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Biomedical subjects

S Chang

Publications and source records attributed to S Chang.

At least 433 records · Page 24Linked to original sources
PubMed1976

Electron beam ionization mass fragmentographic analysis of tricyclic antidepressants in human plasma.

A method for the measurement, in human plasma, of all tertiary and secondary tricyclic antidepressants prescribed in the United States is described. The method uses electron beam ionization GLC-mass spectrometry, employing a computer-controlled multiple-ion detector. This method, mass fragmentography, is used with internal standards for each drug. Plasma levels to as low as 10 ng/ml of the following drugs can be measured: amitriptyline, nortriptyline, doxepin, desmethyldoxepin, imipramine, desipramine, and protriptyline. Deuterium-labeled amitriptyline and imipramine are used as internal standards for those two drugs; for the other drugs, deuterated amitriptyline, nortriptyline, desmethyldoxepin, or desipramine is used. The method can measure up to 15 samples/hr, making it practical for large-scale studies of these drugs in patients. Spectra of each drug and examples of their analysis are given.

Adult↗
PubMed1976

Role of echocardiography in patients with coronary artery disease.

Impaired left ventricular performance, one of the hallmarks of coronary artery disease, can be detected by echocardiography in various ways. One of these approaches is the recording of abnormal wall motion. Because of the way in which the left ventricle can be examined echocardiographically, this technique has the capability of detecting regional wall abnormalities. In fact echocardiography is probably the most sensitive technique available, including even contrast ventriculography, for the detection of akinetic, hypokinetic or dyskinetic wall segments. With increasing experience it is apparent that more areas of the left ventricle can be examined echocardiographically than had previously been thought possible. Newer techniques include directing the ultrasonic beam not only through the body of the left ventricle but also toward the apical portion of the ventricle near the vicinity of the papillary muscles. In addition the true anterior left ventricular wall can be examined by moving the transducer laterally away from the left sternal border. Yet another approach utilizes a subxiphoid position for the transducer while the ultrasonic beam is directed through the medial portion of the septum and posterolateral wall of the left ventricle. M-mode scanning techniques together with recently developed cross-sectional echocardiographic instruments give great promise of improved detection of abnormalities of ventricular shape, especially the presence of aneurysms. The cross-sectional approach makes it possible to examine the left ventricular apex, an area virtually impossible to record with M-mode echocardiography. Recording of left ventricular dimensions and abnormal mitral valve motion may help in assessing overall left ventricular performance. A dilated left ventricular dimension in the vicinity of the mitral valve seems to be an ominous finding both in patients with acute myocardial infarction and in patients with chronic coronary disease being considered for possible surgery. Another echocardiographic sign of abnormal ventricular performance is altered closure of the mitral valve, which reflects a significantly elevated left ventricular diastolic pressure. These echocardiographic techniques are still in the investigational stages and are more technically difficult than the usual echocardiographic applications. However, the preliminary data are encouraging and make us hopeful that echocardiography will prove to be an important tool in the overall evaluation of the left ventricle in patients with coronary artery disease.

Coronary Disease↗
PubMed1976

Localization of left ventricular outflow obstruction by cross-sectional echocardiography.

Cross-sectional echocardiographic studies were performed using a high resolution real time mechanical sector scanner in 70 patients with left ventricular outflow obstruction. Seven separate obstructive patterns were recorded in these patients. An area of aortic narrowing just distal to the aortic valve at the superior border of the left atrium was noted with supravalvular aortic stenosis. With congenital valvular aortic stenosis there was an increase in echo production by the thickened aortic leaflets. During systole these prominent leaflet echoes curved inward toward the center of the aortic root reflecting the systolic doming of the valve. With calcific aortic stenosis, the calcification produced an area of dense linear echoes attached in varying degrees to either the anterior or posterior border of the aortic root. At the subvalvular level three obstructive patterns were recorded; with a discrete subvalvular obstructive membrane two linear echoes apparently produced by the inner margins of the obstructing membrane were recorded in the outflow tract. With more extensive fibromuscular narrowing of the subvalvular area, there was inward bowing of the echoes from both the anterior and posterior walls of the outflow tract. In one case this was a dense shelf-like mass of echoes extending downward from the basal portion of the interventricular septum toward the mid-portion of the anterior mitral leaflet with corresponding systolic anterior motion of the mitral leaflet. In patients with idiopathic hypertrophic subaortic stenosis there was systolic anterior motion of the anterior mitral leaflet beginning just distal to the point of coaptation of the mitral leaflets and extending distally toward the papillary muscles. This report suggests that the enlarged field of vision and spatial orientation provided by the cross-sectional echocardiographic technic should improve our ability to record and characterize areas of obstruction to left ventricular outflow.

