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Biomedical subjects

H Yin

Publications and source records attributed to H Yin.

At least 127 records · Page 7Linked to original sources
PubMed1997

Theileriosis of sheep and goats in China.

Theileriosis is an important disease of sheep and goats in West China. Its main distribution includes Qinghai, Gansu, Ningxia, Inner Mongolia, Shaanxi and Sichuan. The epidemic period is from late March to July with April-May being the peak months. This is the period of most intensive tick attack by Haemaphysalis qinghaiensis (77.2-99.24%) during the year. It has been proved that the nymphs and adults, which develop from larvae and nymphs engorged on infected sheep or goats can transmit the pathogen. Experimental infections revealed the incubation period, clinical signs and the pathogen's morphological characteristics. The disease was more serious in lambs and exotic adult animals than native adult animals. The sickness rates of lambs, exotic and native adult animals were 78-85%, 41% and 9% respectively; death rates were 81.41%, 62.5% and 65% respectively. Clinical prophylaxis, chemical therapy and destruction of ticks have been carried out with antiparasitic compounds to control the disease since 1982. Experiments demonstrated that the curative rate was up to 76-86%, but no satisfactory prophylactic methods were found.

Animals↗
PubMed1997

Babesiosis in China.

The importance of babesiosis in livestock in China is discussed and mainly focused on bovine and equine babesiosis. Babesiosis is still one of the most important diseases affecting livestock and has caused great economic loss. Nine species of Babesia have been recognized in livestock: B. bigemina, B. bovis, B. major, B. motasi, B. ovis, B. perroncitoi, B. trautmanni, B. equi (Theileria equi), B. caballi. The distribution of Babesia follows the distribution of the tick vectors. The main vectors of bovine babesiosis are the one-host tick Boophilus microplus and the three-host ticks Rhipicephalus haemaphysaloides haemaphysaloides, Haemaphysalis punctata and Haemaphysalis longicornis. Bovine babesiosis has caused significant losses in milk and meat from cattle in most parts of China. The disease is also a barrier to improving productivity of local cattle by cross-breeding due to the high mortality of genetically superior but highly susceptible cattle, especially dairy cattle, imported from Babesia-free areas. Dermacentor nuttalli is the major vector of equine babesiosis and the tick is distributed in almost all parts of North China. Outbreaks of equine babesiosis have not been very common, but in some districts the disease has seriously affected horses, donkeys and mules.

Animals↗
PubMed1997

Attempted transmission of Babesia major by Boophilus microplus.

Two experiments was carried out to determine if Babesia major could be transmitted by Boophilus microplus. In experiment 1, a Babesia-free batch of laboratory reared Bo. microplus larvae were applied to an intact calf infected by inoculation with a B. major stabilate. The calf showed a B. major parasitaemia while the larvae, nymphs and adult ticks were engorging. The engorged females were cultured and batches were incubated at one of the three following temperatures: 24, 28 or 32 degrees C. Approximately 10,000 larvae derived from each of the females were used to infest each of three splenectomized calves. In experiment 2, Babesia-free Bo. microplus larvae were applied to a splenectomized calf; the calf was injected with B. major stabilate and showed a B. major parasitaemia during the adult stage of tick development. The engorged females were incubated at room temperature and the resulting larvae (approximately 10,000) were used to infest a splenectomized calf. Examination of blood films for the presence of B. major from the four calves infested by the second generation larvae in the two experiments were negative.

Animals↗
PubMed1997

Stretching DNA with optical tweezers.

Force-extension (F-x) relationships were measured for single molecules of DNA under a variety of buffer conditions, using an optical trapping interferometer modified to incorporate feedback control. One end of a single DNA molecule was fixed to a coverglass surface by means of a stalled RNA polymerase complex. The other end was linked to a microscopic bead, which was captured and held in an optical trap. The DNA was subsequently stretched by moving the coverglass with respect to the trap using a piezo-driven stage, while the position of the bead was recorded at nanometer-scale resolution. An electronic feedback circuit was activated to prevent bead movement beyond a preset clamping point by modulating the light intensity, altering the trap stiffness dynamically. This arrangement permits rapid determination of the F-x relationship for individual DNA molecules as short as -1 micron with unprecedented accuracy, subjected to both low (approximately 0.1 pN) and high (approximately 50 pN) loads: complete data sets are acquired in under a minute. Experimental F-x relationships were fit over much of their range by entropic elasticity theories based on worm-like chain models. Fits yielded a persistence length, Lp, of approximately 47 nm in a buffer containing 10 mM Na1. Multivalent cations, such as Mg2+ or spermidine 3+, reduced Lp to approximately 40 nm. Although multivalent ions shield most of the negative charges on the DNA backbone, they did not further reduce Lp significantly, suggesting that the intrinsic persistence length remains close to 40 nm. An elasticity theory incorporating both enthalpic and entropic contributions to stiffness fit the experimental results extremely well throughout the full range of extensions and returned an elastic modulus of approximately 1100 pN.

