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Biomedical subjects

S Kaplan

Publications and source records attributed to S Kaplan.

At least 487 records · Page 27Linked to original sources
PubMed1975

The association of fixed and dynamic left ventricular outflow obstruction.

Twelve patients were investigated echocardiographically and angiographically and were shown to have severe fixed obstruction to the left ventricular outflow tract. Eight had valvular stenosis, and four had discrete subvalvular membranes. Two of the patients had additional dynamic obstruction of the left ventricular outflow tract. This was recognized preoperatively by echocardiography because of abnormal systolic motion of the mitral leaflet. At the time of definitive surgery for relief of the fixed obstruction, the additional dynamic obstruction was identified and treated, since persistent residual obstruction may lead to death in the immediate postoperative period or to long-term symptoms. The dynamic left ventricular outflow obstruction is probably a result of the hypertrophy produced by the fixed obstruction.

Adolescent↗
PubMed1975

The critically ill premature infant with patent ductus arteriosus and pulmonary disease-an echocardiographic assessment.

The effect of left-right shunting upon left ventricular and atrial dimensions was assessed by means of 129 serial echocardiographic studies in 37 premature infants with patent ductus arterisus. The cardiac dimensions of asymptomatic premature infants and those with pulmonary disease were similar and served as control subjects. Left cardiac dimensions were enlarged in infants with significant PDA. Dimensions were greatest in surgically treated infants (post-operatively they returned rapidly to normal) in contrast with the persistent enlargement observed in some medically treated infants. Serial echocardiography was a valuable adjunct to clinical assessment of the course of PDA in premature infants with pulmonary disease.

Cardiomegaly↗
PubMed1975

Excision of bacteriophage lambda from a site in the arabinose B gene.

A lambda lysogen with the prophage inserted into the arabinose B gene of Escherichia coli strain K-12 has been prepared. Induction of the phage from this lysogen yields viable phage at a frequency 4 X 10(-6) that found for induction of lysogens with phage inserted at the normal attachment site. Over 30% of the phage particles induced from the insertion in ara are arabinose-transducing phage. The excision end points of 62 independently isolated, nondefective araC-transducing phage containing less than the entire araC gene were genetically determined and were found to be randomly distributed through the araC gene. The amount of arabinose deoxyribonucleic acid contained on four selected transducing phage was determined by electron microscopy of deoxyribonucleic acid heteroduplexes, providing a physical map of the araC gene. The efficiency with which these phage transduce araC and araB point mutations was found to be approximately proportional to the homology length available for recombination.

Arabinose↗
PubMed1975

Echographic determination of left ventricular volumes in pediatric patients.

The purpose of this study was to validate the accuracy of determining left ventricular (LV) volumes by echocardiography in infants and children. Thirty-one patients between the ages of two months and 15 years underwent left ventriculography (biplane antero-posterior and lateral cine). Ventricular volumes using an ellipsoidal model were calculated for end diastole from the cineangiograms. There was a strong correlation (r = 0.856) between the echographic minor dimension (Be) and the minor lateral cine dimension (Bc) at end diastole. A similar correlation (r = 0.889) existed between the LV volume in end diastole measured by cineangiography and Be. The correlation coefficient between the echo minor dimension and the lateral minor cine dimension in end systole was 0.753. A relation between ejection fraction (EF) and the echo minor dimension measurements in end diastole and end systole was formulated, which permitted estimation of the EF from the echo measurements. As a result of this study, it was concluded that the LV minor dimension can be measured reliably by echocardiography in children and from these measurements LV volumes, ejection fraction, and hence, stroke volume can be estimated.

Adolescent↗
PubMed1975

Measurement of right and left ventricular systolic time intervals by echocardiography.

One of the noninvasive methods of evaluating left ventricular performance is the measurement of left ventricular systolic time intervals (LVSTI). However, noninvasive measurement of right ventricular systole by this technique has been unreliable because of the inability to accurately time the onset of right ventricular ejection. Excellent correlation of LVSTI measured from the carotid pulse and those determined from the echocardiogram was demonstrated in 15 patients. STI of the right ventricle (RVSTI) were measured in a similar fashion from the pulmonary valve echo in 11 normal children. Right ventricular ejection time (RVET) was longer than left ventricular injection time (LVET). Right ventricular pre-ejection period and RPEP was shorter than left ventricular pre-ejection period (LPEP). In 15 children with transposition of the great arteries (TGA) the situation was reversed. RVET was shortened and RPEP was prolonged as the right ventricle contracted against systemic resistance; whereas, the LVET lengthened and LPEP shortened with ejection into a low pressure pulmonary circuit. Our studies in a total of 41 patients indicate the accurate, noninvasive measurement of right, as well as left, ventricular STI can be obtained with the use of echocardiography.

Adolescent↗
PubMed1975

The echocardiographic assessment of pulmonary artery pressure and pulmonary vascular resistance.