Aortic Stenosis, Subvalvular↗
PubMed1976

M-mode echocardiography in the evaluation of patients for aneurysmectomy.

In order to determine whether echocardiography could be useful in predicting surgical mortality of aneurysmectomy, preoperative condensed M-mode echocardiographic scans were taken from both mid (standard position) and low (nearer apex) intercostal spaces and/or from the subxiphoid area in eighteen patients who were sent to surgery for aneurysmectomy. Eleven of the eighteen patients survived aneurysmectomy. All eleven had mid left ventricular dimensions less than 3.3 cm/m2 and low dimensions of 3.8 cm/m2 or less. Of the seven patients who died, the mid and low left ventricular dimensions exceeded 3.3 cm/m2 and 3.8 cm/m2, respectively, with one exception. The combination of abnormal mitral valve closure, a dilated mid dimension and lack of normal motion in opposing wall segments was only seen in six nonsurvivors. Echocardiography can provide information concerning the state of the left ventricle in patients with ventricular aneurysms and these findings may be helpful in predicting surgical mortality for aneurysmectomy.

Adult↗
PubMed1976

Echocardiographic manifestations of aortic cusp rupture in a myxomatous aortic valve.

A 16-year-old pregnant black girl who had spontaneous perforation of the aortic valve associated with myxomatous aortic valvular degeneration is presented. The echocardiogram revealed chaotic systolic motion of one of the aortic cusps, diastolic aortic valvular fluttering, and abnormal diastolic echoes in the left ventricular outflow tract. The report illustrates that the echocardiographic features associated with valvular vegetations are not specific for infectious endocarditis.

Adolescent↗
PubMed1975

The nucleotide sequence of a precursor to the glycine- and threonine-specific transfer ribonucleic acids of Escherichia coli.

The primary nucleotide sequence of an Escherichia coli tRNA precursor molecule has been determined. This precursor RNA, specified by the transducing phage lambdah80dglyTsuA36 thrT tyrT, accumulates in a mutant strain temperature-sensitive for RNase P activity. The 170-nucleotide precursor RNA is processed by E. coli extracts to form mature tRNA Gly 2 suA36 and tRNA Thr ACU/C. The sequence of the precursor is pG-U-U-C-C-A-G-G-A-U-G-C-G-G-G-C-A-U-C-G-U-A-U-A-A-U-G-G-C-U-A-U-U-A-C-C-U-C-A-G-C-C-U-N-C-U-A-A-G-C-U-G-A-U-G-A-U-G-C-G-G-G-T-psi-C-G-A-U-U-C-C-C-G-C-U-G-C-C-C-G-C-U-C-C-A-A-G-A-U-G-U-G-C-U-G-A-U-A-U-A-G-C-U-C-A-G-D-D-G-G-D-A-G-A-G-C-G-C-A-C-C-C-U-U-G-G-U-mt6A-A-G-G-G-U-G-A-G-m7G-U-C-G-G-C-A-G-T-psi-C-G-A-A-U-C-U-G-C-C-U-A-U-C-A-G-C-A-C-C-A-C-U-UOH(tRNA sequences are italicized). It contains the entire primary nucleotide sequences of tRNA Gly2 suA36 and tRNA Thr ACU/C, including the common 3'-terminal sequence, CCA. Nineteen additional nucleotides are present, with 10 at the 5' end, 3 at the 3' end, and the remaining 6 in the inter-tRNA spacer region. RNase P cleaves the precursor specifically at the 5' ends of the mature tRNA sequences.

