bluuebunny/crossref_metadata_2025 huggingface dataset:
Constitutive expression of CCR2 chemokine receptor and inhibition by MCP‐1/CCL2 of GABA‐induced currents in spinal cord neurones
Authors: Gosselin Romain Daniel , Varela Carolina , Banisadr G. , Mechighel Patricia , Rostene William , Kitabgi Patrick , Melik‐Parsadaniantz Stéphane
Published: September 2005

In the CNS, immune‐like competent cells (microglia and astrocytes) were first described as potential sites of chemokine synthesis, but more recent evidence has indicated that neurones might also express chemokines and their receptors. The aim of the present work was to investigate further, both in vivo and in vitro, CC Chemokine Family Receptor 2 (CCR2) expression and functionality in rat spinal cord neurones. First, we demonstrated by RT–PCR and western blot analysis that CCR2 mRNA and protein were present in spinal extracts. Furthermore, we showed by immunolabelling that CCR2 was exclusively expressed by neurones in spinal sections of healthy rat. Finally, to test the functionality of CCR2, we used primary cultures of rat spinal neurones. In this model, similar to what was observed in vivo, CCR2 mRNA and protein were expressed by neurones. Cultured neurones stimulated with Monocyte Chemoattractant Protein‐1 (MCP‐1)/CCL2, the best characterized CCR2 agonist, showed activation of the Akt pathway. Finally, patch‐clamp recording of cultured spinal neurones was used to investigate whether MCP‐1/CCL2 could modulate their electrophysiological properties. MCP‐1 alone did not affect the electrical properties of spinal neurones, but potently and efficiently inhibited GABAA‐mediated GABAergic responses in these neurones. These data constitute the first demonstration of a modulatory role of MCP‐1 on GABAergic neurotransmission and contribute to our understanding of the roles of CCR2 and MCP‐1/CCL2 in spinal cord physiology, in particular with respect to nociceptive transmission, as well as the implication of this chemokine in neuronal adaptation or dysfunction during neuropathy.
Muscular dystrophy by merosin deficiency decreases acetylcholinesterase activity in thymus of Lama2dy mice
Authors: Nieto‐Cerón Susana , Del Campo Luis F. Sánchez , Muñoz‐Delgado Encarnación , Vidal Cecilio J. , Campoy Francisco J.
Published: August 2005

Half of congenital muscular dystrophy cases arise from laminin α2 (merosin) deficiency, and merosin‐deficient mice (Lama2dy) exhibit a dystrophic phenotype. The abnormal development of thymus in Lama2dy mice, the occurrence of acetylcholinesterase (AChE) in the gland and the impaired distribution of AChE molecules in skeletal muscle of the mouse mutant prompted us to compare the levels of AChE mRNAs and enzyme species in thymus of control and Lama2dy mice. AChE activity in normal thymus (mean ± SD 1.42 ± 0.28 µmol acetylthiocholine/h/mg protein, U/mg) was decreased by ∼50% in dystrophic thymus (0.77 ± 0.23 U/mg) (p = 0.007), whereas butyrylcholinesterase activity was little affected. RT–PCR assays revealed variable levels of R, H and T AChE mRNAs in thymus, bone marrow and spinal cord. Control thymus contained amphiphilic AChE dimers (, 64%) and monomers (, 19%), as well as hydrophilic tetramers (, 9%) and monomers (, 8%). The dimers consisted of glycosylphosphatidylinositol‐anchored H subunits. Western blot assays with anti‐AChE antibodies suggested the occurrence of inactive AChE in mouse thymus. Despite the decrease in AChE activity in Lama2dy thymus, no differences between thymuses from control and dystrophic mice were observed in the distribution of AChE forms, phosphatidylinositol‐specific phospholipase C sensitivity, binding to lectins and size of AChE subunits.
The galanin‐R2 agonist AR‐M1896 reduces glutamate toxicity in primary neural hippocampal cells
Authors: Pirondi Stefania , Fernandez Mercedes , Schmidt Ralf , Hökfelt Tomas , Giardino Luciana , Calzà Laura
Published: August 2005

Galanin is a neuropeptide involved in a variety of biological functions, including having a strong anticonvulsant activity. To assess a possible role of galanin in modulation of glutamatergic synapses and excitotoxicity, we studied effects of a galanin receptor 2(3) agonist (AR‐M1896) on several molecular events induced by glutamate administration in primary neural hippocampal cells. Exposure of cells, after 5 days in vitro, to glutamate 0.5 mm for 10 min caused morphological alterations, including disaggregation of β‐tubulin and MAP‐2 cytoskeletal protein assembly, loss of neurites and cell shrinkage. When present in culture medium together with glutamate, 1 and 10 nm of AR‐M1896 reduced these alterations. Moreover, AR‐M1896 counteracted glutamate‐induced c‐fos mRNA and c‐Fos protein up‐regulation after 30–150 min, and 24 h, respectively. Massive nuclear alterations (Hoechst 33258 staining), observed 24 h after glutamate exposure, were also antagonized by AR‐M1896 (0.1–100 nm) in a dose‐dependent manner. These findings indicate that galanin, probably mainly through its type 2 receptor, interferes with events associated with glutamate toxicity.
Inhibition of apoptosis‐inducing factor translocation is involved in protective effects of hepatocyte growth factor against excitotoxic cell death in cultured hippocampal neurons
Authors: Ishihara Naoko , Takagi Norio , Niimura Makiko , Takagi Keiko , Nakano Midori , Tanonaka Kouichi , Funakoshi Hiroshi , Matsumoto Kunio , Nakamura Toshikazu , Takeo Satoshi
Published: August 2005

