Developmental failure of the intra-articular ligaments in mice with absence of growth differentiation factor 5

OBJECTIVE

To show the phenotypic characteristics of the knee joints in brachypodism mice (bp mice), which carry a functional null mutation of the growth differentiation factor 5 (GDF5) gene, we investigated the adult and embryonic bp mice.

METHOD

Radiographic and macroscopic examinations of the knee joint of adult bp mice were performed. A histological examination of the knee joint of bp mice from E12.5 to E18.5 was also performed.

RESULTS

Radiographic and macroscopic examinations of the adult bp mice showed anterior dislocation, hypoplastic condyles, and absence of the intra-articular ligaments. Safranin O staining of knee joints of the embryonic bp mice showed severe hypoplasty of the chondroepiphyses and intra-articular ligaments at E16.5. There was no difference in the number and location of 5-bromo-2'-deoxyuridine (BrdU)-positive cells between wild-type and bp mice through E12.5 to E14.5. A terminal deoxynucleotidyltransferase-mediated dUTP nick-end labeling (TUNEL) study showed excessive cell death of mesenchymal cells of the future knee joint in bp mice at E12.5 and E13.5.

CONCLUSION

bp mice exhibit developmental failure of the condyles and intra-articular ligament of the knee joints.

Fetal calf serum-free culture of Chinese hamster ovary cells employing fish serum

The effects of fish serum on cell growth and human granulocyte-macrophage colony-stimulating factor (hGM-CSF) production in an adhesion culture of Chinese hamster ovary (CHO) cells DR1000L4N were investigated and compared with those of fetal calf serum (FCS). Although fish serum did not stimulate the initial adhesion of CHO cells to culture dishes, it prompted cell growth after cell adhesion with FCS for 24 h. The cell density in the fish serum medium reached 75% that in the FCS medium. Fish serum promoted cell adhesion to and cell growth on collagen-coated dishes. The cell-specific production rate of hGM-CSF in the fish serum medium on collagen-coated dishes was almost the same as that in the FCS medium.

Effects of temperature on the immature development of the stone leek leafminer Liriomyza chinensis (Diptera: Agromyzidae)

The effect of nine constant temperatures (15, 17.5, 20, 22.5, 25, 27.5 30, 32.5, and 35 degrees C) on the development of the stone leek leafminer, Liriomyza chinensis (Kato), on Japanese bunching onion, Allium fistulosum L., was studied in the laboratory. Developmental times for immature stages were inversely proportional to temperature between 15 and 30 degrees C but increased at 32.5 degrees C. Total developmental times from egg to adult emergence decreased from 69.6 to 17.1 d for temperatures from 15 to 30 degrees C, with pupae requiring more time for development than the combined egg and larva stages. Both linear and nonlinear (Logan equation VI) models provided a reliable fit of development rates versus temperature for all immature stages. The lower developmental thresholds that were estimated from linear regression equations for the egg, first, second, and third instars, total larva, egg-larval, pupa, and total combined immature stages were 12.1, 10.6, 13.6, 8, 9.6, 11.3, 11.2, and 11.4 degrees C, respectively. The degree-day accumulation was calculated as 312.5 DD for development from egg to adult emergence. By fitting the nonlinear models to the data, the upper and optimal temperatures for egg, larva, pupa, and total immature stages were calculated as 37.8 and 31.7, 34.9 and 30.1, 35.8 and 30.6, and 35.0 and 30.9 degrees C, respectively. These data are useful for predicting population dynamics of L. chinensis under field conditions and determining the maximum proportion of susceptible individuals for facilitating improved timing of application of control measures.

