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Biomedical subjects

J P Li

Publications and source records attributed to J P Li.

At least 19 recordsLinked to original sources
PubMed1992

Successful sequential radiofrequency catheter ablation of anatomically discrete antegrade and retrograde accessory pathway conduction in the Wolff-Parkinson-White syndrome.

Histopathologically, accessory atrioventricular (AV) pathways comprise tiny strands of working myocardium that traverse the AV groove and link between the atrial and ventricular myocardium. Antegrade and retrograde conduction in bidirectional accessory pathways have generally been considered to occur along the same fibers. This report details the successful catheter ablation of a left free wall accessory pathway with radiofrequency energy. Antegrade and retrograde conduction of the pathway were abolished sequentially by separate episodes of energy delivered at anatomically discrete though closely adjacent sites along the mitral annulus. This finding raises the interesting possibility of anatomic "compartmentalization" of antegrade and retrograde conduction along an accessory pathway.

Adult↗
PubMed1992

Identification of insecticidal peptides from venom of the trap-door spider, Aptostichus schlingeri (Ctenizidae).

Nine insecticidal peptides were isolated from the venom of the trap-door spider, Aptostichus schlingeri. Seven of these toxins cause flaccid paralysis of insect larvae within 10 min of injection and all were lethal within 24 hr. The complete amino acid sequences (32-76 residues) of six peptides are presented. The identified peptides contain three or four disulfide bonds and the larger peptides (74-76 residues) are quite similar in sequence with carboxyl termini as free acids, not amidated.

Amino Acid Sequence↗
PubMed1992

Ventricular rate-adaptive pacing in the elderly.

The role of ventricular rate-adaptive pacing (VVIR) in the elderly was investigated in 12 patients with a mean age of 85 +/- 2 years (range 75-95 years) with implanted activity-initiated VVIR pacemakers. Although four patients had significant extracardiac diseases, all were capable of independent walking and self care. The pacing rate achieved during structured daily activities (walking, climbing stairs, washing, bed-making and scrubbing floors) were compared with those achieved by 10 age-matched healthy subjects. Apart from the more strenuous activities (ascending stairs and floor-scrubbing), the pacing rates achieved by the patients were comparable to those of the healthy subjects and occurred within an appropriate time. In a 4-weekly randomized, double-blind crossover protocol in the VVI and VVIR pacing modes, all patients underwent assessments in a 12-min walking distance test, a 24 h non-invasive ambulatory blood pressure recording and a symptomatic documentation. During VVIR pacing, the 12-min walking distance was significantly improved compared to VVI pacing (556 +/- 52 vs. 545 +/- 55 m, P less than 0.05). There was no difference between the recorded blood pressure and symptom scores between the two pacing modes, although most patients preferred VVIR pacing (P less than 0.05). It is concluded that VVIR pacing in this elderly population can improve exercise capacity, and the patients' preference for the VVIR mode was documented despite the absence of a measurable difference in symptomatology.

Aged↗
PubMed1992

Complete structure of eclosion hormone of Manduca sexta. Assignment of disulfide bond location.

The locations of the three disulfide bonds of eclosion hormone (EH) isolated from Manduca sexta were assigned by sequence analysis of thermolysin fragments and by comparison of a key heterodimeric fragment to regiospecifically synthesized parallel and antiparallel isomers. We elucidated the complete structure of Manduca EH as a 62-residue peptide which has three disulfide bonds between Cys14-Cys38, Cys18-Cys34, and Cys21-Cys49.

Amino Acid Sequence↗
PubMed1992

The use of implantable sensors for the control of pacemaker mediated tachycardias: a comparative evaluation between minute ventilation sensing and acceleration sensing dual chamber rate adaptive pacemakers.