Although hepatocyte growth factor (HGF) and its receptor are expressed in various regions of the brain, their effects and mechanism of action under pathological conditions remain to be determined. Over‐activation of the N‐methyl‐d‐aspartate (NMDA) receptor, an ionotropic glutamate receptor, has been implicated in a variety of neurological and neurodegenerative disorders. We investigated the effects of HGF on the NMDA‐induced cell death in cultured hippocampal neurons and sought to explore their mechanisms. NMDA‐induced cell death and increase in the number of terminal deoxynucleotidyl transferase‐mediated dUTP‐biotin nick end labeling (TUNEL)‐positive cells were prevented by HGF treatment. Although neither the total amounts nor the mitochondrial localization of Bax, Bcl‐2 and Bcl‐xL were affected, caspase 3 activity was increased after NMDA exposure. Treatment with HGF partially prevented this NMDA‐induced activation of caspase 3. Although the amount of apoptosis‐inducing factor (AIF) was not altered, translocation of AIF into the nucleus was detected after NMDA exposure. This NMDA‐induced AIF translocation was reduced by treatment with HGF. In addition, increased poly(ADP‐ribose) polymer formation after NMDA exposure was attenuated by treatment with HGF. These results suggest that the protective effects of HGF against NMDA‐induced neurotoxicity are mediated via the partial prevention of caspase 3 activity and the inhibition of AIF translocation to the nucleus.
Neuroprotective effect of N‐acetyl‐aspartyl‐glutamate in combination with mild hypothermia in the endothelin‐1 rat model of focal cerebral ischaemia
Authors: Van Hemelrijck An , Hachimi‐Idrissi Said , Sarre Sophie , Ebinger Guy , Michotte Yvette
Published: August 2005

Previously we showed that treatment with mild hypothermia (34°C for 2 h) after a focal cerebral infarct was neuroprotective by reducing apoptosis in the penumbra (cortex), but not in the core (striatum) of the infarct. In this study we examined whether administration of N‐acetyl‐aspartyl‐glutamate (NAAG) in combination with mild hypothermia could improve striatal neuroprotection in the endothelin‐1 rat model. NAAG (10 mg/kg i.p.) was injected under normothermic (37°C) or mild hypothermic conditions, either 40 min before or 20 min after the insult. NAAG reduced caspase 3 immunoreactivity in the striatum, irrespective of the time of administration and brain temperature. This neuroprotective effect could be explained, at least partially, by decreased nitric oxide synthase activity in the striatum and was blocked by the group II metabotropic glutamate receptor antagonist, LY341495. Hypothermia applied together with NAAG reduced both cortical and striatal caspase 3 immunoreactivity, as well as the overall ischaemic damage in these areas. However, no pronounced improvement was seen in total damaged brain volume. Extracellular glutamate levels did not correlate with the observed protection, whatever treatment protocol was applied. We conclude that treatment with NAAG causes the same degree of neuroprotection as treatment with hypothermia. Combination of the two treatments, although reducing apoptosis, does not considerably improve ischaemic damage.
VARIATION OF SIPHONAXANTHIN SERIES AMONG THE GENUS NEPHROSELMIS (PRASINOPHYCEAE, CHLOROPHYTA), INCLUDING A NOVEL PRIMARY METHOXY CAROTENOID1
Authors: Yoshii Yukie , Takaichi Shinichi , Maoka Takashi , Suda Shoichiro , Sekiguchi Hiroshi , Nakayama Takeshi , Inouye Isao
Published: August 2005

Carotenoid compositions were analyzed for ten strains of Nephroselmis (Prasinophyceae) containing four described and three undescribed species. Based on the distribution pattern of the siphonaxanthin series, five carotenoid types were recognized in the examined strains/species: type I (N. astigmatica Inouye et Pienaar, N. pyriformis (N. Carter) Ettl, and Nephroselmis sp1. MBIC 11158) had siphonaxanthin C12:1 and C14:1 esters as well as 6′‐OH siphonaxanthin C12:1 and C14:1 esters, type II (Nephroselmis sp2. MBIC 11149) had siphonaxanthin C8:1 ester, type III (Nephroselmis sp3. NIES 486, NIES‐PS 535, and MBIC 10871) had 19‐methoxy siphonaxanthin and siphonaxanthin C12:1 and C14:1 esters, type IV (N. spinosa Suda) had only a small amount of siphonaxanthin C12:1 ester, and type V (N. olivacea Stein) had lutein as a major carotenoid but completely lacked the siphonaxanthin series. 19‐Methoxy siphonaxanthin was a novel and very unique carotenoid, that is, it contains a methoxy group and was found for the first time in photosynthetic eukaryotes. Additionally, carotenoids containing a primary methoxy group had previously never been found in any group of organisms. Siphonaxanthin C8:1 ester, which was only known as a trace carotenoid in Chlamydomonas parkeae Ettl, was first discovered as a major carotenoid in Nephroselmis sp2. (MBIC 11149). Based on these results and comparison of the phylogenetic relationships of the Nephroselmis species used, we discuss the taxonomic significance of the carotenoid types and evolutionary process of the photosynthetic antenna systems in green plants.
CLATHROMORPHUM NEREOSTRATUM(CORALLINALES, RHODOPHYTA): THE OLDEST ALGA?1
Authors: Frantz Brian R. , Foster Michael S. , Riosmena‐Rodríguez Rafael
Published: August 2005