Thrombin induces striatal neurotoxicity depending on mitogen-activated protein kinase pathways in vivo

Intracerebral hemorrhage represents stroke characterized by formation and expansion of hematoma within brain parenchyma. Blood-derived factors released from hematoma are considered to be involved in poor prognosis of this disorder. We previously reported that thrombin, a blood-derived serine protease, induced cytotoxicity in the cerebral cortex and the striatum in organotypic slice cultures, which depended on mitogen-activated protein kinase (MAPK) pathways. Here we investigated the mechanisms of thrombin cytotoxicity in the striatum in vivo. Thrombin microinjected into the striatum of adult rats induced neuronal death and microglial activation around the injection site. Neuronal loss without any sign of nuclear fragmentation was observed as early as 4 h after thrombin injection, which was followed by gradual neuronal death exhibiting nuclear fragmentation. Thrombin-induced damage assessed at 72 h after injection was partially but significantly reduced by concomitant administration of inhibitors of MAPK pathways. Activation of extracellular signal-regulated kinase (ERK) and p38 MAPK in response to thrombin was verified by Western blot analysis. Moreover, phosphorylated ERK and p38 MAPK were localized prominently in reactive microglia, and inhibition of microglial activation by minocycline attenuated thrombin-induced damage, suggesting that reactive microglia were responsible for thrombin-induced neuronal death. Thus, MAPK pathways and microglial activation may serve as therapeutic targets of pathogenic conditions associated with hemorrhagic stroke.

Quantitative analysis of messenger RNA expression of matrix metalloproteinases (MMP-2 and MMP-9), tissue inhibitor-2 of matrix metalloproteinases (TIMP-2), and steroidogenic enzymes in bovine placentomes during gestation and postpartum

The relationship between the mRNA expression of proteolytic and steroidogenic enzymes in bovine placentomes was examined. Caruncle and cotyledon tissues were collected every 6 hr after spontaneous parturition until the fetal membranes were released. Based on the time of fetal membrane release after parturition, the specimens were classified as follows: (1) the early group, in which the fetal membranes were released within 6 hr after parturition; and (2) the late group, in which the fetal membranes were released 6-12 hr after parturition. The placentomes from a slaughterhouse were additionally collected as samples for the examination of enzymes during the gestation period. The mRNA expression of steroidogenic enzymes in the cotyledon was observed to be higher than that in caruncle tissues; however, the mRNA expression patterns of P450scc and StAR tended to be similar in both placental tissues. On the other hand, although the expression levels of TIMP-2 mRNA in both caruncle and cotyledon tissues were similar, during gestation and postpartum the expression levels of MMP-2 and MMP-9 mRNA were approximately 10 times higher in caruncle than in cotyledon tissue. Marked contrasting changes in mRNA expression patterns between pre- and postpartum periods were observed for MMP-2 and MMP-9 in caruncle tissues and for MMP-9 and TIMP-2 in cotyledon tissues. The present study provides the first evidence that MMP-2, MMP-9, and TIMP-2 mRNAs are expressed in bovine placentomes during the gestational and postpartum periods and suggests that these enzymes, in conjunction with steroidogenic enzymes, mediate fetal membrane detachment after parturition.

Gene silencing by the tRNA maturase tRNase ZL under the direction of small-guide RNA

We have been developing a unique system for the downregulation of a gene expression through cutting a specific mRNA by the long form of tRNA 3'-processing endoribonuclease (tRNase Z(L)) under the direction of small-guide RNA (sgRNA). However, the efficacy of this system and the involvement of tRNase Z(L) in the living cells were not clear. Here we show, by targeting the exogenous luciferase gene, that the efficacy of the sgRNA/tRNase Z(L) method can become comparable to that of the RNA interference technology and that the gene silencing is owing to tRNase Z(L) directed by sgRNA not owing to a simple antisense effect. We also show that tRNase Z(L) together with sgRNA can downregulate expression of the endogenous human genes Bcl-2 and glycogen synthase kinase-3beta by degrading their mRNAs in cell culture. Furthermore, we demonstrate that a gene expression in the livers of postnatal mice can be inhibited by an only seven-nucleotide sgRNA. These data suggest that sgRNA might be utilized as therapeutic agents to treat diseases such as cancers and AIDS.