Autoradiography↗
PubMed1975

Quantum chemical study of relative reactivities of a series of amines and nitriles: relevance to prebiotic chemistry.

Using the Iterative Extended Hucken Theory (IEHT) calculations of the elctron distribution and orbital energies of a series of thirteen amines, nitriles and amino-nitriles relevant to prebiotic and cosmo-chemistry have been carried out. Ground state properties such as the energy and nature of the highest occupied (HOMO) and lowest empty (LEMO) molecular orbitals, net atomic charges and number of non-bonding electrons have been identified as criteria for correlating the relative nucleophilicity of amine and nitrile nitrogens and the electrophilicity of nitrile and other unsaturated carbon atoms. The results of such correlations can be partially verified by known chemical behavior of these compounds and are used to predict and understand their role in prebiotic organic synthesis.

Amines↗
PubMed1975

Intracavitary echoes in patients with mitral prosthetic valves.

In the course of doing routine echocardiograms on patients with mitral prosthetic valves, we observed peculiar intracavitary echoes within the left ventricle. Of the 36 valves studied in 31 different patients, 14 echocardiograms demonstrated the abnormal intracavitary echoes and 22 did not. The presence of mitral insufficiency, atrial fibrillation, systemic emboli and warfarin sodium (Coumadin) therapy were roughly equal in the two groups. A higher percentage of abnormal intracavitary echoes occurred in patients with a hemoglobin less than 11 gm/100 ml, other prosthetic valves, cloth covered valves, low platelets, and functional class III-IV. Although this study does not clarify the origin of these abnormal echoes, it is possible that they originate from particulate matter such as tiny fibrin clots or fibers from the cloth covering of the valve.

Echocardiography↗
PubMed1975

Echocardiographic differentiation of infundibular from valvular pulmonary stenosis.

Echocardiographic tracings of the pulmonary valve were examined in 24 normal subjects, 16 patients with valvular pulmonary stenosis and 3 patients with infundibular pulmonary stenosis. In normal subjects, atrial contraction produced a slight posterior opening motion of the pulmonary valve leaflet (a wave). This presystolic opening motion (a wave) varied with respiration, and maximal a wave depth recorded during quiet inspiration (Amax) averaged 3.7 plus or minus 1.2 (standard error of the mean) mm (range 2 to 7 mm). In the 10 cases with moderate or severe valvular pulmonary stenosis, increased force of right atrial contraction and elevated right ventricular end-diastolic pressure resulted in an increased posterior or opening motion of the pulmonary valve leaflet, and Amax averaged 9.6 plus or minus 2.0 mm (range 8 to 13 mm, P less than 0.001 versus normal). When both anterior and posterior leaflets were recorded, presystolic opening or doming of the valve was observed. In six cases of mild valvular pulmonary stenosis, Amax averaged 4 plus or minus 2.5 mm (not significant). In patients with infundibular pulmonary stenosis, marked chaotic systolic fluttering of the valve leaflet, which lies in the turbulent stream of blood distal to the obstruction, was recorded. This finding was never seen with valvular pulmonary stenosis. In two cases of mild infundibular pulmonary stenosis, the amplitude of presystolic opening motion was within the normal range of 3 and 7 mm. In one case of severe infundibular pulmonary stenosis, no presystolic opening motion was recorded, thus suggesting that the small pressure changes produced by atrial systole failed to reach the valve leaflets. Echocardiography, therefore, should be of use in differentiating valvular from infundibular pulmonary stenosis.

Adolescent↗
PubMed1975

Human lymphocyte antigen, HL-A27, in Japanese patients with ankylosing spondylitis.

A high association of HL-A27 specificity with ankylosing spondylitis was found in Japanese patients in spite of a very low frequency of this specificity in a normal Japanese population. These findings coincide well with those in Caucasian patients, and indicate the strong relationship between the susceptibility to ankylosing spondylitis and HL-A27 specificity beyond racial differences. No particular HL-A patterns were noted in patients with the ossification of the posterior longitudinal ligament of the cervical vertebrae. This observation provides an evidence that this disease is etiologically different from ankylosing spondylitis.