DNA↗
PubMed1997

Structure and genomic organization of a novel human endogenous retrovirus family: HERV-K (HML-6).

Prototypic elements of a novel human endogenous retrovirus (HERV) family were identified and cloned from a human genomic library by the use of a pol fragment, HML-6, related to type A and type B retroviruses and class II HERVs. Out of 39 polhybridizing clones, five contained structures of full-length retroviral proviruses, with regions showing similarity to gag, pol and env, flanked by long terminal repeats (LTRs). Restriction mapping and partial sequence analysis of each full-length clone revealed few conserved restriction sites among HML-6 genomes, and about 20% sequence divergence over the reverse transcriptase region sequenced, suggesting that HML-6 constitutes a heterogeneous, but distinct family of elements belonging to the HERV-K superfamily. Sequence analysis of two clones, HML-6p and HML-6.17, revealed a lysine (K) tRNA UUU primer-binding site, and 40-68% nucleotide sequence similarity to LTR, gag, pro, pol and env regions of type B retroviruses and class II HERVs. HERV-K (HML-6) elements are present at about 30-40 copies per haploid genome. The HML-6 LTRs contain putative progesterone-responsive elements, which may be involved in the regulation of HML-6 expression. Furthermore, there are about 50 additional solitary HML-6 LTRs per haploid genome. Such LTRs were integrated within the pol region of two clones belonging to the same HML-6 family, indicating that some site preference may be involved in HERV integration.

Amino Acid Sequence↗
PubMed1997

Actions of lidocaine on reentrant ventricular rhythms in the subacute myocardial infarction period in dogs.

The actions of lidocaine were studied in 18 dogs, 4 days after ligation of the left anterior descending artery, by computerized mapping. Lidocaine only occasionally suppressed the induction of reentry. At fast heart rates, lidocaine actually facilitated the induction of reentry. The effects on conduction and refractoriness of normal and ischemic myocardium were measured using high-resolution techniques. Lidocaine promoted reentry by a rate-dependent increase in refractory gradient, resulting in additional block, and a selective decrease in conduction velocity in ischemic tissue, resulting in additional conduction delay. Lidocaine could prevent reentry through a rate-independent differential increase in refractory period gradient at the entrance to the common pathway of the circuit, causing block of the reentrant impulse. We conclude that the proarrhythmic effect of lidocaine is due to increased conduction delay and block while the antiarrhythmic effect is due to block of the reentrant impulse by prolonged refractoriness in the common pathway.

Animals↗
PubMed1997

Rational design of selective ligands for trypanothione reductase from Trypanosoma cruzi. Structural effects on the inhibition by dibenzazepines based on imipramine.

Trypanothione reductase, the enzyme which in trypanosomal and leishmanial parasites catalyses the reduction of trypanothione disulphide to the redox-protective dithiol and has been identified as a potential target for rational antiparasite drug design, has been found to be strongly inhibited by tricyclic compounds containing the saturated dibenzazepine (imipramine) nucleus, with Ki values in the low micromolar range. This drug lead structure was designed by molecular graphics analysis of a three-dimensional homology model, focussing on the active-site. Inhibition studies were carried out to determine the effect of inhibitor structure on the inhibitory strength towards recombinant trypanothione reductase from Trypanosoma cruzi. Hansch analysis showed that inhibitory strength depended on terms in pi, pi 2 and sigma m indicating dependence on both lipophilicity and inductive effect for ring-substituted analogues of imipramine. The side-chain omega-aminoalkyl chain had to be longer than 2-carbon units for inhibition. The effect on inhibition strength of the substituent at the omega-amino position on the side-chain of the central ring nitrogen atom depended markedly on the detailed substitution pattern of the rest of the molecule. This provides kinetic evidence studies of multiple binding modes within a single, blanket binding site for the inhibitor with the tricyclic ring system in the general region of the hydrophobic pocket lined by Trp21, Tyr110, Met113 and Phe114. This aspect of the structural sensitivity of the precise active-site triangulation adopted by the inhibitor is probably a function of the use of hydrophobic interactions of low directional specificity in this pocket combined with an electrostatic anchoring by the omega-N+ HMe2 function of the inhibitor, presumably with a glutamate side-chain, such as Glu-18, Glu-466' and/or Glu-467'.

