agreement occurred simply with repetition of the assessment. Use of a structured interview improves agreement between raters in the assessment of global outcome after stroke.
The Effect of Group Projects on Content-Related Learning
Authors: Bacon Donald R.
Published: February 2005

Business schools often assign student group projects to enhance student learning of course content and to build teamwork skills. However, the characteristics of effective collaborative learning tasks, including group goals and individual accountability, are often not found in student group projects assigned in business classes. The current research found that content learning was actually inhibited by the use of a group project. The results indicate that the students who completed a project in groups learned less of the project-related content than did students who completed a shortened version of the project individually. The characteristics of business school group projects, peer-learning projects, and group projects in the workplace are compared and contrasted. Implications for program and course design are discussed.
The Multiscale Analysis of Multiple Interacting Inclusions Problem: Finite Number of Interacting Inclusions
Authors: Buryachenko V. A. , Pagano N. J.
Published: February 2005

A hybrid method based on the combination of the volume integral equation (VIE) method and the boundary integral equation (BIE) method is proposed for the micro-macro solution of elastostatic 2D and 3D multiscale problems in bounded or unbounded solids containing interacting multiple inclusions of essentially different scale. The hybrid micro-macro formulation allows decomposition of the complete problem into two associated subproblems, one residing entirely at the micro-level and the other at the macro-level at each iteration. The efficiency of the standard iterative scheme of the BIE and VIE methods for the singular integral equations involved is enhanced by the use of a modification in the spirit of a subtraction technique as well as by the advantageous choice of the initial analytical approximation for interacting inclusions (micro-level) in an unbounded medium subjected to inhomogeneous loading. The latter is evaluated by the macro-scale BIE technique capable of handling complex finite geometries and mixed boundary conditions. The iteration method proposed converges rapidly in a wide class of problems considered with high matrix-inclusion elastic contrast, with continuously varying anisotropic and nonlinear elastic properties of inclusions, as well as with sizes of interacting inclusions differing by a factor varying in the interval from 1 to 107. The accuracy and efficiency of the method are examined through comparison with results obtained from finite-element analysis and boundary element analysis as well as from analytical solution.
Theory of Linearly Elastic Residually Stressed Plates
Authors: Paroni Roberto
Published: February 2005

The equations of a plate for a linearly elastic monoclinic material with residual stress are here derived for the first time. By using techniques of Γ-convergence we show that also in the case with residual stress the displacements are of Kirchhoff-Love type. An improvement of the result of Man and Carlson on the existence of a solution for the three-dimensional problem of linear elasticity with residual stress is also obtained.
Combined Upper Bounds on the Effective Moduli of a Perforated Elastic Plate. Numerical Assessment by Genetic Algorithm
Authors: Visdergauz S.
Published: February 2005

A thin perforated plate with square symmetry is considered in the optimization context of finding the hole shapes which maximize the effective elastic moduli of the structure. In the literature, this is usually considered as a single-criterion problem when either of the moduli is optimized independently of the others. Here, we focus on the more realistic bi-criteria problem of optimizing the bulk modulus and the first shear modulus together. By combining the genetic algorithm (GA) with the weighted sums (WS) scheme, the set of Pareto optimal moduli is found numerically in the general case of interacting holes, even near the percolation limit. The GA part of the proposed approach was previously used by the author to separately optimize the shear and Young effective moduli in perforated plates.
Gaucher disease and cancer incidence: a study from the Gaucher Registry
Authors: Rosenbloom Barry E. , Weinreb Neal J. , Zimran Ari , Kacena Katherine A. , Charrow Joel , Ward Elizabeth
Published: February 2005