HLA Antigens↗
PubMed1975

Pulmonary valve echo motion in pulmonary regurgitation.

Four cases are presented to illustrate the echo patterns of pulmonary valve motion in patients with pulmonary regurgitation caused by pulmonary hypertension, idiopathic dilatation of the pulmonary artery, or congenital absence of the pulmonary valve or in association with pulmonary stenosis. Absence of the pulmonary 'a' wave, fluttering of the e-f slope, and midsystolic closure or 'notching' of the valve were noted with pulmonary hypertension. In the case with idiopathic dilatation of the pulmonary artery a normal echo pattern of pulmonary valve motion along with distinct dilatation of the pulmonary artery at the valvular level were present. Pronounced dilatation and systolic expansion of the pulmonary artery along with dilatation of the right ventricle were seen with congenital absence of the pulmonary valve. No pulmonary valve could be demonstrated on multiple scans from the right ventricle to pulmonary artery. In Case 4 large 'a' waves (14 mm) were noted, indicating a reversal of the normal end-diastolic gradient across the valve and suggesting that pulmonary regurgitation in this case was associated with right ventricular outflow obstruction. Study of the echo pattern of pulmonary valve motion may therefore provide useful information in establishing the cause of pulmonary regurgitation.

Adolescent↗
PubMed1975

Premature pulmonic valve opening following sinus of Valsalva aneurysm rupture into the right atrium.

Echocardiographic features of a patient with sinus of Valsalva aneurysm rupture into the right atrium are described. The aneurysm presented as a dense echo-producing mass in the right atrium which descended into the tricuspid orifice during diastole and withdrew back into the atrium during ventricular systole. Pulmonic valve exho motion demonstrated early diastolic pulmonic valve opening indicating an early right ventricular diastolic pressure rise exceeding simultaneous pulmonary artery pressure. Since the aorta is the only source of early diastolic pressure in excess of pulmonary artery pressure available to the right heart, this finding of early diastolic pulmonic valve opening indicated the presence of a fistula between the aorta and right heart. Other interesting echocardiographic features of this case are also presented.

Adult↗
PubMed1975

Cross-sectional echocardiography in assessing the severity of valvular aortic stenosis.

Real-time, cross-sectional echocardiograms were recorded in 28 consecutive adult patients with valvular aortic stenosis using a high resolution, mechanical sector scanner. Using the cross-sectional technique, the aortic valve orifice diameter was recorded in each of the 28 patients. With M-mode echocardiographic examination of these same patients, this value could be estimated in only 21 of these 28 patients (75%). The maximum aortic valve diameter recorded during the cross-sectional study averaged 7.9 +/- 1.8 mm (range 4-11 mm) in 15 patients with severe aortic stenosis; 11.6 +/- 2.3 mm (range 9-15 mm) in five patients with moderate aortic stenosis; 16.9 +/- 2.0 mm (range 14-20 mm) in eight patients with mild aortic stenosis; and 20.5 +/- 2.8 mm (range 15-26 mm) in 25 patients with no evidence of aortic valve disease. Comparing the means of these groups yielded the following: severe vs moderate P less than 0.005; moderate vs mild P less than 0.001; and mild vs normal P less than 0.001. Although there was some overlap between the individual groups, a clear separation existed between patients with severe and mild aortic stenosis. In addition, the group of patients in whom surgical intervention was recommended was also separated from the other subjects. When the aortic valve orifice was recorded using the M-mode technique, there was also a good correlation with the severity of the stenosis; however, the tendency of the M-mode study to overestimate severity in individual patients with calcific aortic stenosis and to underestimate severity in congenital aortic stenosis was again demonstrated. This study suggests that real-time, high resolution, cross-sectional echocardiography should be valuable in the noninvasive assessment of patients with aortic stenosis.

Aortic Valve Stenosis↗