The longevity of organisms is intrinsically interesting and can provide useful information on their population structure and dynamics and the dynamics of associated communities. With the exception of perennial Laminariales that have rings in the stipe, the life spans of most perennial macroalgae are unknown or based on anecdotal observations. Using morphological analyses combined with the location and time of the rise in14C from atmospheric nuclear testing within the thallus, we determined that the growth rate of a specimen ofClathromorphum nereostratumLebednik from Adak Island was 0.30 mm·yr−1, the 30bands within the thallus were annual, and the specimen sampled was 61–75 years old. Living crusts of this species from the same geographic region are reported to be up to 20 cm thick. Assuming our growth rate is typical,C. nereostratumcan be approximately 700 years old, the oldest known living alga. This longevity and consistent banding within the thallus suggest that smaller scale sampling and additional chemical analyses of this alga could provide a detailed long‐term record of environmental variation at high latitudes in the North Pacific.
ACCLIMATION OFEMILIANIA HUXLEYI(PRYMNESIOPHYCEAE) TO PHOTON FLUX DENSITY1
Authors: Harris Gayle N. , Scanlan David J. , Geider Richard J.
Published: August 2005

Growth rate, pigment composition, and noninvasive chlafluorescence parameters were assessed for a noncalcifying strain of the prymnesiophyteEmiliania huxleyiLohman grown at 50, 100, 200, and 800 μmol photons·m−2·s−1.Emiliania huxleyigrown at high photon flux density (PFD) was characterized by increased specific growth rates, 0.82 d−1for high PFD grown cells compared with 0.38 d−1for low PFD grown cells, and higherin vivochlaspecific attenuation coefficients that were most likely due to a decreased pigment package, consistent with the observed decrease in cellular photosynthetic pigment content. High PFD growth conditions also induced a 2.5‐fold increase in the pool of the xanthophyll cycle pigments diadinoxanthin and diatoxanthin responsible for dissipation of excess energy. Dark‐adapted maximal photochemical efficiency (Fv/Fm) remained constant at around 0.58 for cells grown over the range of PFDs, and therefore the observed decline, from 0.57 to 0.33, in the PSII maximum efficiency in the light‐adapted state, (Fv′/Fm′), with increasing growth PFD was due to increased dissipation of excess energy, most likely via the xanthophyll cycle and not due to photoinhibition. The PSII operating efficiency (Fq′/Fm′) decreased from 0.48 to 0.21 with increasing growth PFD due to both saturation of photochemistry and an increase in nonphotochemical quenching. The changes in the physiological parameters with growth PFD enableE. huxleyito maximize rates of photosynthesis under subsaturating conditions and protect the photosynthetic apparatus from excess energy while supporting higher saturating rates of photosynthesis under saturating PFDs.
THE EFFECTS OF PHOSPHITE ON PHOSPHATE STARVATION RESPONSES OF ULVA LACTUCA (ULVALES, CHLOROPHYTA)1
Authors: Lee Tse‐Min , Tsai Pei‐Fen , Shyu Yuang‐Tay , Sheu Fuu
Published: August 2005

Effects of phosphite (Phi) on phosphate (Pi) starvation responses were determined in Ulva lactuca L. by incubation in Pi‐limited (1 μM NaH2PO4) or Pi‐sufficient (100 μM NaH2PO4) seawater containing 0–3 mM Phi. Exposure to 1 μM NaH2PO4 decreased the growth rate and the content of free Pi and esterified‐P but increased the activities of extracellular alkaline phosphatase (EC 3.1.2.1) and intracellular acid phosphatase (ACP; EC 3.1.2.2); two ACP isozymes observed by activity staining on isoelectric focussing (IEF) gel were induced. The Km value of Pi uptake rate was decreased by incubation with 1 μM NaH2PO4 and the decrease in Km value was inhibited by 2 mM Phi, reflecting the operation of a high‐affinity Pi uptake system at low Pi concentrations. In the presence of Phi, the growth rate of Pi‐sufficient and Pi‐starved thalli decreased as Phi concentrations were increased from 0 to 2 mM. As Phi concentrations were increased from 0 to 2 mM, the free Pi contents in both Pi‐sufficient and Pi‐starved thalli decreased, but the esterified‐P contents in Pi‐starved thalli increased, whereas those in Pi‐sufficient thalli increased at 1 mM Phi and decreased at 2 mM Phi. Cell wall localized AP activity in both Pi‐sufficient and Pi‐starved thalli decreased as Phi concentrations were increased from 0 to 2 mM. Intracellular ACP activity in Pi‐starved thalli decreased as Phi concentrations were increased from 0 to 2 mM but was not affected in Pi‐sufficient thalli. The induction of ACP isozyme activity and high‐affinity Pi uptake system in Pi‐starved thalli was inhibited by Phi. The present investigation shows that Phi interrupts the sensing mechanisms of U. lactuca to Pi‐limiting conditions.
AN SEM‐BASED ANALYSIS OF THE MORPHOLOGY, ANATOMY, AND REPRODUCTION OF LITHOTHAMNION TOPHIFORME (ESPER) UNGER (CORALLINALES, RHODOPHYTA), WITH A COMPARATIVE STUDY OF ASSOCIATED NORTH ATLANTIC ARCTIC/SUBARCTIC MELOBESIOIDEAE1
Authors: Adey Walter H. , Chamberlain Yvonne M. , Irvine Linda M.
Published: August 2005

