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Biomedical subjects

M L Epstein

Publications and source records attributed to M L Epstein.

At least 73 records · Page 4Linked to original sources
PubMed1982

Enhanced atrioventricular conduction in patients without preexcitation syndrome: relation to heart rate in paroxysmal reciprocating tachycardia.

We studied the electrophysiologic characteristics of atrioventricular (AV) nodal conduction in patients with reciprocating tachycardia (RT) without ventricular preexcitation, and the relation of these characteristics to RT cycle length (CL). Thirty-five symptomatic patients who had a normal PR interval (0.13-0.20 second) during sinus rhythm underwent detailed intracardiac electrophysiologic study during which ventricular preexcitation was excluded, and the RT mechanism was determined. RT was due to reentry using an accessory AV pathway capable of conduction only in the retrograde direction (concealed AP) in 13 patients (37%) and to reentry within the AV node in 22 (63%). Dynamic properties of AV conduction (assessed by degree of AH prolongation during progressive increase in atrial pacing rate) were normally distributed (p less then 0.005); 12 patients (34%) fulfilled the criteria for enhanced AV conduction (EAVC). The patients with EAVC had a shorter RT CL than did patients without EAVC (294 +/- 43.3 msec vs 360 +/- 68.1 msec, p less than 0.01). However, CL differences were primarily due to the influence of EAVC in the subgroup of patients with RT using a concealed AP (EAVC CL, 274 +/- 35.1 msec; without EAVC, 326 +/- 15.7 msec, p less than 0.005). The RT CL in patients with reentry within AV node was not measureable influenced by concomitant EAVC (EAVC, 314 +/- 43.8 msec; without EAVC, 376 +/- 76.8 msec) (NS). This study suggests that despite the presence of a normal PR interval during sinus rhythm, dynamic AV conduction responses can vary widely in patients with RT. In patients with RT using a concealed AP, but not in those with reentry within the AV node, coexisting diminished physiologic AV conduction slowing may be associated with more rapid tachycardia rates.

Adult↗
PubMed1981

Long-term evaluation of persistent supraventricular tachycardia in children: clinical and electrocardiographic features.

Although the long-term prognosis of children with persistent supraventricular tachycardia (SVT) has been generally considered benign, recent reports have suggested that some of these patients may develop cardiac dysfunction secondary to their persistent SVT. The clinical course of six children demonstrating ECG criteria of persistent SVT are presented herein with follow-up data for 5 to 20 years. Persistent SVT was present in each patient from 2 to 19 years. Two patients had transient congestive heart failure early in their course of persistent SVT, and two others demonstrated continued roentgenographic evidence of mild cardiomegaly without associated symptomatology. Conventional antiarrhythmics administered briefly in five patients and chronically in two were without effect on their arrhythmias. Persistent SVT remains in three patients and a fourth continues to exhibit intermittent episodes of SVT; however, all six patients are currently asymptomatic with two in stable normal sinus rhythm. This investigation indicates that the persistent form of SVT (lasting more than 1 year) is uncommon among children with paroxysmal SVT, and long-term observation of the consequences of persistent SVT supports the view that this rhythm disturbance is generally well tolerated in such patients.

Adolescent↗
PubMed1981

Development of enkephalinergic neurons in the gut of the chick.

The content and distribution of Met-enkephalin immunoreactivity in the developing chick gut was studied by radioimmunoassay and immunocytochemistry. Met-enkephalin was detected by radioimmunoassay in the duodenum of the 5-day chick embryo. The concentration in this region increased 4-fold by 13 days of incubation and declined thereafter to the levels found in the 4-week chicken. The concentration of enkephalin in the midgut increased about 2-fold between 9 and 13 days of incubation and remained constant until hatching. In the 7-day duodenum, metenkephalin immunoreactivity was found in a network of darkly stained nodes (accumulations of ganglion cells) faintly stained internodal nerve bundles; this network of immunoreactivity was localized to the myenteric plexus. By 9 days of incubation, the network was more extensive and the intensity of staining was increased. At 13 days of incubation, varicosities were found in the region of the ganglion cells and in internodal nerve bundles. At this time, immunoreactivity was clearly visualized in the submucosal plexus. In the newly hatched chicken, met-enkephalin was found in nerves within the circular smooth muscle, as well as the myenteric and submucosal plexuses. The early appearance of met-enkephalin in the developing chick enteric nervous system suggests this peptide may act as a primary neurotransmitter in the organization and control of gut motility.

Animals↗
PubMed1980

Predictive value of the echocardiographic left atrial dimension in isolated ventricular septal defect.