Serum adiponectin and leptin in a patient with Cushing's syndrome before and after adrenalectomy

We measured the serum adiponectin and leptin concentrations before and after successful removal of a left adrenal adenoma in a 46-year-old woman with Cushing's syndrome. The serum adiponectin level was 6.0 microg/ml before the operation and rose to 8.1 microg/ml after adrenalectomy. However, the serum leptin level was markedly high (24.8 ng/ml) before the operation and decreased to within the normal range (6.0 ng/ml) 6 months after adrenalectomy, concomitant with weight reduction and normalization of the serum cortisol level.

Effect of NOS inhibitor on cytokine and COX2 expression in rat pulpitis

Various kinds of chemical mediators are synthesized in the course of pulpitis; thus, control of their production would assist in inducing a reduction in pulpal inflammation. We hypothesized that nitric oxide (NO) would be an important mediator of pulpal inflammation. Pulpal inflammation was induced by the application of LPS in rat incisor pulp, and inducible nitric oxide synthase (iNOS) expression was evaluated by reverse-transcription/polymerase chain-reaction and immunohistochemical staining. After LPS application, iNOS mRNA was first detected after 3 hrs, peaked at 6 hrs, and decreased thereafter. iNOS-positive cells were macrophages and neutrophils. An NOS inhibitor caused drastic decreases in the expression of pro-inflammatory cytokines and COX2 mRNA, which was highly induced in the LPS-induced pulpitis. These results indicate that NO synthesis is related to the initiation of mediator production, and that its down-regulation should contribute to the prevention of pro-inflammatory mediator synthesis.

Introduction of air in the anaerobic culture of Streptococcus pneumoniae serotype 23F induces the release of capsular polysaccharide from bacterial surface into the cultivation medium

AIM

An approach to increase Streptococcus pneumoniae capsular polysaccharide (CPS) in the culture medium during fed-batch cultivation in bioreactor.

METHODS AND RESULTS

Streptococcus pneumoniae serotype 23F was cultivated in a 5-l bioreactor with nitrogen-sparging and followed by addition of air in the stationary phase. The amount of CPS released in the supernatant progressively increased under air sparging. The profile of cellular viability and optical density was similar in both cultures. Immunoelectron microscopy showed that the amount of tightly cell-bound CPS was higher in bacteria cultivated under nitrogen than under air.

CONCLUSIONS

The stress caused by the addition of air at the stationary phase promoted a large increase of free CPS into the medium, as a consequence of the morphologic change in the capsule.

SIGNIFICANCE AND IMPACT OF THE STUDY

The use of air in the stationary phase of the culture would greatly simplify the subsequent downstream process, allowing CPS purification from the supernatant. The direct consequence of this process improvement is the reduction of vaccine production costs.

Primary erythrocytosis in a Japanese black calf: a case report

An 8-month-old Japanese Black heifer with severe erythropoietic symptoms was subjected to clinical, histological and cytological examinations. During the 1 month clinical observation period, severe increases in RBC count, packed cell volume and haemoglobin concentration were observed. The plasma erythropoietin (Epo) concentration of the heifer (20.7 mIU/ml) was similar to that observed in normal control heifers. Blood gas examinations of the arterial and venous blood revealed low levels of partial pressure O(2) (PaO(2)), partial pressure CO(2) (PaCO(2)) and O(2) saturation (SaO(2)), while the blood pH was within the normal range. Gross lesions could not be detected. However, microscopic observation revealed severe proliferation of erythroblasts in the bone marrow and in the spleen without evidence of neoplastic changes. Based on these clinical and pathological examinations, we diagnosed the heifer as being the first case of primary erythrocytosis in Japanese Black cattle.

New HSN2 mutation in Japanese patient with hereditary sensory and autonomic neuropathy type 2

The authors report a Japanese patient with hereditary sensory and autonomic neuropathy type 2 (HSAN2) who has a new mutation of the HSN2 gene. The pathologic findings of the patient matched those of Canadian patients. They identified a homozygous 1134-1135 ins T mutation, resulting in a frameshift, and the subsequent premature stop codon at residue 378. These observations support the hypothesis that HSN2 is a causative gene for HSAN2.

