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Biomedical subjects

J W Moore

Publications and source records attributed to J W Moore.

At least 307 records · Page 17Linked to original sources
PubMed1966

Blockage of sodium conductance increase in lobster giant axon by tarichatoxin (tetrodotoxin).

Tarichatoxin, isolated from California newt eggs, has been found to selectively block the increase of sodium conductance associated with excitation in lobster giant axons at nanomolar concentrations. This resulted from a reduction in the amplitude of the conductance increase rather than a change in its temporal characteristics. The normal potassium conductance increase with depolarization is not altered. A high concentration of calcium applied concomitantly with the toxin significantly improves the reversibility of the sodium blocking. This toxin has recently been identified as chemically identical with tetrodotoxin from the puffer fish. Toxins from the two sources are equally effective and are shown to have an action which is distinctly different from that of procaine.

Animals↗
PubMed1966

Ionic conductance changes in lobster axon membrane when lanthanum is substituted for calcium.

The trivalent rare earth lanthanum was substituted for calcium in the sea water bathing the exterior of an "artificial node" of a lobster axon in a sucrose gap. It caused a progressive rise in threshold, and a decrease in the height of the action potential as well as in its rates of rise and fall. Prolonged application produced an excitation block. Voltage-clamp studies of the ionic currents showed that the time courses of the ionic conductance changes for both sodium and potassium were increased. Concurrently, the potentials at which the conductance increases occurred were shifted to more positive inside values for the La+++ sea water. These effects resemble changes resulting from a high external calcium concentration. Over and above this, La+++ also causes a marked reduction in the maximum amount of conductance increase following a depolarizing potential step. Membrane action potentials similar to those observed experimentally in the La+++ solution have been computed with appropriate parameter changes in the Hodgkin-Huxley equations.

Action Potentials↗
PubMedDate not supplied

Truncus arteriosus associated with trisomy 18.

The spectrum of cardiac anomalies in trisomy 18 typically includes septal defects and polyvalvular disease and only rarely complex malformations. We report the first case of trisomy 18 with truncus arteriosus type II.

Chromosome Aberrations↗
PubMedDate not supplied

Tolerance of normal aorta to oversized dual balloon valvuloplasty. Observations in a swine model: technical note.

The damage threshold during aortic valvuloplasty was determined in 12 normal swine subjected to inflation of oversized dual balloons. Catheters with combined balloon diameters of 1.2-2.0 times the aortic annulus were selected. Following completion of the procedure, the animals were sacrificed and examined for pathology. With combined balloon diameters less than or equal to 1.7 times the aortic annulus, there was no gross or microscopic damage. In animals with combined diameters equal to 2 times the aortic annulus, there was rupture of the aorta. This data provides further basis for the selection of catheter sizes in dual balloon aortic valvuloplasty.

Angioplasty, Balloon↗
PubMedDate not supplied

Use of an intravascular endoprosthesis (stent) to establish and maintain short-term patency of the ductus arteriosus in newborn lambs.

The feasibility of stenting the ductus arteriosus with a balloon-expandable vascular endoprosthesis was tested in 8 newborn lambs. Tantalum wire and stainless steel mesh coronary stents were implanted antegrade or retrograde by percutaneous transfemoral catheterization. One lamb died during the procedure from perforation of the aorta. In 7 lambs, the ductus arteriosus was crossed using endhole catheters and wires, and stents mounted on angioplasty catheters were expanded in the ductus arteriosus. Six lambs had successful implantation and had maintained a sizeable patent ductus arteriosus at 2 h. We conclude that the feasibility of percutaneous stenting of the newborn ductus was demonstrated. By providing patency of the ductus arteriosus, stents may offer nonsurgical alternatives for palliation of cyanotic congenital heart disease and hypoplastic left heart syndrome.

Animals↗
PubMedDate not supplied

Afterload reduction therapy in patients following intraatrial baffle operation for transposition of the great arteries.