Echocardiographic left atrial dimension has been reported to correlate with left-to-right shunt (Qp/Qs) in children with isolated ventricular septal defect (VSD) or patent ductus arteriosus (PDA). In 17 children with isolated VSD, we prospectively compared Qp/Qs with the ratio of echocardiographic left atrial dimension to aortic root diameter (LAD/Ao) and with the left atrial dimension corrected for body surface area (LAD/M2). The correlation between LAD/Ao and Qp/Qs was not statistically significant (r = 0.49, p > 0.05). The LAD/M2 correlated significantly with Qp/Qs (r = 0.66, p < 0.01); however, prediction intervals were excessively wide. Our findings indicate that it is inappropriate to predict Qp/Qs in these patients from echocardiographic LAD.

Adolescent↗
PubMed1980

Electrical activity in cardiac mutant axolotl hearts.

Electrical recordings from the hearts of both cardiac lethal mutant and normal embryos showed the presence of action potentials conducted over the heart tube. Ionic coupling and gap junctions also were observed in both. These results suggest that the absence of heart function in mutant embryos does not result from a defect in electrical activity.

Action Potentials↗
PubMed1979

Incessant atrial tachycardia in childhood: association with rate-dependent conduction in an accessory atrioventricular pathway.

A detailed electrophysiologic study in a 7 year old boy with incessant atrial tachycardia revealed the presence of an atrioventricular pathway conducting only in the ventriculoatrial direction. The results indicate a reentrant mechanism with the retrograde limb of the circuit entering the atrium in the region of the proximal to mid coronary sinus. The accessory pathway exhibited relatively long conduction times and conduction properties suggesting decremental conduction. Thus, an electrophysiologically atypical anomalous conduction pathway may be responsible for the occurrence of incessant atrial tachycardial in some children.

Atrioventricular Node↗
PubMed1979

Pulmonary artery banding in infants with complete atrioventricular canal.

Management of symptomatic atrioventricular canal (AVC) in infancy may be difficult. Between July, 1969, and September, 1977, 31 infants with complete AVC presented in congestive heart failure (CHF) to the University of Minnesota Hospitals. Fifteen of these patients have responded to medical management and have been followed as outpatients. The other 16 patients remained in CHF. Six of them died of persistent heart failure within 4 months. The other 10 infants, aged 3 weeks to 1 year (mean 4 months), underwent pulmonary artery banding and seven survived operation. One of the survivors died with apparent pneumonia 1 month postoperatively. Each of the remaining six patients, who have been followed for 9 months to 9 years, had minimal mitral insufficiency and a large ventricular shunt. The three patients dying after banding had significant mitral insufficiency. We believe that pulmonary artery banding is an effective palliative procedure for infants with complete AVC and CHF who have large ventricular shunts and minimal mitral insufficiency.

Angiocardiography↗
PubMed1978

Cell-to-cell communication and ovulation. A study of the cumulus-oocyte complex.

Cell-to-cell communication was characterized in cumulus-oocyte complexes from rat ovarian follicles before and after ovulation. Numerous, small gap junctional contacts were present between cumulus cells and oocytes before ovulation. The gap junction are formed on the oocyte surface by cumulus cell processes that transverse the zona pellucida and contact the oolemma. The entire cumulus mass was also connected by gap junctions via cumulus-cumulus interactions. In the hours preceding ovulation, the frequency of gap junctional contacts between cumulus cells and the oocyte was reduced, and the cumulus was disorganized. Electrophysiological measurements indicated that bidirectional ionic coupling was present between the cumulus and oocyte before ovulation. In addition, iontophoretically injected fluorescein dye was tranferred between the oocyte and cumulus cells. Examination of the extent of ionic coupling in cumulus-oocyte specimens before and after ovulation revealed that ionic coupling between the cumulus and oocyte progressively decreased as the time of ovulation approached. In postovulatory specimens, no coupling was detected. Although some proteolytic mechanism may be involved in the disintegration of the cumulus-oocyte complex, neither the cumulus cells nor the oocyte produced detectable levels of plasminogen activator, a protease which is synthesized by membrana granulosa cells. In summary, cell communication is a characterisitc feature of the cumulus-oocyte complex, and this communication is terminated near the time of ovulation. This temporal pattern of the termination of communication between the cumulus and the oocyte may indicate that communication provides a mechanism for regulating the maturation of the oocyte during follicular development before ovulation.

Animals↗
PubMed1977

A study of communication specificity between cells in culture.