The role of implantable sensors to control pacemaker mediated tachycardias was investigated in 16 patients with two different dual chamber rate adaptive (DDDR) pacemakers, which sensed eiter minute ventilation (DDDR-Meta, nine patients) or body acceleration (Relay, seven patients). Successive atrial sensed events beyond a programmable rate occurring in the absence of detection of exercise by the sensors were considered to represent retrograde conduction or atrial arrhythmias, and the pacemakers responded by either a mode shift from DDDR to ventricular rate adaptive (VVIR) pacing (DDDR-Meta) or by tracking at an interim rate, the so-called conditional ventricular tracking limit (CVTL, Relay). In the unipolar atrial sensing mode, myopotential sensing (MPI) and external chest wall stimulations (CWS) at 250 beats/min were induced to be preferentially sensed by the atrial channel to simulate the conditions of atrial arrhythmias. In the DDD mode, these maneuvers resulted in ventricular responses of 88 +/- 3 beats/min and 110 +/- 3 beats/min for MPI and CWS, respectively. The pacing rate was significantly reduced in the DDDR mode with the sensors correctly detecting and responding to the sensed abnormal atrial signals (68 +/- 5 beats/min during MPI and 71 +/- 5 beats/min during CWS, P less than 0.005 compared with the corresponding DDD rate). One patient with a Relay pacemaker developed spontaneous atrial flutter and the ventricular tracking responses were 140 and 85 beats/min in the DDD and DDDR pacing modes, respectively. Thus MPI and CWS are useful bedside testing methods to assess pacemaker response during atrial arrhythmias. The use of implantable sensors to judge the appropriateness of atrial rate is a new approach to the management of pacemaker mediated tachycardias.

Adult↗
PubMed1992

Atrial arrhythmia management with sensor controlled atrial refractory period and automatic mode switching in patients with minute ventilation sensing dual chamber rate adaptive pacemakers.

Although a long postventricular atrial refractory period (PVARP) may prevent the occurrence of pacemaker mediated tachycardias and inadvertent tracking of atrial arrhythmias in dual chamber (DDD) pacing, the maximum upper rate will necessarily be compromised. We tested the feasibility of using minute ventilation sensing in a dual chamber rate adaptive pacemaker (DDDR) to shorten the PVARP during exercise in 13 patients with bradycardias (resting PVARP = 463 +/- 29 msec) to avoid premature upper rate behavior. Graded treadmill exercise tests in the DDD and DDDR modes at this PVARP resulted in maximum ventricular rates of 98 +/- 8 and 142 +/- 3 beats/min, respectively (P < 0.0001), due to chronotropic incompetence and upper rate limitation in the DDD mode, both circumvened with the use of sensor. In order to stimulate atrial arrhythmias, chest wall stimulation was applied for 30 seconds at a rate of 250 beats/min at a mean unipolar atrial sensitivity of 0.82 mV. Irregular ventricular responses occurred in the DDD mode (the rates at a PVARP of 280 and 463 +/- 29 msec were, respectively 92 +/- 5 and 66 +/- 3 msec; P < 0.0001). In the DDDR mode at a PVARP of 463 +/- 29 msec, regular ventricular pacing at 53 +/- 2 beats/min occurred due to mode switching to VVIR mode in the presence of repetitive sensed atrial events within the PVARP. One patient developed spontaneous atrial fibrillation on follow-up, which was correctly identified by the pacemaker algorithm, resulting in mode switch from DDDR to regular VVIR pacing and preservation of rate response. In conclusion, sensor controlled PVARP allows a long PVARP to be used at rest without limiting the maximum rate during exercise. In addition, to offer protection against retrograde conduction, a long PVARP and mode switching also limit the rate during atrial arrhythmias and allow regular ventricular rate responses according to the physiological demands.

Aged↗
PubMed1992

Initial clinical experience with a single pass VDDR pacing system.