Alteration of product specificity of cyclodextrin glucanotransferase from Thermococcus sp. B1001 by site-directed mutagenesis

Cyclodextrin glucanotransferase (CGTase) from the hyperthermophilic archaeon Thermococcus sp. B1001 catalyzed the production predominantly of alpha-cyclodextrin (CD) from starch (Tachibana, Y. et al., Appl. Environ. Microbiol., 65, 1991-1997, 1999). The CGTase gene (cgtA) from this strain was cloned and sequenced. It was composed of 2217 nucleotides, and encoded a protein (739 amino acids) with a molecular mass of 83,240 Da. Recombinant CgtA expressed in Escherichia coli also catalyzed the production predominantly of alpha-CD from starch, as did native CgtA from strain B1001. Based on a substrate binding model of Bacillus circulans no. 8 CGTase, Tyr100, Trp191 and Tyr267 were specified to locate the spiral amylose and to minimize the size of the CD by saccharide aromatics interaction. In order to determine the critical residue for catalyzing production predominantly of alpha-CD, site-directed mutations were introduced in CgtA (Y100W, Tyr100-->Trp; W191Y, Trp191-->Tyr; W191F, Trp191-->Phe; Y267W, Tyr267-->Trp; Y267F, Tyr267-->Phe). Analysis of the reaction products by HPLC revealed that the mutant enzyme Y267W produced more beta- and gamma-CD than the wild-type enzyme. However, the other mutants still produced high levels of alpha-CD, suggesting that Tyr267 plays a critical role in alpha-CD production catalyzed by B1001 CGTase.

Effects of high concentrations of energy sources and metabolites on suspension culture of Chinese hamster ovary cells producing tissue plasminogen activator

A high-concentration medium was developed for the high-density cultivation of Chinese hamster ovary (CHO) cells to produce tissue plasminogen activator (tPA). First, the effects of the concentrations of several medium components on the growth and metabolism of CHO cells were studied particularly in relation to the serum concentration, in order to develop a suitable concentrated medium. High concentrations of serum, glucose, lactate, and glutamine and a low ammonia concentration increased the specific growth rate and decreased the specific tPA production rate. Among these components, the effect of the serum concentration was the most significant. There was an inverse correlation between the specific rates of cell growth and tPA production. Using a medium containing glutamine at twice the concentration of the original medium (F-12) allowed the medium volume to be reduced to seven-ninths that of the original, without any reduction in tPA productivity. When the F-12 medium was supplemented five-fold with amino acids and vitamins, the total amount of tPA produced, specific rate of tPA production, and yield of tPA per unit volume of medium employed were respectively enhanced 1.7, 1.5, and 3.6 times. As a consequence, the frequency of medium exchange could be reduced. The results strongly indicate that the supplementation of nutrient amino acids and vitamins to a medium with a low concentration of serum are the most critical factors for cost-effective tPA production in high-density cell cultivation.

Effect of polyamines on histone-induced DNA compaction of hyperthermophilic archaea

The effect of polyamines on histone-mediated DNA compaction was examined in vitro with archaeal histone HpkA from Pyrococcus kodakaraensis KOD1. An agarose gel mobility-shift experiment indicated that histone-bound DNA (compacted DNA) was further compacted by addition of a polyamine (putrescine, spermidine, or spermine) or its acetylated form (N-acetylputrescine, N1-acetylspermidine, N8-acetylspermidine, or N1-acetylspermine) when the mixture was incubated at above 75 degrees C. Spermine was most effective in compaction enhancement among all the polyamines tested. A high concentration of potassium ion (1.0 M) did not stabilize the compacted form of DNA even though double-stranded DNA was stably maintained against thermal denaturation at elevated temperatures under this condition. It appears likely that multivalent polyamines have a nucleosome maintenance function in hyperthermophilic archaea in high-temperature environments.