Lithothamnion tophiforme (Esper) Unger is a dominant, arctic, saxicolous species that extends southward, albeit with reduced cover, into the deeper colder waters of the North Atlantic subarctic, where it also occurs in significant rhodolith deposits with L. glaciale. The external appearance of L. tophiforme is distinctive, but typification, anatomy, reproduction, ecology, and biogeography have not been previously analyzed. These topics are now addressed, with extensive use of SEM, in comparison with other North Atlantic arctic and subarctic melobesioid genera and species. The species considered in this article comprise 95% of the coralline biomass of the colder North Atlantic and adjacent arctic (i.e. less than 12° C summer and less than 0° C winter). In the outer thallus region of coralline algae, crust extension proceeds, calcification develops, surface sloughing and grazing occur, and reproductive structures are initiated. Analysis of the ultrastructure of the outer thallus region (epithallium, meristem, and perithallium) of L. tophiforme shows distinctive generic similarities and specific differences from the other Lithothamnion species discussed here. Considerable generic differences from the Clathromorpum and Leptophytum species also encountered in the region considered are highlighted as well. We discuss the functional and taxonomic implications of these distinguishing features and recommend that they be more widely considered in future research on coralline algae to understand more fully the ecology and evolution of the Corallinales.
Associations Between G/A1229, A/G3944, T/C30875, C/T48200 and C/T65013 Genotypes and Haplotypes in the Vitamin D Receptor Gene, Ultraviolet Radiation and Susceptibility to Prostate Cancer
Authors: Moon Sam , Holley Sarah , Bodiwala Dhaval , Luscombe Christopher J. , French Michael E. , Liu Samson , Saxby Mark F. , Jones Peter W. , Fryer Anthony A. , Strange Richard C.
Published: August 2005

Ultraviolet radiation (UVR) may protect against prostate cancer via a mechanism involving vitamin D. Thus, the vitamin D receptor (VDR) gene is a susceptibility candidate, though published data are discrepant. We studied the association of prostate cancer risk with five VDR single nucleotide polymorphisms (SNPs): G/A1229 (SNP 1), A/G3944 (SNP 2), T/C30875 (SNP 3), C/T48200 (SNP 4) and C/T65013 (SNP 5), in 430 cancer and 310 benign prostatic hypertrophy (BPH) patients. The SNP 2 GG genotype frequency was lower in cancer than BPH patients (odds ratio = 0.63, 95% CI = 0.41–0.98, p = 0.039). SNPs 1 and 2, and SNPs 4 and 5, were in linkage disequilibrium. Two copies of haplotypes comprising SNPs 1‐2, G‐G (odds ratio = 0.63, p = 0.039), SNPs 2‐3 G‐C (odds ratio = 0.45, p = 0.008) and SNPs 1‐2‐3 G‐G‐C (odds ratio = 0.44, p = 0.006), but not SNPs 1‐3, G‐C (odds ratio = 0.81, p = 0.34), were associated with reduced risk (reference, no copies of the haplotypes). These associations were observed after stratification of subjects by extent of UVR exposure. These data show that SNP 2 GG genotype mediates prostate cancer risk, complementing studies reporting this allele is protective in malignant melanoma pathogenesis. They further suggest that published associations of risk with SNP 1 may result from linkage disequilibrium with SNP 2.
Mitochondrial DNA Diversity in the Polish Roma
Authors: Malyarchuk B. A. , Grzybowski T. , Derenko M. V. , Czarny J. , Miścicka‐Śliwka D.
Published: August 2005

Mitochondrial DNA variability in the Polish Roma population has been studied by means of hypervariable segment I and II (HVS I and II) sequencing and restriction fragment‐length polymorphism analysis of the mtDNA coding region. The mtDNA haplotypes detected in the Polish Roma fall into the common Eurasian mitochondrial haplogroups (H, U3, K, J1, X, I, W, and M*). The results of complete mtDNA sequencing clearly indicate that the Romani M*‐lineage belongs to the Indian‐specific haplogroup M5, which is characterized by three transitions in the coding region, at sites 12477, 3921 and 709. Molecular variance analysis inferred from mtDNA data reveals that genetic distances between the Roma groups are considerably larger than those between the surrounding European populations. Also, there are significant differences between the Bulgarian Roma (Balkan and Vlax groups) and West European Roma (Polish, Lithuanian and Spanish groups). Comparative analysis of mtDNA haplotypes in the Roma populations shows that different haplotypes appear to demonstrate impressive founder effects: M5 and H (16261–16304) in all Romani groups; U3, I and J1 in some Romani groups. Interestingly, haplogroup K (with HVS I motif 16224‐16234‐16311) found in the Polish Roma sample seems to be specific for Ashkenazi Jewish populations.
THE ANTARCTIC PSYCHROPHILE, CHLAMYDOMONAS RAUDENSIS ETTL (UWO241) (CHLOROPHYCEAE, CHLOROPHYTA), EXHIBITS A LIMITED CAPACITY TO PHOTOACCLIMATE TO RED LIGHT1
Authors: Morgan‐Kiss Rachael M. , Ivanov Alexander G. , Pocock Tessa , Król Marianna , Gudynaite‐Savitch Loreta , Hüner Norman P. A.
Published: August 2005

The psychrophilic Antarctic alga, Chlamydomonas raudensis Ettl (UWO241), grows under an extreme environment of low temperature and low irradiance of a limited spectral quality (blue‐green). We investigated the ability of C. raudensis to acclimate to long‐term imbalances in excitation caused by light quality through adjustments in photosystem stoichiometry. Log‐phase cultures of C. raudensis and C. reinhardtii grown under white light were shifted to either blue or red light for 12 h. Previously, we reported that C. raudensis lacks the ability to redistribute light energy via the short‐term mechanism of state transitions. However, similar to the model of mesophilic alga, C. reinhardtii, the psychrophile retained the capacity for long‐term adjustment in energy distribution between PSI and PSII by modulating the levels of PSI reaction center polypeptides, PsaA/PsaB, with minimal changes in the content of the PSII polypeptide, D1, in response to changes in light quality. The functional consequences of the modulation in PSI/PSII stoichiometry in the psychrophile were distinct from those observed in C. reinhardtii. Exposure of C. raudensis to red light caused 1) an inhibition of growth and photosynthetic rates, 2) an increased reduction state of the intersystem plastoquinone pool with concomitant increases in nonphotochemical quenching, 3) an uncoupling of the major light‐harvesting complex from the PSII core, and 4) differential thylakoid protein phosphorylation profiles compared with C. reinhardtii. We conclude that the characteristic low levels of PSI relative to PSII set the limit in the capacity of C. raudensis to photoacclimate to an environment enriched in red light.
Role of Microscopic Tissue Structure in Shock‐Induced Activation Assessed by Optical Mapping in Myocyte Cultures
Authors: CHEEK ERIC R. , SHARIFOV OLEG F. , FAST VLADIMIR G.
Published: August 2005