Animals↗
PubMed1997

[The effects of IFN-gamma on the antitumor abilities of immunocytes and chemotherapeutic agents].

We studied the effects of IFN-gamma in immunotherapy and chemoimmunotherapy. The effects of IFN-gamma on TIL and LAK cytotoxicities on K562 tumor cell line and MKN45 gastric cancer tumor were observed. The antitumor effects of 5 chemotherapeutic agents with or without IFN-gamma on SGC7901 gastric cancer cell line were evaluated. The results showed that: (1) IFN-gamma obviously enhanced the cytotoxicities of TIL and LAK on 2 cell line: (2) IFN-gamma also increased the antitumor abilities of 5 agents on SGC7901 cell line. The study suggested that IFN-gamma is useful in immunotherapy and chemoimmunotherapy as an important immunomodulating agent.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1997

[Transfection and expression of human thrombopoietin cDNA for treatment of thrombocytopenia in mice].

OBJECTIVES: To explore that COS-7 cells efficiently transfected with human thrombopoietin (hTPO) cDNA from fetal liver and hTPO potentially treated carboplatin-induced thrombocytopenia in mice. METHODS: Using molecular cloning technique, expression vectors PCIneo under the control of SV40 early. Applying liprofectin mediating method, recombinant plasmids PCIneo-hTPO were transfected into COS-7 cells in addition to effect of G418. After hTPO cDNA and mRNA in colony COS-7 cells were respectively identified by PCR-Southern and dot blot, hTPO was analysed with sandwich ELISA and administrated intraperitoneally to mice with thrombocytopenia. RESULTS: COS-7 cells transfected with constructed PCIneo-hTPO expressed and secreted hTPO up to 48.28 ng/ml in the supernatant. We kinetically observed that the number of megakaryocyte-colony-forming unit (CFU-MK) in bone marrow enhanced to threefold (P < 0.01), especially the number of small CFU-MK, accompanied by an increased mean megakaryocyte volume (P < 0.01) and circulating platelets returned to a normal level (80 +/- 26, x 10(9)/L, P < 0.01) in peripheral blood. CONCLUSION: Recombinant PCIneo-hTPO can efficiently be transfected into COS-7 cells and hTPO is an effective cytokine for treating carboplatin-induced thrombocytopenia in mice.

Animals↗
PubMed1996

Experiments on the transmission of Babesia major and Babesia bigemina by Haemaphysalis punctata.

Experiments on the transmission by Haemaphysalis punctata of three large Babesia strains were carried out. Three Babesia-free batches of laboratory reared H. punctata ticks were infected with two strains of Babesia major, B. major (Xingjiang strain), isolated with adult ticks of H punctata and B. major (Henan strain), isolated with H. longicornis) and a strain of Babesia bigemina by feeding them on the calves infected by inoculation of blood stabilates. H. punctata was shown to be capable of transmitting the B. major strains transovarially. The larvae, nymphs and adults developed from female ticks engorged on the calf infected with B. major (Xingjiang strain) transmitted the pathogen to splenectomised calves with prepatent periods of 15, 11 and 12 days, respectively. The calves infested with larvae and nymphs died of babesiosis with parasitemias of 400 and 710 per 1000 erythrocytes. The calf infested with adult ticks survived babesiosis, but the number of erythrocytes and the amount of haemoglobin were reduced greatly. H. punctata transmitted B. major (Henan strain) in the same way. The prepatent periods of the calves infested with larvae, nymph and adult ticks were 9, 10 and 12 days, respectively. Calves infested with larvae survived, but those infested with nymphal and adult ticks died of babesiosis with parasitemias of 410 and 100 per 1000 erythrocytes, respectively. H. punctata ticks did not transmit the B. bigemina strain to splenectomised calves. There were no clinical symptoms and no parasites were discovered in the blood films during a 2 month observation period after the calves were infested with larval, nymphal and adult ticks derived from female ticks engorged on calves inoculated with B. bigemina.