Effect of antioxidants on the apoptosis of CHO cells and production of tissue plasminogen activator in suspension culture

The effects of antioxidants on the apoptosis of Chinese hamster ovary (CHO) 1-15,500 cells and production of tissue plasminogen activator (tPA) in suspension culture were investigated. After cell growth to 2 x 10(5) cells/ml in Ham's F12 medium containing 10% newborn bovine serum (NBS) in a spinner bottle, CHO cells were maintained for 6 d in Ham's F12 medium containing 0 or 0.4% NBS and 10 mM antioxidants, namely, l-ascorbic acid 2-phosphate (VCP) or the reduced form of glutathione (GSH). The viable cell concentrations at day 6 in the serum-free culture with GSH and in the low-serum culture wiht VCP or GSH were 0.57, 1.04 and 1.69 x 10(5) cells/ml, respectively, while those in the serum-free and low-serum cultures without the antioxidants were only 2.33 and 1.17 x 10(3) cells/ml, respectively. The percentages of apoptotic cells in the serum-free and low-serum cultures with VCP (73.2, 44.6%) and GSH (76.9, 38.6%) measured using a flowcytometer after annexin V-FITC/propidium iodide staining were markedly lower than those in the cultures without antioxidants (96.3, 92.5%). The percentage of cells having a high mitochondrial membrane potential among the viable cells in the cultures with antioxidants determined using a flowcytometer after 5,5',6,6'-tetrachloro-1,1',3,3'-tetraethylbenzimidazolylcarbocyanine iodide staining was clearly higher than those in the cultures without the antioxidants. The production of tPA in the serum-free and low-serum media with VCP (0.282, 2.92 mg/l) or GSH (1.01, 1.61 mg/l) was markedly higher than that in the cultures without the antioxidants (0.275, 0.689 mg/l). Consequently, the suppression of apoptosis through the maintenance of the membrane potential of mitochondria by VCP or GSH resulted in a marked increase in tPA production by CHO cells in the serum-free and low-serum cultures.

Characterization of FtsZ homolog from hyperthermophilic archaeon Pyrococcus kodakaraensis KOD1

The gene of bacterial type ftsZ homolog in hyperthermophilic archaeon, Pyrococcus kodakaraensis KOD1 (Pk-ftsZ), was identified. The gene product of the Pk-ftsZ gene is composed of 380 amino acids with a molecular mass of 41,354 Da. In the deduced amino acid sequence of the Pk-ftsZ gene, a glycine-rich sequence (Gly-Gly-Gly-Thr-Gly-Ala-Gly) implicated in GTP binding was well conserved. The Pk-ftsZ gene was overexpressed using Escherichia coli as a host and the recombinant protein was purified. The purified Pk-FtsZ protein exhibited GTPase activity with optimum temperatures higher than 80 degrees C. However, the protein showed little GTPase activity at 40 degrees C, indicating that a high reaction temperature is required for the GTPase activity in accordance with the thermophilic nature of P. kodakaraensis KOD1. The GTP-binding ability of Pk-FtsZ protein could also be detected by UV-induced cross-linking of a protein to [alpha-32P] GTP. The Pk-ftsZ gene was expressed in E. coli cells with a temperature-sensitive ftsZ mutation, E. coli ftsZ84 (ts), but its mutant phenotype of elongated cell form at a nonpermissive temperature (42 degrees C) could not be compensated, possibly because of the thermophilic nature of the Pk-FtsZ. Pk-FtsZ could form protofilaments in a GTP-dependent manner at 90 degrees C. Results of phylogenetic analysis suggest that there might be additional factors required for formation of the Z ring in P. kodakaraensis KOD1.