Introduction: Termination of ventricular fibrillation by electric shocks is believed to be due to the direct activation of large tissue mass that may be caused by microscopic virtual electrodes formed at discontinuities in tissue structure. Here, microscopic shock‐induced activation was measured optically in myocyte cultures; spatially averaged microscopic Vm measurements were compared with macroscopic measurements from left ventricular (LV) tissue.

Methods and Results: Experiments were performed in linear cell strands of different width (∼0.1 and 0.8 mm) and isolated porcine LV preparations. Uniform field shocks were applied across strands or LV preparations during diastole and action potential (AP) plateau. Depending on shock strength, three different types of activation were observed in cell strands. Weakest shocks produced “delayed make” activation that started on the cathodal strand side after long latency and rapidly spread to the anodal side. Stronger shocks caused “make” activation with short latency and rapid spread across strands. Strongest shocks caused nonuniform “make‐break” activation where the cathodal side was activated with a short latency but activation of the anodal side was delayed until after the shock end due to a large negative shock‐induced polarization. Spatial averaging of Vm responses across 0.1‐mm (but not 0.8‐mm) strands resulted in AP upstrokes and plateau polarizations that closely resembled the Vm responses measured in LV myocardium. The shock strength for the transition between fast and delayed activation in 0.1‐mm cell strands and LV myocardium was similar as well.

Conclusion: These data provide evidence that microscopic tissue structures with dimensions of approximately hundred microns are responsible for shock‐induced activation of ventricular tissue.
Intramural Measurement of Transmembrane Potential in the Isolated Pig Heart: Validation of a Novel Technique
Authors: CALDWELL BRYAN J. , LEGRICE IAN J. , HOOKS DARREN A. , TAI DEAN C.‐S. , PULLAN ANDREW J. , SMAILL BRUCE H.
Published: August 2005

Introduction: Transmembrane potentials can be recorded at multiple intramural sites in the intact heart using fiber optic probes or optrodes. The technique has considerable potential utility for studies of arrhythmia and defibrillation, but has not been validated in large mammalian hearts.

Methods and Results: An optrode was used to acquire intramural transmembrane potentials in six isolated Langendorff‐perfused pig hearts. Mechanical activity was suppressed with 2,3‐butanedione monoxime (BDM). Excitation light (488 nm) was delivered to and fluorescence collected from six sites, each spaced 1.4 mm apart across the left ventricle (LV) free wall that was stained with di‐4 ANEPPS. Intramural membrane potentials were compared with extracellular potentials recorded at adjacent locations in sinus rhythm, and during atrial and subepicardial ventricular pacing (1–3 Hz). In three hearts, epicardial intracellular potentials were also measured close to the optrode. Optical action potentials were reproducible, with no significant transmural variation in morphology. There was close correspondence between subepicardial optical and intracellular potentials (R2= 0.948, n = 23). The onset of activation at and its progression across adjacent optical and extracellular recording sites were consistent, as was the variation of action potential duration (APD) with cycle length. However, there was greater variability in absolute APD estimated from optical and extracellular records (R2= 0.773, n = 258). Comparison of extracellular potentials at the same intramural sites in vivo confirms that heart isolation and BDM slow electrical propagation and depress restitution relationships, but otherwise preserve intramural patterns of electrical activation.

Conclusions: We have demonstrated that our optrode provides reliable intramural transmembrane potential recordings in the isolated pig heart preparation.
The Mechanism of Pause‐Induced Torsade de Pointes in Long QT Syndrome
Authors: LIU JINQIU , LAURITA KENNETH R.
Published: August 2005

Introduction: Torsade de pointes (TdP), is often preceded by a short‐long cycle length sequence. However, the causal relationship between the pause associated with a short‐long cycle length sequence and TdP is not completely understood. This study tests the hypothesis that a pause enhances both dispersion of repolarization and EAD formation; however, EADs that form where APD is longest will be less likely to initiate TdP.

Methods and Results: We used optical mapping to measure transmural action potentials from the canine left ventricular wedge preparation. D‐sotalol and ATX‐II were used to mimic LQT2 and LQT3, respectively. The pause significantly enhanced mean APD (from 356 ± 20 to 381 ± 25 msec in LQT2, P < 0.05; from 609 ± 92 to 675 ± 98 msec in LQT3, P < 0.05) and transmural dispersion (from 35 ± 9 to 46 ± 11 msec in LQT2, P < 0.05; from 121 ± 85 to 171 ± 98 msec in LQT3, P < 0.05) compared to steady state pacing. Under LQT3 condition EADs, EAD‐induced triggered activity, and TdP were more likely to occur following a pause. Interestingly, the triggered beat following a pause always broke through at the region of maximum local repolarization gradient.