We have examined the specificity of communication between cells in culture by co-culturing cells derived from mammalian, avian, and arthropod organisms. Both mammalian and avian culture cells have similar gap junctional phenotypes, while the insect (arthropod) cell lines have a significantly different gap junctional structure. Electrophysiological and ultrastructural methods were used to examine ionic coupling and junctional interactions between homologous and heterologous cell types. In homologous cell systems, gap junctions and ionic coupling are present at a high incidence. Also, heterologous vertebrate cells in co-culture can communicate readily. By contrast, practically no coupling (0-8%) is detectable between heterologous insect cell lines (Homopteran or Lepidopteran) and vertebrate cells (mammalian myocardial or 3T3 cells). No gap junctions have been observed between arthropod and vertebrate cell types, even though the heterologous cells may be separated by less than 10 nm. In additional studies, a low incidence of coupling was found between heterologous insect cell lines derived from different arthropod orders. However, extensive coupling was detected between insect cell lines that are derived from the same order (Homoptera). These observations suggest that there is little or no apparent specificity for communication between vertebrate cells in culture that express the same gap junctional phenotype, while there is a definite communication specificity that exists between arthropod cells in culture.

Animals↗
PubMed1977

Cell-to-cell communication and myogenesis.

Cell-to-cell communication was characterized in prefusion chick embryo myoblast cultures, and it was determined that the prefusion myoblasts can interact via gap junctions, ionic coupling, and metabolic coupling. The biological relevance of this communication was supported by the detection of gap junctions between myoblasts in embryonic muscle. Communication was also examined in fusion-arrested cultures to determine its potential relationship to fusion competency. In cultures that were fusion arrested by treatment with either 1.8 mM ethyleneglycolbis-(beta-aminoethyl ether)N,N'-tetraacetic acid (EGTA), 3.3 X 10(-6) M 5-bromodeoxyuridine (BUdR), or 1 microgram/ml cycloheximide (CHX), both gap junctions and ionic coupling were present. Therefore, it is possible to conclude that cell communication is not a sufficient property by itself, to generate fusion between myob-asts. The potential role of communication in myogenesis is discusssed with respect to these observations.

Cell Communication↗
PubMed1976

Role of Ca2+ and Mg2+ in some human neutrophil functions as indicated by ionophore A23187.

Studies with the divalent cation ionophore A23187 suggest that both Ca2+ and Mg2+ ion influx play a role in human peripheral blood neutrophil function. Degranulation of neutrophils occurred at ionophore concentrations of 10(-5) M and was Ca2+ but not Mg2+ dependent. Modulation of neutrophil chemotaxis was enhanced optimally by 10(-7) M ionophore and was both Ca2+ and Mg2+ dependent. Concentrations of ionophore as low as 10(-12) M seemed to sensitize the cells to a concentration of phorbol myristate acetate which by itself was not chemotactic. These findings also indicate that factors other than Ca2+ or increases in cyclic nucleotides are important to initiation and modulation of neutrophil function.

Anti-Bacterial Agents↗
PubMed1975

Great vessel, cardiac chamber, and wall growth patterns in normal children.

The purpose of this study was to establish normal echocardiographic measurements of valvular motion, cavity dimensions, great vessel diameters, and right, left and septal wall thicknesses of children ranging in size from infants to full growth. The study group was composed of 205 normal, healthy children for whom echocardiograms and subsequent measurements were performed in a standardized manner. The following measurements were performed: left ventricular end-diastolic and end-systolic dimension, right ventricular end-diastolic cavity dimension, right ventricular end-diastolic anterior wall thickness, left ventricular end-diastolic posterior wall thickness, ventricular septal end-diastolic thickness, maximal left atrail dimension, end-diastolic aortic and pulmonary artery diameter, end-diastolic cardiac and septal depth, maximal aortic leaflet separation, and maximal anterior mitral and anterior tricupsid amplitude. Data are grouped into the fifth, fiftieth, and ninety-fifty percentiles according to body surface area. These graphs allow measurements of a single patient to be compared to normal measurements of individuals with similar body surface area.

Aorta↗
PubMedDate not supplied

Iodixanol pharmacokinetics in children.

The objective of this report was to study the elimination pharmacokinetics of iodixanol in children. Iodixanol (Visipaque, Nycomed Inc., Wayne, PA, USA) is a new iso-osmolar iodinated radiocontrast agent. We hypothesized that elimination of this agent would be dependent on age-related differences in renal clearance. Seven centers enrolled 43 patients. Cardiac catheterization was performed in 41 patients and cranial computed tomography in 2. Patients were entered into 5 age groups: newborn to <2 months, 2 to <6 months, 6 months to <1 year, 1 to <3 years, and 3 to 6 months of age that is comparable to normal adults. Prolonged elimination in children <6 months of age is related to renal immaturity.

Age Factors↗