Animals↗
PubMed1996

Differential expression of human endogenous retroviral sequences similar to mouse mammary tumor virus in normal peripheral blood mononuclear cells.

Mouse mammary tumor virus (MMTV) is a retrovirus that causes breast cancer in certain strains of mice. In a previous study we identified, by sequencing clones from human lymphocytes, six groups with similarities to MMTV. Using a primer pair derived from pol sequences conserved within types A, B, and D retroviruses and probes from the six human MMTV-like (HML-1 to HML-6) groups in an internally controlled hybridization assay we investigated the normal variation of expression in PBMCs. Variations occurred within all groups but was most significant within group HML-1, where hybridization signals differed by more than 500-fold between individuals. Groups HML-2 and HML-3 showed consistently stronger hybridization signals than groups HML-1 and HML-5, while group HML-6 resulted in weak signals for all individuals. Stringent hybridization of the amplified cDNA to 20 individual HML clones also demonstrated a marked heterogeneity of expression. Hybridization signals from some groups and sequences were found to be correlated, either in a positive or negative fashion. RNA isolated from PBMCs collected from two donors at four different time points (in the morning and in the afternoon on the same day, repeated 1 week later) was also analyzed using the six hml probes. A small variation in hybridization signals was seen in samples collected on the same day, but a larger difference was observed in samples taken 1 week later. The correlations and the differences in the expression of HMLs between individuals implicate a complex transcriptional regulation system of these sequences.

Adult↗
PubMed1996

Tbeta 4 is not a simple G-actin sequestering protein and interacts with F-actin at high concentration.

Thymosin beta 4 is acknowledged as a major G-actin binding protein maintaining a pool of unassembled actin in motile vertebrate cells. We have examined the function of Tbeta 4 in actin assembly in the high range of concentrations (up to 300 micron) at which Tbeta 4 is found in highly motile blood cells. Tbeta 4 behaves as a simple G-actin sequestering protein only in a range of low concentrations (<20 micron). As the concentration of Tbeta 4 increases, its ability to depolymerize F-actin decreases, due to its interaction with F-actin. The Tbeta 4-actin can be incorporated, in low molar ratios, into F-actin, and can be cross-linked in F-actin using 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide. As a result of the copolymerization of actin and Tbeta 4-actin complex, the critical concentration is the sum of free G-actin and Tbeta 4-G-actin concentrations at steady state, and the partial critical concentration of G-actin is decreased by Tbeta 4-G-actin complex. The incorporation of Tbeta 4-actin in F-actin is associated to a structural change of the filaments and eventually leads to their twisting around each other. In conclusion, Tbeta 4 is not a simple passive actin-sequestering agent, and at high concentrations the ability of Tbeta 4-actin to copolymerize with actin reduces the sequestering activity of G-actin-binding proteins. These results question the evaluation of the unassembled actin in motile cells. They account for observations made on living fibroblasts overexpressing beta-thymosins.

Actin Cytoskeleton↗
PubMed1996

Electrophysiological mechanisms of spontaneous termination of sustained monomorphic reentrant ventricular tachycardia in the canine postinfarction heart.

BACKGROUND: The electrophysiological mechanisms of spontaneous termination of sustained monomorphic ventricular tachycardia (SMVT), in the postinfarction heart, generally considered secondary to a reentrant mechanism, have not been fully investigated. METHODS AND RESULTS: Epicardial activation maps of spontaneous termination of 20 different episodes of SMVT (lasting 30 seconds to 10 minutes) from 8 dogs, 4 to 5 days after one-stage ligation of the left anterior descending coronary artery, were analyzed with the use of 254 bipolar electrode recordings with high density (2.5 to 2.8 mm between bipolar electrodes) in the ischemic zone. All ventricular tachycardias (VTs) were due to circus movement reentry with a characteristic figure-8 configuration. Termination always occurred when the two circulating wave fronts blocked in the central common pathway (CCP). Two basic mechanisms of spontaneous termination were observed: (1) In 15 episodes, acceleration of conduction occurred in parts of the reentrant circuit and was associated with slowing of conduction and finally conduction block in the CCP. Acceleration of conduction occurred in the last few cycles of VT both at the outer border of the arcs of functional conduction block in the "normal" myocardial zone and at the pivot points to the entrance to the CCP. When acceleration of conduction was compensated on a beat-to-beat basis by an equal degree of slowing in the CCP, there was no discernible change in the cycle length of the VT in the ECG. In some episodes, the termination of the original reentrant circuit was followed by the development of a different, slower reentrant pathway that lasted for one or a few cycles prior to termination. (2) In 5 VT episodes, the activation wave front in the CCP abruptly broke across a stable arc of functional conduction block, resulting in premature activation of the CCP and conduction block. CONCLUSIONS: Distinct electrophysiological changes always preceded spontaneous termination of stable SMVT. The electrophysiological basis for acceleration of conduction in parts of the reentrant circuit during the last few beats prior to termination and of the abrupt reactivation across a stable arc of block remains to be determined.