Conclusion: These data suggest that a pause accentuates transmural repolarization gradients and facilitates the formation of EADs and EAD‐induced triggered activity. In contrast to our hypothesis, the findings of this study support the concept that M‐cells (where APD is longest) can play an important role in both the origination of EAD‐induced triggered activity and unidirectional block associated with TdP.
Sometimes Higher Heart Rate Variability Is Not Better Heart Rate Variability: Results of Graphical and Nonlinear Analyses
Authors: STEIN PHYLLIS K. , DOMITROVICH PETER P. , HUI NELSON , RAUTAHARJU PENTTI , GOTTDIENER JOHN
Published: August 2005

Objective: To determine the prevalence and effect on traditional heart rate variability (HRV) indices of abnormal HRV patterns in the elderly.

Methods: Hourly Poincaré plots and plots of spectral HRV from normal‐to‐normal interbeat intervals and hourly nonlinear HRV values were examined in a subset of 290 consecutive participants in the Cardiovascular Health Study. Only subjects in normal sinus rhythm with ≥18 hours of usable data were included. Eligible subjects were 71 ± 5 years. During 7 years of follow‐up, 21.7% had died. Hours were scored as normal (0), borderline (0.5), or abnormal (1) from a combination of plot appearance and HRV. Summed scores were normalized to 100% to create an abnormality score (ABN). Short‐term HRV versus each 5th percentile of ABN was plotted and a cutpoint for markedly increased HRV identified. The t‐tests compared HRV for subjects above and below this cutpoint. Cox regression evaluated the association of ABN and mortality.

Results: Of 5,815 eligible hourly plots, 64.4% were normal, 14.5% borderline, and 21.1% abnormal. HR, SDNN, SDNNIDX, ln VLF and LF power, and power law slope did not differ by the cutpoint for increased short‐term HRV, while SDANN and ln ULF power were significantly lower for those above the cutpoint. However, many HRV indices including LF/HF ratio and normalized LF and HF power were significantly different between groups (P < 0.001). Increased ABN was significantly associated with mortality (P = 0.019). Despite similar values for many HRV indices, being in the group above the cutpoint was significantly associated with mortality (P = 0.04).

Conclusions: Abnormal HR patterns that elevate many HRV indices are prevalent among the elderly and associated with higher risk of mortality. Consideration of abnormal HRV may improve HRV‐based risk stratification.
Clinical Prediction of Cavotricuspid Isthmus Dependence in Patients Referred for Catheter Ablation of “Typical” Atrial Flutter
Authors: LICKFETT LARS , CALKINS HUGH , NASIR KHURRAM , DICKFELD TIMM , ELDADAH ZAYD , JAYAM VINOD , LENG CHARLES , TOMASELLI GORDON , DONAHUE KEVIN , HALPERIN HENRY , LÜDERITZ BERNDT , BERGER RONALD
Published: August 2005

Introduction: Typical atrial flutter (AFL) can be cured by catheter ablation of the cavotricuspid isthmus (CTI). The surface electrocardiogram (ECG) is not always diagnostic of isthmus dependence of AFL. The aim of this study was to evaluate clinical parameters for the prediction of isthmus‐dependent AFL.

Methods and Results: Sixty consecutive adult patients without suspected atriotomy‐related AFL, congenital heart disease, or previous AFL ablation, referred for catheter ablation of presumed typical AFL were studied. All patients had distinct flutter waves in the inferior leads, suggestive of CTI‐dependent AFL, either on presentation to the electrophysiology (EP) lab or documented on prior ECG. Electrophysiology study was performed in the standard fashion. Patients who presented to the EP laboratory not in AFL underwent arrhythmia induction with a burst pacing protocol.

A clinical history of persistent AFL (P = 0.0001) and existence of AFL on presentation to the EP laboratory (P = 0.0001) were strong predictors of CTI dependence. History of atrial fibrillation (P = 0.19), structural heart disease (P = 0.6), hypertension (P = 0.4), and previous cardiac surgery (P = 0.5), as well as the nature of AFL‐related symptoms (P = 0.5), were not predictors of CTI‐dependent AFL documented during EP study.

Conclusion: In patients with ECG suggestive of typical AFL, the presence of persistent rather than paroxysmal AFL and presentation to the EP laboratory in AFL are strong predictors of CTI‐dependent AFL. A paroxysmal pattern of AFL predicts noninducibility of CTI‐dependent AFL during EP study. CTI ablation may therefore be less effective in these patients.
Efficacy and Safety of Cryoenergy in the Ablation of Atrioventricular Reentrant Tachycardia Substrates in Children and Adolescents
Authors: KRIEBEL THOMAS , BROISTEDT CLAUDIA , KROLL MAJA , SIGLER MATTHIAS , PAUL THOMAS
Published: August 2005

Introduction: Cryoenergy has evolved as a safe and effective alternative for ablation of arrhythmia substrates in adult patients. Due to two specific features, cryomapping and cryoadhesion, this technique appears very attractive for pediatric patients minimizing complications and fluoroscopy time. The aim of the study was to investigate efficacy and safety of cryoenergy in the ablation of supraventricular tachycardia (SVT) substrates in pediatric patients.

Patients and Methods: Thirty‐two patients (mean age: 10.1 ± 3.5 years) with SVT (accessory pathways: n = 19; atrioventricular nodal reentrant tachycardia (AVNRT): n = 13) underwent electrophysiological study under the guidance of the LocaLisa® system. Cryomapping at −30°C was performed to predict cryoablation outcome and to ascertain AV conduction. Cryoenergy was delivered subsequently at the same spot (cryoablation at −70°C) as verified by the LocaLisa® system.