Although ventricular rate adaptive pacing (VVIR) improves exercise capacity and cardiac output compared to constant rate ventricular pacing (VVI), this pacing mode does not provide benefit of atrioventricular (AV) synchrony. We evaluated the use of a custom-built VDDR pacing system using a single pass, ventricular lead, which detects endocavity P wave using a pair of diagonally arranged atrial bipolar (DAB) electrodes. In the VDDR mode, AV synchrony is enabled and the P wave rate is used in conjunction with an accelerometer based activity sensor for rate adaptive pacing. A VDDR pacemaker was implanted in three patients with complete AV block (mean age 63 +/- 1 year) and the mean implantation time was 29 minutes. Mean P wave amplitude was 2.4 mV (1.2-4.2 mV) at implantation and telemetered P wave amplitude was stable over a follow-up of 6 months. At a sensitivity of 0.2 mV, stable P wave sensing was observed during breathing maneuvers, arm swinging, myopotential induction, and Holter recording. Paired exercise tests performed in the VDDR and VVIR modes showed higher cardiac output at rest, during exercise, and in the recovery period in the VDDR pacing mode. Thus VDDR pacing using a single pass lead is superior to VVIR pacing by enabling P synchronous ventricular pacing without adding to the complexity of implantation.

Acceleration↗
PubMed1992

Clinical experience with an activity sensing DDDR pacemaker using an accelerometer sensor.

The rate adaptive characteristics and pacemaker mediated tachycardia protection algorithm of an accelerometer based DDDR pacemaker were evaluated in 11 patients with bradycardia (seven atrioventricular block, four sick sinus syndrome). Rate adaptive programming was effected by collecting the acceleration level during a 3-minute moderate exercise ("tailoring" of sensor). In comparison with an externally attached piezoelectric sensor, the accelerometer sensor showed lower rate changes during external tapping of the pacemaker (16 +/- 3 vs 29 +/- 4 ppm, P less than 0.02) and applied direct pressure (1 +/- 1 vs 40 +/- 3 beats/min, P less than 0.001) on the pacemaker. At nominal setting, the accelerometer sensor showed improved rate stability and higher rate response to jogging and standing, although responses to other daily activities and treadmill exercise were similar. Apart from changing the rate responsive slope, rate response could be improved by repeat "tailoring" of the sensor at a lower exercise level, resulting in better overall rate response characteristics. The ability of the rate monitoring software to collect acceleration levels for an activity and profile the projected rate response at different rate responsive settings allowed programming to be effected with the minimum amount of exercise testing. The pacemaker also discriminated atrial tachyarrhythmias from normal sinus response using the sensor to judge the appropriateness of the atrial rate, which correctly identified and prevented rapid ventricular tracking in two patients during atrial flutter/fibrillation.

Adult↗
PubMed1992

Bidirectional tachycardia induced by herbal aconite poisoning.

This report details the clinical, electrocardiographic, and electropharmacological characteristics of an unusual case of bidirectional tachycardia induced by aconites present in a Chinese herbal decoction consumed by a previously healthy subject. The tachycardia showed marked susceptibility to vagotonic maneuvers, cholinesterase inhibition, and adenosine triphosphate. The incessant nature of the tachycardia, rapid recurrence after transient suppression, and failure to respond to direct current cardioversion suggested an automatic tachycardia mechanism consistent with known data on the cellular electrophysiological mechanism of aconitine-mediated arrhythmogenesis. A fascicular or ventricular myocardial origin of the tachycardia with alternating activation patterns, or dual foci with alternate discharge, appeared most plausible. The rootstocks of aconitum plants have been commonly employed in traditional Chinese herbal recipes for "cardiotonic" actions and for relieving "rheumatism." Multiple pitfalls could occur during the processing of these herbs that might have predisposed to aconite poisoning. The need for strict control and surveillance of herbal substances with low margins of safety is highlighted.

Aconitum↗
PubMed1992

Incessant automatic ventricular tachycardia complicating acute coxsackie B myocarditis.