Enhanced signal transduction by a directly fused protein of interleukin-6 and its receptor

In order to develop a new type of agonist for the interleukin 6 (IL-6) signal, the gene encoding a directly fused protein (DFP) was constructed by joining the N-terminal portion of IL-6 and the C-terminal (soluble) portion of IL-6R (sIL-6R) without using a flexible polypeptide linker. The biological activity if DFP from a recombinant Pichia pastoris was examined by growth stimulation of IL-6-dependent BAF130 cells expressing human gp130, a membrane receptor. The recombinant DFP exhibited a much stronger growth stimulation (10 times) than the independent IL-6 and sIL-6R (IL-6/sIL-6R), mainly because association of the IL-6 and IL-6R could be maintained even at lower concentrations of DFP. Surface plasmon resonance (SPR) analysis showed that DFP bound to the extracellular portion of gp130 in the biphasic mode, and the dissociation constants of DFP for two phases were the same as those of IL-6/sIL-6R. In cells treated with DFP, stimulation of Stat3 phosphorylation was maintained for a longer period (150 min) than in cells treated with IL6/Il-6R, suggesting that the signal mediated by the DFP was more durable than that mediated by IL-6/sIL-6R, although the signal transduction mechanisms are almost the same for both DFP and IL-6/IL-6R. Therefore, the stronger activity of DFP was attributed to the maintained association of its subunits and/or prolonged phosphorylation of Stat3.

Selective retension of active cells employing low centrifugal force at the medium change during suspension culture of Chinese hamster ovary cells producing tPA

The effect of centrifugal force applied for cell separation at the medium change on the growth, metabolism and tissue plasminogen activator (tPA) productivity of Chinese hamster ovary (CHO) cells suspension culture was investigated. The viability of the precipitated cells increased exponentially as the centrifugal force decreased. However, the cell recovery was lower than 91% when centrifugal forces applied for 5 min was less than 67 x g. In cultures incubated for 474 h with 7 medium changes employing centrifugal forces ranging from 67 to 364 x g, a centrifugal force lower than 119 x g resulted in higher specific rates of growth, glucose consumption, and lactate and tPA production during the whole culture period. On the other hand, daily centrifugation at 67 to 537 x g without discarding the supernatant had no effect on the specific rates. The cultures inoculated with cells precipitated at a centrifugal force of 67 x g showed apparently higher specific rates of metabolism compared to those inoculated with cells in the supernatant. The cells in the supernatant and the precipitate obtained following centrifugation at 67 x g have average diameters of 15.5 and 17.4 microm, respectively. The intracellular contents of amino acids, especially nonessential amino acids, of the precipitated cells were markedly higher than those of the cells in the supernatant. These results indicate that large cells with high amino acid content and metabolic activity were selectively retained in the culture by means of centrifugation at low forces such as 67 x g. Consequently, application of a low centrifugal force is recommended for medium change in order to maintain higher specific productivity of suspended mammalian cells in perfusion culture.

Unique nucleoid structure during cell division of Thermococcus kodakaraensis KOD1

The nucleoid structure and the partition in the hyperthermophilic archaeon Thermococcus kodakaraensis KOD1 were observed by a combination of phase-contrast microscopy and fluorescence microscopy. The nucleoids occurred as rounded fluorescent foci centrally located in the cells and as differences in fluorescence intensity between exponential and stationary phases. The cellular space occupied by the nucleoid in the stationary phase was larger than that in the exponential phase. Various shapes of nucleoid in the exponential-phase cells were observed, indicating that nucleoid separation was processed under cell cycle control. The number of cells which showed distinctive division stages was counted and the proportions of dividing cells were determined. About half of the observed cells were in the replication stage. More than 40% of the counted cells possessed a fully replicated but not separated form of nucleoid. Only 8% of the total cells clearly showed visible constriction. These results suggested that the post-replication period before cell division was relatively as long as the eucaryal gap period (G2); however, the period of visible cell constriction was almost the same as that of the bacteria.