Results: Successful cryoablation was achieved in 24 of 32 patients (75%). A median of two (1–10) cryoablations were delivered. In the remaining 8 patients, radiofrequency (RF) current application was effective in 5 resulting in an overall success rate of 90.6%. In 4 patients with an accessory pathway cryomapping was not predictive for successful cryoablation (negative predictive value 66.6%). In 3 additional patients with AVNRT transient high‐grade AV block occurred during cryoablation despite previous “safe” cryomapping at the same location. No other major complications were noted.

Conclusion: Cryoablation of SVT substrates in pediatric patients was associated with a lower success rate compared to RF catheter ablation. Cryomapping decreased the number of permanent lesions but did not predict cryoablation outcome in all tachycardia substrates.
Bias Adjustment in Bayesian Estimation of Bird Nest Age‐Specific Survival Rates
Authors: Cao Jing , He Chong Z.
Published: August 2005

Summary The populations of many North American landbirds are showing signs of declining. Gathering information on breeding productivity allows early detection of unhealthy populations and helps develop good habitat‐management practices. In this paper, we study the performance of the Bayesian model (He, 2003, Biometrics59, 962–973) for age‐specific nest survival rates with irregular visits. We find that the estimates are satisfactory except for the age‐one survival rate. Usually the more days skipped between two visits, the more serious the underestimation of the age‐one survival rate. We investigated the problem and developed three approaches to adjust for the underestimation bias. The simulation results show that the three approaches can significantly improve the estimation of the age‐one survival rate.
Comments about Joint Modeling of Cluster Size and Binary and Continuous Subunit‐Specific Outcomes
Authors: Gueorguieva Ralitza V.
Published: August 2005

Summary In longitudinal studies and in clustered situations often binary and continuous response variables are observed and need to be modeled together. In a recent publication Dunson, Chen, and Harry (2003, Biometrics59, 521–530) (DCH) propose a Bayesian approach for joint modeling of cluster size and binary and continuous subunit‐specific outcomes and illustrate this approach with a developmental toxicity data example. In this note we demonstrate how standard software (PROC NLMIXED in SAS) can be used to obtain maximum likelihood estimates in an alternative parameterization of the model with a single cluster‐level factor considered by DCH for that example. We also suggest that a more general model with additional cluster‐level random effects provides a better fit to the data set. An apparent discrepancy between the estimates obtained by DCH and the estimates obtained earlier by Catalano and Ryan (1992, Journal of the American Statistical Association87, 651–658) is also resolved. The issue of bias in inferences concerning the dose effect when cluster size is ignored is discussed. The maximum‐likelihood approach considered herein is applicable to general situations with multiple clustered or longitudinally measured outcomes of different type and does not require prior specification and extensive programming.
Bayesian Analysis for Generalized Linear Models with Nonignorably Missing Covariates
Authors: Huang Lan , Chen Ming‐Hui , Ibrahim Joseph G.
Published: August 2005

SummaryWe propose Bayesian methods for estimating parameters in generalized linear models (GLMs) with nonignorably missing covariate data. We show that when improper uniform priors are used for the regression coefficients,φ, of the multinomial selection model for the missing data mechanism, the resulting joint posterior will always be improper if (i) all missing covariates are discrete and an intercept is included in the selection model for the missing data mechanism, or (ii) at least one of the covariates is continuous and unbounded. This impropriety will result regardless of whether proper or improper priors are specified for the regression parameters,β, of the GLM or the parameters,α, of the covariate distribution. To overcome this problem, we propose a novel class of proper priors for the regression coefficients,φ, in the selection model for the missing data mechanism. These priors are robust and computationally attractive in the sense that inferences aboutβare not sensitive to the choice of the hyperparameters of the prior forφand they facilitate a Gibbs sampling scheme that leads to accelerated convergence. In addition, we extend the model assessment criterion ofChen, Dey, and Ibrahim(2004a,Biometrika91,45–63), called theweighted L measure, to GLMs and missing data problems as well as extend the deviance information criterion (DIC) ofSpiegelhalter et al.(2002,Journal of the Royal Statistical Society B64,583–639) for assessing whether the missing data mechanism is ignorable or nonignorable. A novel Markov chain Monte Carlo sampling algorithm is also developed for carrying out posterior computation. Several simulations are given to investigate the performance of the proposed Bayesian criteria as well as the sensitivity of the prior specification. Real datasets from a melanoma cancer clinical trial and a liver cancer study are presented to further illustrate the proposed methods.
Stratified Analysis in Randomized Trials with Noncompliance
Authors: Matsui Shigeyuki
Published: August 2005

Summary This article develops methods for stratified analyses of additive or multiplicative causal effect on binary outcomes in randomized trials with noncompliance. The methods are based on a weighted estimating function for an unbiased estimating function under randomization in each stratum. When known weights are used, the derived estimator is a natural extension of the instrumental variable estimator for stratified analyses, and test‐based confidence limits are solutions of a quadratic equation in the causal parameter. Optimal weights that maximize asymptotic efficiency incorporate variability in compliance aspects across strata. An assessment based on asymptotic relative efficiency shows that a substantial enhancement in efficiency can be gained by using optimal weights instead of conventional ones, which do not incorporate the variability in compliance aspects across strata. Application to a field trial for coronary heart disease is provided.
Generalized Linear Latent Variable Models for Repeated Measures of Spatially Correlated Multivariate Data
Authors: Zhu J. , Eickhoff J. C. , Yan P.
Published: August 2005