A 13-year-old girl presented with incessant ventricular tachycardia complicating acute Coxsackie B3 myocarditis. Electrophysiologic assessment revealed that the tachycardia could not be terminated, overdrive suppressed or accelerated by programmed electrical stimulation, but was transiently slowed by intravenous adenosine triphosphate and had marked spontaneous and sympathoautonomic-mediated fluctuation in the tachycardia cycle length. These features were atypical of reentry and triggered automaticity and suggested that abnormal automaticity was the likely tachycardia mechanism. Intravenous amiodarone slowed the ventricular tachycardia, but the patient eventually succumbed from rapidly progressive left ventricular failure. Postmortem pathohistologic examination confirmed the diagnosis of acute myocarditis.

Adolescent↗
PubMed1992

[Evaluation of cellular immunity in pulmonary sarcoidosis and primary lung cancer].

We tested the cellular immunity of the patients with pulmonary sarcoidosis (n = 16) and primary lung cancer (n = 14). The data showed that PHA-p induced peripheral blood lymphocyte (PBL) proliferation and interleukin 2 (IL-2) productivity were significantly reduced in both patients groups, and also the PBL proliferation induced by exogenous recombined IL-2 was reduced, but not significantly (P > 0.05) compared with normal central. Our results suggested that cellular immunodepression may exist in pulmonary sarcoidosis and primary lung cancer patients, the exogenous IL-2 can partly restore the reduced PBL proliferation. So the cytokine may play a role in the immunologic treatment of lung cancer and the research of pulmonary sarcoidosis.

Adult↗
PubMed1991

Identification of an allatostatin from the tobacco hornworm Manduca sexta.

A peptide (Manduca sexta allatostatin) that strongly inhibits juvenile hormone biosynthesis in vitro by the corpora allata from fifth-stadium larvae and adult females has been purified from extracts of heads of pharate adult M. sexta by a nine-step purification procedure. The primary structure of this 15-residue peptide has been determined: pGlu-Val-Arg-Phe-Arg-Gln-Cys- Tyr-Phe-Asn-Pro-Ile-Ser-Cys-Phe-OH, where pGlu is pyroglutamate). To our knowledge, this neuro-hormone has no sequence similarity with any known neuropeptide from other organisms. The synthetic free acid and amide forms showed in vitro activity indistinguishable from that of native M. sexta allatostatin. The ED50 of synthetic M. sexta allatostatin on early fifth stadium larval corpora allata in vitro was approximately 2 nM. This inhibition was reversible. In a cross-species study, M. sexta allatostatin also inhibited the corpora allata of adult female Heliothis virescens but had no effect on the activity of corpora allata of adult females of the beetle Tenebrio molitor, the grasshopper Melanoplus sanguinipes, or the cockroach Periplaneta americana.

Amino Acid Sequence↗
PubMed1991

Isolation and identification of paralytic peptides from hemolymph of the lepidopteran insects Manduca sexta, Spodoptera exigua, and Heliothis virescens.

Seven paralytic peptides were isolated and identified from lepidopteran hemolymph. All of these peptides cause rapid, rigid paralysis when injected into Manduca sexta and some other lepidopteran larvae. Each peptide contains 23 amino acid residues including 2 cysteines and the carboxyl termini are acidic. Synthetic peptides in the disulfide or reduced forms, and as carboxyl-terminal acids or amides were equally paralytic. The most potent paralytic peptide, Mas PP I, has the following sequence: H-Glu-Asn-Phe-Ala-Gly-Gly-Cys-Ala-Thr-Gly-Tyr-Leu- Arg-Thr-Ala-Asp-Gly-Arg-Cys-Lys-Pro-Thr-Phe-OH. The two peptides from M. sexta hemolymph are remarkable in that they are autoparalytic (i.e. factors in collected hemolymph that are paralytic when injected into the same larvae).

Amino Acid Sequence↗
PubMed1991

Purification and immunogenicity of genetically obtained pneumolysin toxoids and their conjugation to Streptococcus pneumoniae type 19F polysaccharide.