Patients with Gaucher disease (GD) are alleged to be at an increased risk of malignant disorders, possibly due to potential chronic stimulation of the immune system and lymphoproliferation associated with storage of glucocerebroside in tissue macrophages. Because previous reports of increased risk of malignancy in GD may have been affected by small patient numbers and ascertainment bias, 2742 patients with GD from the International Gaucher Registry were studied. The number of cancers identified among patients in the registry was compared with that expected in the US population of similar attained age and sex. The majority of patients were young or middle-aged adults at the time of last follow-up, with only 14% older than age 60. There were 10 patients with multiple myeloma, yielding an estimated relative risk of 5.9 (95% confidence interval [95% CI]: 2.8, 10.8). The relative risk of cancer overall was 0.79 (95% CI: 0.67, 0.94), and the subgroups for cancers of the breast, prostate, colon and rectum, lung, and hematologic malignancies other than myeloma did not yield statistically significant higher risks. This study suggests that, in general, patients with Gaucher disease are not at highly increased risk of cancer, at least during early and middle age. However, there appears to be a significantly higher risk of multiple myeloma of which physicians should be aware when caring for these patients. (Blood. 2005;105:4569-4572)
Increasing stability of water-soluble PQQ glucose dehydrogenase by increasing hydrophobic interaction at dimeric interface
Authors: Tanaka Shunsuke , Igarashi Satoshi , Ferri Stefano , Sode Koji
Published: February 2005

Background

Water-soluble quinoprotein glucose dehydrogenase (PQQGDH-B) from Acinetobacter calcoaceticus has a great potential for application as a glucose sensor constituent. Because this enzyme shows no activity in its monomeric form, correct quaternary structure is essential for the formation of active enzyme. We have previously reported on the increasing of the stability of PQQGDH-B by preventing the subunit dissociation. Previous studies were based on decreasing the entropy of quaternary structure dissociation but not on increasing the interaction between the two subunits. We therefore attempted to introduce a hydrophobic interaction in the dimeric interface to increase the stability of PQQGDH-B.

Results

Amino acid residues Asn340 and Tyr418 face each other at the dimer interface of PQQGDH-B, however no interaction exists between their side chains. We simultaneously substituted Asn340 to Phe and Tyr418 to Phe or Ile, to create the two mutants Asn340Phe/Tyr418Phe and Asn340Phe/Tyr418Ile. Furthermore, residues Leu280, Val282 and Val342 form a hydrophobic region that faces, on the other subunit, residues Thr416 and Thr417, again without any specific interaction. We simultaneously substituted Thr416 and Thr417 to Val, to create the mutant Thr416Val/Thr417Val. The temperatures resulting in lose of half of the initial activity of the constructed mutants were increased by 3–4°C higher over wild type. All mutants showed 2-fold higher thermal stability at 55°C than the wild-type enzyme, without decreasing their catalytic activities. From the 3D models of all the mutant enzymes, the predicted binding energies were found to be significantly greater that in the wild-type enzyme, consistent with the increases in thermal stabilities.

Conclusions

We have achieved via site-directed mutagenesis the improvement of the thermal stability of PQQGDH-B by increasing the dimer interface interaction. Through rational design based on the quaternary structure of the enzyme, we selected residues located at the dimer interface that do not contribute to the intersubunit interaction. By substituting these residues to hydrophobic ones, the thermal stability of PQQGDH-B was increased without decreasing its catalytic activity.
Bilateral recurrent discloation of the patella associated with below knee amputation: A case report
Authors: Batra Sumit , Kumar Ratnesh , Lenka Prasanna
Published: February 2005

Background

Recurrent dislocation of the patella in patients with below knee amputation is a known entity. Abnormally high-riding patella (patella alta) and medial patellofemoral ligament insufficiency in these patients predisposes them to patellar instability. The established treatment of this problem is surgical realignment.

Case presentation

A 25 year old male patient with bilateral below knee amputation presented with bilateral recurrent dislocation of the patella while walking on knees on uneven ground. Clinical and radiographic studies showed patella alta. A simple shoe modification was used to treat this patient.

Conclusions

A simple shoe modification can be used to treat such a condition which is otherwise treated surgically.