Animals↗
PubMed1996

Mechanisms of spontaneous and chemically-induced aneuploidy in mammalian oogenesis: basis of sex-specific differences in response to aneugens and the necessity for further tests.

The basis for sex-specific differences in chemically-induced and age-related aneuploidy of mammalian germ cells is still unknown. We have analysed the maturation of isolated mouse oocytes to characterize the mechanisms underlying drug-induced aneuploidy produced by two compounds, chloral hydrate (CH) and diazepam (DZ). When administered in vivo both drugs increase hyperploidy in male but not in female germ cells. In the assay presented here we show that both CH and DZ caused meiotic delay in in vitro maturing mouse oocytes. CH blocked meiotic progression irreversibly, affecting even dictyate stage oocytes. DZ-exposure slowed down maturation but many oocytes may eventually develop to metaphase II. Under the influence of CH asymmetric spindles were formed. Often chromosomes failed to align properly. This appeared to be responsible for triggering a meiotic checkpoint which arrests oocytes in meiosis I. Many oocytes escaping the block became 'diploid'. Lagging of chromosomes at anaphase I may contribute to significant rises in hypoploidy, while the scattering of chromosomes at metaphase II and the premature decondensation of chromatin may also predispose oocytes to the formation of structural and numerical chromosomal aberrations during meiosis II. In contrast, diazepam appeared to enhance the resumption of meiosis in immature oocytes at pharmacologically relevant doses, and only at high concentrations lead to a prominent meiotic arrest/delay. Importantly, several oocytes matured for 16 h in 25 micrograms/ml DZ displayed scattered chromosomes on the spindle and were hyperploid. Concomitantly, precocious separation of homologues occurred after DZ, and oocytes contained uneven numbers of chromatids, suggesting equational division at anaphase I. Cytoplasmic maturation. e.g., association of mitochondria with the spindle was disturbed by DZ. We compared the potential of the in vitro test to evaluate the aneugenic potential, the targets, threshold concentrations and long-lasting effects of relevant environmental pollutants on mammalian oogenesis with the in vivo findings, and evaluated the basis for sex-specific responses to aneugens.

Age Factors↗
PubMed1996

Disparate locations of the 52- and 60-kDa Ro/SS-A antigens in cultured human keratinocytes.

Anti-52- and anti-60-kDa Ro/SS-A (Ro) autoantibodies are produced by most patients with subacute cutaneous lupus erythematosus and neonatal lupus erythematosus and are thought to be pathogenic in these two disorders. To learn more about the epidermal antigens targeted by Ro autoantibodies, a panel of anti-52 and anti-60-kDa Ro antibodies was purified from human autoimmune sera and rabbit antisera and then used to: (i) determine the expression and location of the Ro antigens in human keratinocytes; (ii) clarify discrepancies in previous localization studies; and (iii) verify the existence of Ro autoantibodies that cross-react with the 52- and 60-kDa Ro antigens, as previously reported. By immunoblot analysis these antibodies demonstrate that 52- and 60-kDa Ro proteins are expressed in normal human skin and cultured keratinocytes. By indirect immunofluorescence studies with cultured human cells, the anti-52-kDa Ro antibodies produce fine granular cytoplasmic fluorescence and less intense nuclear fluorescence, with apparent nucleolar sparing. The anti-60-kDa Ro autoantibodies produce weak cytoplasmic fluorescence and intense coarse granular nuclear fluorescence with apparent nucleolar sparing. We found distinct differences in the intracellular localization of the 52- and 60-kDa Ro autoantigens. This difference suggests that the 52-and 60-kDa Ro antigens may have independent cellular functions. Finding 60-kDa Ro antigen predominantly in the nucleus challenges the notion that the majority of the intracellular 60-kDa Ro antigen is complexed with the cytoplasmic hY RNA. Additionally, our failure to find a cross-reactive epitope on these two proteins indicates that the 52-kDa Ro antigen is probably a true immunogen and not merely a protein that cross-reacts with anti-60-kDa Ro autoantibodies, as others have suggested.