As part of an ongoing study concerned with improving human vaccines against Streptococcus pneumoniae, the genes for two defined pneumolysin (PL) toxoids (pneumolysoids), Pd-A (PL with a Cys----Gly substitution at amino acid 428) and Pd-B (PL with a Trp----Phe substitution at position 433), were inserted into the high-expression vector pKK233-2 in Escherichia coli and the pneumolysoids were purified. Groups of mice which had been immunized with either Pd-A, Pd-B, or native PL purified from S. pneumoniae were then challenged either intranasally or intraperitoneally with virulent pneumococci. Mice in all immunized groups survived significantly longer than sham-immunized controls. Both pneumolysoids were more effective than PL as protective immunogens. Pneumolysoid Pd-B was conjugated covalently with pneumococcal type 19F capsular polysaccharide (19F PS), and the immunogenicities of both the protein and the PS moieties of the conjugate in mice were determined. Significant anti-PL titers were obtained, and the immunogenicity of the 19F PS moiety was markedly enhanced compared with that of unconjugated PS. Conjugation also appears to have converted the 19F PS into an antigen capable of inducing a booster effect. These results support the notion that the efficacy of human, PS-based antipneumococcal vaccines might be improved by supplementation with pneumolysoid in the form of a covalent pneumolysoid-PS conjugate.

Amino Acid Sequence↗
PubMed1991

Mechanism of leukemogenesis induced by mink cell focus-forming murine leukemia viruses.

The Friend or Moloney mink cell focus-forming (MCF) virus encodes a recombinant-type envelope glycoprotein, gp70, that is closely related to the membrane glycoprotein, gp55, of Friend spleen focus-forming virus (SFFV). We have shown previously that gp55 has the ability to activate cell growth by binding to the cellular receptor for erythropoietin. Here we show that gp70 encoded by either the Friend or Moloney MCF virus also binds to the erythropoietin receptor and that coexpression of the receptor and gp70 in an interleukin-3 (IL-3)-dependent cell line can activate IL-3-independent growth. Furthermore, when the cDNA for the human IL-2 receptor beta chain, which is related by sequence to the erythropoietin receptor, was introduced into this cell line, it became growth factor independent after infection either with SFFV or with one of the two MCF viruses but not with an ecotropic virus. Based on these observations, we propose a mechanism for the early stage of leukemogenesis induced by the MCF-type murine leukemia viruses.

Animals↗
PubMed1991

Virulence, immunity, and vaccine related to Streptococcus pneumoniae.

The pathogenesis of bacterial infection involves a series of interactions between the virulence determinants of the microorganisms and the immunity of the host. Studies on the molecular structure and immunological properties of pneumococcal virulence factors have provided general knowledge for the chemical basis of immunogenicity and prevention of bacterial infection. Antibody responses to PS and protein antigens can be greatly affected by their physicochemical properties, e.g., molecular size, specific determinants, conformation, etc. Characterization of group 19 pneumolysins and cloning of their ply genes were studied to examine the relationship of ply to virulence. Group 19 pneumococci all contained ply; the disease-isolated types of 19F and 19A appeared to show a higher specific hemolytic activity and yield than the nonpathogenic types, 19B and 19C. Genomic DNA that contained the ply gene from group 19 strains were analyzed by the polymerase chain reaction (PCR). Type 2 oligonucleotide primers recognized and initiated synthesis of an identical 1.5 kb DNA fragment in types 2, 19F, 19A, 19B, and 19C. Their sizes of restriction DNA fragments were also found to be homologous. Thus, group 19 ply genes showed remarkably similar characteristics. A difficult problem in the development of vaccines against bacterial diseases is the poor immune response of young children to purified PSs. The efficacy of pneumococcal vaccine might be improved by supplementation with inactivated pneumolysin in the form of a PS-protein conjugate.

Animals↗