Patients with intraatrial baffle procedure for transposition of the great arteries (TGA) have diastolic dysfunction, decreased exercise capacity, stroke volume response and elevated systemic vascular resistance (SVR) during exercise. Angiotensin-converting enzyme (ACE) inhibitors improve exercise capacity in adults with congestive heart failure by improving diastolic function and decreasing SVR. We tested the hypothesis that ACE inhibitors decrease SVR and improve exercise capacity in patients after intraatrial baffle procedure for TGA. We studied the effects of enalapril in nine patients with TGA s/p intraatrial switch (mean age, 13.8 +/- 3 years) 7 to 21 years (mean, 12 +/- 4 years) after intraatrial baffle procedure. Enalapril (0.5 mg/kg/day, maximum dosage 20 mg bid) was administered for 12 months. Patients exercised using a cycle ergometer ramp protocol (0.25 W/kg/min) before enalapril (baseline), 1 month, 6 months, and 12 months after treatment initiation. Heart rate, blood pressure, cardiac output, respiratory rate, minute ventilation, oxygen consumption (VO2), total exercise time, work, and power were measured. SVR, cardiac index, and stroke volume index (SVI) were calculated. Two-tailed paired Student's t-test was used to compare data to those of normal control patients and the patients' baseline data. Patients had lower resting heart rate, cardiac index, maximum heart rate, cardiac index (CI), SVI, VO2, exercise time, work, and power and higher maximal SVR at baseline compared to normal control patients. There was no significant difference in total exercise time, work, power, VO2 (rest/peak), SVR, SVI, and CI after 12 months of therapy compared to patients' baseline values. We conclude that short-term (<1 year) use of enalapril does not improve exercise performance in patients with TGA in whom the intraatrial baffle procedure has been performed.

Adolescent↗
PubMedDate not supplied

Embolization and transcatheter retrieval of coils and devices.

Embolizations of coils and devices are well-known complications of transcatheter procedures performed in order to occlude extracardiac or intracardiac shunts. A review of the literature and of our experience was performed to provide a succinct review of existing transcatheter retrieval techniques. After embolization of a coil or device, the appropriate initial procedure involves repositioning of the coil or device using a snare or bioptome to a location where harm to the patient is minimized. The subsequent retrieval technique depends on the characteristics of the coil or device involved. Coils may be retrieved using a bioptome or a snare. Devices must be snared, often in specific places. Both may be pulled into long or short, appropriately sized retrieval sheaths. To minimize potential morbidities associated with these retrievals and to maximize efficacy of retrieval, operators performing transcatheter coil or device occlusions must be familiar with retrieval techniques.

Cardiac Catheterization↗
PubMedDate not supplied

Conditioned response timing and integration in the cerebellum.

Classical conditioning procedures instill knowledge about the temporal relationships between events. The unconditioned stimulus (US) is the event to be timed. The conditioned response (CR) is viewed as a prediction of the imminence of the US. Knowledge of the elapsed time between conditioned stimuli (CSs) and US delivery is expressed in the topological features of the CR. The peak amplitude of the CR coincides with the timing of the US. A simple connectionist network based on Sutton and Barto's Time Derivative (TD) Model of Pavlovian Reinforcement provides a mechanism that can account for and simulate CR timing in a variety of protocols. This article describes extensions of the model to predictive timing under temporal uncertainty. The model is expressed in terms of equations that operate in real time according to a competitive learning rule. The unfolding of time from the onsets and offsets of events such as CSs is represented by the propagation of activity along a sequence of time-tagged elements. The model can be aligned with anatomical circuits of the cerebellum and brain stem that are essential for learning and performance of conditioned eye-blink responses.

Animals↗
PubMedDate not supplied

Secundum-type atrial septal defects with failure to thrive in the first year of life.

This article summarizes the case histories of six infants who had isolated secundum-type atrial septal defects (ASDs) and presented with failure to thrive in the first year of life. Patients underwent operative closure of their ASD with the expectation that this would improve their feeding and growth pattern. Five of the six children demonstrated little or no improvement in symptoms following operation. Each of these five patients have subsequently shown signs of developmental delay. Our experience with this group suggests that failure to thrive associated with a secundum ASD will frequently have a noncardiac basis.

Child Development↗
PubMedDate not supplied

Bone scan: indium-WBC correlation in the diagnosis of osteomyelitis of the foot.

A retrospective study was performed of 20 podiatric cases using technetium-99m methylene diphosphonate three-phase bone scans along with indium-111 oxine leukocyte scans, as needed, to determine the presence and extent of osteomyelitis of the foot. Using criteria developed at our institution, the authors attempt to provide a mechanism to make a reliable diagnosis for osteomyelitis that has been supported by surgical/pathologic confirmation of long-term clinical follow-up. The sensitivity, using bone scans alone, was 100%, and specificity was 47%. Correlating bone and indium-111 leukocyte scans yielded a sensitivity of 100% with a specificity raised to 81%. Indium-111 leukocyte scans were used in 40% of cases when a definitive diagnosis for osteomyelitis could not be made on the basis of the three-phase bone scan or clinical presentation alone. Indium-111 leukocyte scans were also helpful in delineating the extent of the disease process. The authors present a standard technique for a 5-hour delayed imaging in the three-phase bone scan, as well as marking the foot in the indium-111 leukocyte scan with three routine views obtained for each imaging procedure, to ensure clinical accuracy.

Adult↗