Animals↗
PubMed1996

Effects of azimilide dihydrochloride on circus movement atrial flutter in the canine sterile pericarditis model.

INTRODUCTION: The effects of a Class III agent, azimilide dihydrochloride, on atrial flutter circuits were studies in a functional model of single loop reentrant atrial flutter using dogs, 3 to 5 days after production of sterile pericarditis. METHODS AND RESULTS: A computerized mapping system was used to construct activation maps from 138 to 222 epicardial sites in the right atrium. Doses of 3, 10, and 30 mg/kg i.v. azimilide dihydrochloride were analyzed in 8 dogs in which sustained atrial flutter lasting more than 30 minutes was induced by burst pacing. Atrial flutter was always due to single loop circus movement reentry in the lower right atrium. At 3 mg/kg, azimilide dihydrochloride terminated atrial flutter in 2 dogs; however, atrial flutter was reinduced. At 10 mg/kg, atrial flutter was terminated in all 8 dogs but was reinduced in 4 dogs with slower rate. At 30 mg/kg, atrial flutter was terminated in the remaining 4 dogs and could not be reinduced. Atrial flutter cycle length always increased prior to termination. Isochronal activation maps showed that the increase in cycle length was due to additional conduction delays in the slow zone of the reentrant circuit. The site of termination was always located within the slow conduction zone situated in the lower right atrium between the line of functional conduction block and the AV ring. Effective refractory periods (ERPs) were measured at selected sites in the slow zone and normal zone at twice diastolic threshold for the 10 mg/kg dose. Azimilide preferentially prolonged ERP in the slow zone (42.4 +/- 20.1 msec, mean +/- SD) compared with the normal zone (23.3 +/- 15.4 msec, P < 0.0001). The increase in cycle length corresponded with the increase in ERP in the slow zone. CONCLUSIONS: In a functional model of circus movement atrial flutter, azimilide dihydrochloride terminates and prevents reinduction of atrial flutter by a preferential increase in refractoriness leading to further conduction delay and conduction block in the slow zone of the functional reentrant circuit.

Animals↗
PubMed1996

The electrophysiological mechanism of ventricular arrhythmias in the long QT syndrome. Tridimensional mapping of activation and recovery patterns.

We have previously developed a canine in vivo model of the long QT syndrome (LQTS) using the neurotoxin anthopleurin A (AP-A), which acts by slowing sodium channel inactivation. The recent discovery of a genetic mutation in the cardiac sodium channel in some patients with the congenital LQTS, resulting in abnormal gating behavior similar to sodium channels exposed to AP-A, provides a strong endorsement of this animal model as a valid surrogate to the clinical syndrome of LQTS. In the present study, we conducted high-resolution tridimensional isochronal mapping of both activation and repolarization patterns in puppies exposed to AP-A that developed LQTS and polymorphic ventricular tachyarrhythmias (VTs). To map repolarization, we measured activation-recovery intervals (ARIs) using multiple unipolar extracellular electrograms. We demonstrated, for the first time in vivo, the existence of spatial dispersion of repolarization in the ventricular wall and differences in regional recovery in response to cycle-length changes that were markedly exaggerated after AP-A administration. Analysis of tridimensional activation patterns showed that the initial beat of polymorphic VT consistently arose as focal activity from a subendocardial site, whereas subsequent beats were due to successive subendocardial focal activity, reentrant excitation, or a combination of both mechanisms. Reentrant excitation was due to infringement of a focal activity on the spatial dispersion of repolarization, resulting in functional conduction block and circulating wave fronts. The polymorphic QRS configuration of VT in the LQTS was due to either changing the site of origin of focal activity, resulting in varying activation patterns, or varying orientations of circulating wave fronts.

Animals↗