Gene analysis and enzymatic properties of thermostable beta-glycosidase from Pyrococcus kodakaraensis KOD1

A beta-glycosidase with broad substrate specificity was identified from a hyperthermophilic archaeon, Pyrococcus kodakaraensis KOD1. The gene encoding beta-glycosidase (Pk-gly) consists of 1449 nucleotides corresponding to a polypeptide of 483 amino acids. The protein showed similarity with other beta-glycosidases from family-1 glycosyl hydrolases, in particular, it showed high identity to beta-mannosidase from P. furiosus (55.7%), beta-glycosidase from Sulfolobus solfataricus (42.7%) and beta-glucosidase from P. furiosus (41.9%). The cloned gene was expressed in Escherichia coli and the recombinant protein was purified. The beta-glycosidase showed optimal activity at pH 6.5 and at an extremely high temperature of 100 degrees C, and had a half-life of 18 h at 90 degrees C. The beta-glycosidase hydrolyzed various pNp-beta-glycopyranosides, with kcat K(m) values in the order of pNp-beta-glucopyranoside = pNp-beta-mannopyranoside > pNp-beta-galactopyranoside > pNp-beta-xylopyranoside. pNp-beta-mannopyranoside was the substrate exhibiting the lowest K(m) value [0.254 mM] with a kcat K(m) ratio comparable to that of pNp-beta-glucopyranoside. This substrate specificity was distinct from previously reported beta-glycosidases. We observed that the region in PK-Gly corresponding to the fifth alpha-helix and beta-strand region of beta-glycosidase from S. solfataricus, which constitutes a large portion of the channel for substrate incorporation, displayed a chimeric structure, with the N-terminal region similar to beta-glycosidases and the C-terminal region similar to beta-mannosidases. An exo-type hydrolytic activity and transglycosylation activity were also observed towards cellooligomers.

Acute improvement of atrial mechanical stunning after electrical cardioversion of persistent atrial fibrillation: comparison between biatrial and single atrial pacing

OBJECTIVE

To evaluate the acute effects of atrial pacing at different pacing sites on mechanical stunning after cardioversion of atrial fibrillation (AF).

SETTING

Tertiary referral centre.

PATIENTS

20 patients with persistent AF were studied.

INTERVENTIONS

Spontaneous echo contrast (SEC), left atrial appendage emptying velocity (LAAEV), and left atrial appendage emptying fraction (LAAEF) were assessed by transoesophageal echocardiography (TOE) during AF, after conversion to sinus rhythm, and during atrial pacing from the right atrial appendage, left lateral atrium, and both atria simultaneously. Transmitral inflow velocity of the atrial wave (TMIF-A) by TOE and the maximum P wave duration in 12 lead ECG were also measured during sinus rhythm and atrial pacing.

MAIN OUTCOME MEASURES

Comparison of atrial mechanical function and P wave duration in 12 lead ECG during atrial pacing from different sites after cardioversion of AF.

RESULTS

Compared with sinus rhythm, atrial pacing at 80 beats/min increased LAAEV from mean (SD) 14.6 (10.1) to 33.4 (19.8) cm/s (p = 0.001), LAAEF from 13.8 (8.5) to 32.1 (11.2)% (p < 0.001), and TMIF-A from 24.6 (11.9) to 45.6 (21.0) cm/s (p < 0.001) and reduced SEC grade from 2.6 (1.0) to 1.6 (0.9) (p < 0.001). These effects had a positive force-frequency relation. Biatrial pacing produced the shortest P wave duration and resulted in the most significant improvement in atrial function (LAAEV, 33.2 (19.3) v 53.7 (23.9) cm/s, p = 0.0001; LAAEF, 31.9 (11.1) v 46.2 (12.6)%, p < 0.0001; TMIF-A, 37.7 (18.3) v 54.1 (21.2) cm/s, p < 0.001; SEC grade, 1.4 (1.1) v 0.8 (0.9), p = 0.001, right atrial appendage versus biatrial pacing).

CONCLUSIONS

Atrial pacing at increased rates can improve atrial mechanical function after cardioversion of persistent AF. Biatrial pacing may be the most effective technique to reverse atrial mechanical stunning.