Serial assessment of the status of the pulmonary vascular bed requires bed requires cardiac catheterization. We have demonstrated the right ventricular systolic time intervals (RVSTI) may be measured from the pulmonary valve echo. The right ventricular ejection time (RVET) and right pre-ejection period (RPEP) were measured in 45 normal patients. The RVET and RPEP decreased with increasing heart rate but increased with age. The RPEP/RVET, however, was uninfluenced by either age or heart rate. The RPEP/RVET was, therefore, determined from the pulmonary valve echo in 64 patients with congenital heart disease who underwent cardiac catheterization. Increased pulmonary artery diastolic pressure (PADP), pulmonary vascular resistance (PADP), pulmonary vascular resistance (PVR) and mean pulmonary artery pressure (MPAP) resulted inan increased RPEP/RVET. The use of the RPEP/RVET permitted the serial echographic evaluation of the pulmonary vascular bed in selected patients; marked elevation of the ratio indicated the presence of pulmonary hypertension.

Adolescent↗
PubMed1975

Unexpected cardiac arrest in patients after surgical correction of tetralogy of Fallot.

Four of 220 patients without bifasicular block (complete right bundle branch block and left anterior hemiblock) or transient complete heart block immediately after surgery had an unexpected cardiac arrest one to 15 years after satisfactory surgical repair of tetralogy of Fallot. The postoperative electrocardiograms (ECG) revealed complete right bundle branch block in two patients and no intraventricle conduction abnormality in two patients. Each of the four patients had premature ventricular contractions on previous postoperative ECG. The cardiac arrest occurred during normal activity in three patients and mild exercise in one. Following the cardiac arrest, three patients died and one patient survived. Eighteen months before the cardiac arrest, the survivor had a stress test which revealed multifocal premature ventricular contractions with short bursts of ventricular tachycardia after exercise. This ventricular arrhythmia was suppressed with quinidine therapy. Although complete heart block cannot be excluded in these four patients, we reasoned that the cardiac arrests were probably preceded by ventricular tachyarrhythmia. Because of this experience, we believe that any patient who has had intraventricular surgery should be evaluated for ventricular arrhythmia. If frequent premature ventricular contractions or serious ventricular arrhythmias are documented, we seriously consider antiarrhythmic therapy in an attempt to prevent ventricular tachyarrhythmias and sudden death.

Adolescent↗
PubMed1975

Emulsions of perfluorinated solvents for intravascular gas transport.

During the past several years we have progressed from the use of perfluorinated substances, which were good gas solvents but often produced unexpected physiological reactions, to a point where emulsions of pure perfluorinated substances can be made in a reproducible way. A standardized method of making emulsions has now been developed. The physical properties of the perfluorinated substances needed to make useful emulsions have been defined. Specifically, perfluorinated substances having vapor pressures above about 40 torr must be avoided as they produce pulmonary gas embolism; also lower boiling components having vapor pressures above about 40 torr must be excluded. The relationship between chemical structure and several physiological and pharmacological effects has been delineated. Perfluorinated substances containing only carbon and fluorine, or those containing carbon, fluorine, and either bromine or iodine have reasonably short dwell times in the liver. Perfluorinated iodo- and bromo-compounds dissolve oxygen and are radiopaque. Present iodo-perfluorinates are unstable in the presence of light. Perfluorodecalin can enter and leave the liver without changing the liver's ultrastructure. Both egg phospholipid and Pluronic F68 are useful in making perfluorodecalin emulsions. Perfluorodimethyladamantane makes a fine-particle stable emulsion. There is a bright future for perfluorinated substances in a number of areas of research in biology and medicine.

Animals↗
PubMed1974

Topology and growth of the intracytoplasmic membrane system of Rhodopseudomonas spheroides: protein, chlorophyll, and phospholipid insertion into steady-state anaerobic cells.

An equilibrium density gradient centrifugation study involving the separation of "old" and "new" membranes has been developed to determine the manner in which protein, lipid, and chlorophyll are incorporated into growing intracytoplasmic membranes (chromatophores) of Rhodopseudomonas spheroides. Chromatophores derived from cells grown in an H(2)O-medium had a density of 1.175 to 1.180 g/cm(3) and were readily separable from chromatophores having a density of 1.220 to 1.230 isolated from cells grown in a 70% D(2)O-medium. After a shift from "D(2)O-" to "H(2)O"-based media, only hybrid chromatophores derived from a combination of "heavy" (old) and "light" (new) chromatophore material could be detected. The experimentally determined, median density values for the growing intracytoplasmic membrane system followed a theoretically determined profile which was calculated from the density of full "heavy" and full "light" material assuming random, homogeneous incorporation of new material into old membrane. The distribution of the radioactive labels for protein (leucine) and chlorophyll (delta-aminolevulinic acid) were identical and showed a reproducible displacement of the "old" material to the heavy side of the optical density at 365 nm (OD(365)) absorbance and a displacement of the "new" material to the light side of the OD(365) absorbance profile. Specific phospholipid growth showed no displacement for either the "old" or "new" material from the median absorbance profile.

Acetates↗