SummaryObservations of multiple‐response variables across space and over time occur often in environmental and ecological studies. Compared to purely spatial models for a single response variable in the exponential family of distributions, fewer statistical tools are available for multiple‐response variables that are not necessarily Gaussian. An exception is a common‐factor model developed for multivariate spatial data byWang and Wall(2003,Biostatistics4,569–582). The purpose of this article is to extend this multivariate space‐only model and develop a flexible class of generalized linear latent variable models for multivariate spatial–temporal data. For statistical inference, maximum likelihood estimates and their standard deviations are obtained using a Monte Carlo EM algorithm. We also use a novel way to automatically adjust the Monte Carlo sample size, which facilitates the convergence of the Monte Carlo EM algorithm. The methodology is illustrated by an ecological study of red pine trees in response to bark beetle challenges in a forest stand of Wisconsin.
Combining Multiple Comparisons and Modeling Techniques in Dose‐Response Studies
Authors: Bretz F. , Pinheiro J. C. , Branson M.
Published: August 2005

Summary The analysis of data from dose‐response studies has long been divided according to two major strategies: multiple comparison procedures and model‐based approaches. Model‐based approaches assume a functional relationship between the response and the dose, taken as a quantitative factor, according to a prespecified parametric model. The fitted model is then used to estimate an adequate dose to achieve a desired response but the validity of its conclusions will highly depend on the correct choice of the a priori unknown dose‐response model. Multiple comparison procedures regard the dose as a qualitative factor and make very few, if any, assumptions about the underlying dose‐response model. The primary goal is often to identify the minimum effective dose that is statistically significant and produces a relevant biological effect. One approach is to evaluate the significance of contrasts between different dose levels, while preserving the family‐wise error rate. Such procedures are relatively robust but inference is confined to the selection of the target dose among the dose levels under investigation. We describe a unified strategy to the analysis of data from dose‐response studies which combines multiple comparison and modeling techniques. We assume the existence of several candidate parametric models and use multiple comparison techniques to choose the one most likely to represent the true underlying dose‐response curve, while preserving the family‐wise error rate. The selected model is then used to provide inference on adequate doses.
Bayesian Inference for Stochastic Kinetic Models Using a Diffusion Approximation
Authors: Golightly A. , Wilkinson D. J.
Published: August 2005

Summary This article is concerned with the Bayesian estimation of stochastic rate constants in the context of dynamic models of intracellular processes. The underlying discrete stochastic kinetic model is replaced by a diffusion approximation (or stochastic differential equation approach) where a white noise term models stochastic behavior and the model is identified using equispaced time course data. The estimation framework involves the introduction of m− 1 latent data points between every pair of observations. MCMC methods are then used to sample the posterior distribution of the latent process and the model parameters. The methodology is applied to the estimation of parameters in a prokaryotic autoregulatory gene network.
On Corrected Score Approach for Proportional Hazards Model with Covariate Measurement Error
Authors: Song Xiao , Huang Yijian
Published: August 2005

Summary In the presence of covariate measurement error with the proportional hazards model, several functional modeling methods have been proposed. These include the conditional score estimator (Tsiatis and Davidian, 2001, Biometrika88, 447–458), the parametric correction estimator (Nakamura, 1992, Biometrics48, 829–838), and the nonparametric correction estimator (Huang and Wang, 2000, Journal of the American Statistical Association95, 1209–1219) in the order of weaker assumptions on the error. Although they are all consistent, each suffers from potential difficulties with small samples and substantial measurement error. In this article, upon noting that the conditional score and parametric correction estimators are asymptotically equivalent in the case of normal error, we investigate their relative finite sample performance and discover that the former is superior. This finding motivates a general refinement approach to parametric and nonparametric correction methods. The refined correction estimators are asymptotically equivalent to their standard counterparts, but have improved numerical properties and perform better when the standard estimates do not exist or are outliers. Simulation results and application to an HIV clinical trial are presented.
Smooth Tests for the Zero‐Inflated Poisson Distribution
Authors: Thas Olivier , Rayner J. C. W.
Published: August 2005

Summary In this article we construct three smooth goodness‐of‐fit tests for testing for the zero‐inflated Poisson (ZIP) distribution against general smooth alternatives in the sense of Neyman. We apply our tests to a data set previously claimed to be ZIP distributed, and show that the ZIP is not a good model to describe the data. At rejection of the null hypothesis of ZIP, the individual components of the test statistic, which are directly related to interpretable parameters in a smooth model, may be used to gain insight into an alternative distribution.
Robust Estimating Functions and Bias Correction for Longitudinal Data Analysis
Authors: Wang You‐Gan , Lin Xu , Zhu Min
Published: August 2005

SummaryRobust methods are useful in making reliable statistical inferences when there are small deviations from the model assumptions. The widely used method of the generalized estimating equations can be “robustified” by replacing the standardized residuals with theM‐residuals. If the Pearson residuals are assumed to be unbiased from zero, parameter estimators from the robust approach are asymptotically biased when error distributions are not symmetric. We propose a distribution‐free method for correcting this bias. Our extensive numerical studies show that the proposed method can reduce the bias substantially. Examples are given for illustration.
Standard Errors for Attributable Risk for Simple and Complex Sample Designs
Authors: Graubard Barry I. , Fears Thomas R.
Published: August 2005

SummaryAdjusted attributable risk (AR) is the proportion of diseased individuals in a population that is due to an exposure. We consider estimates of adjusted AR based on odds ratios from logistic regression to adjust for confounding. Influence function methods used in survey sampling are applied to obtain simple and easily programmable expressions for estimating the variance of. These variance estimators can be applied to data from case–control, cross‐sectional, and cohort studies with or without frequency or individual matching and for sample designs with subject samples that range from simple random samples to (sample) weighted multistage stratified cluster samples like those used in national household surveys. The variance estimation ofis illustrated with: (i) a weighted stratified multistage clustered cross‐sectional study of childhood asthma from the Third National Health and Examination Survey (NHANES III), and (ii) a frequency‐matched case–control study of melanoma skin cancer.