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Biomedical subjects

S Chang

Publications and source records attributed to S Chang.

At least 415 records · Page 23Linked to original sources
PubMed1978

Prediction of in vivo red cell/plasma Li+ ratios by in vitro methods.

Two incubation procedures were used for the determination, in vitro, of the steady-state Li+ ratio between red cells and external media. The Li+ ratio in vitro determined prior to Li+ therapy correlates significantly with the subsequent ratio in vivo between red cells and plasma in patients treated with Li+. The Li+ ratio determined in vitro in patients during Li+ therapy was significantly higher than the value determined during the pretreatment, drug-free period that correlated significantly with Li+ ratios in vivo. The in vitro procedure used thus could be applied in the prediction of the in vivo Li+ ratio, and possibly of the response to Li+, in patients before treatment is begun. It also could be used for studies on abnormalities and on the genetics of Li+ transport in affective illness.

Bicarbonates↗
PubMed1978

The echocardiographic correlate of a systolic click appearing after open mitral commissurotomy.

An echocardiographic correlate for a post-valvulotomy mid-systolic click is described. Simultaneous echocardiographic and phonocardiographic studies demonstrated that the click was temporally related to a sudden midsystolic posterior motion of part of the mitral valve apparatus. This temporal relationship suggests that the sudden change in position of portions of the mitral valve resulted in the loud midsystolic click. In our patient the sudden leaflet movement associated with the click was apparently a localized abnormality.

Adult↗
PubMed1978

Adrenal androgens in patients with chronic marked elevation of prolactin.

It has been postulated, based on data in animals and the fact that the cortisol-adrenal androgen ratio is different before and after adrenarche, that prolactin (Prl) may modulate adrenal androgen secretion. As one way of testing this hypothesis, cortisol, androstenedione (A), dehydroepiandrosterone (DHA), and dehydroepiandrosterone sulphate (DHAS) were measured by radioimmunoassay in the sera of thirteen patients with suspected or proven pituitary tumours and marked chronic elevations of serum Prl (range 68-990 ng/ml, mean 198.9 ng/ml). Values for cortisol, A, DHA, and DHAS were not significantly different between the groups of normal controls and patients with elevated Prl concentrations. This is interpreted as negative evidence for the theoretical connection between Prl and adrenal androgen secretion.

Androstenedione↗
PubMed1978

Malfunction of Cutter-Smeloff mitral prosthesis. An echocardiographic diagnosis.

Progression of intermittent partial or total impaction of the poppet from a prosthetic mitral valve may be difficult to evaluate in patients with chronic obstructive pulmonary disease and atrial fibrillation. Heart sounds may be distant; opening and closing clicks of the poppet are muffled and irregular. Echocardiography provides a noninvasive method to detect early prosthetic malfunction at a time when the patient is clinically asymptomatic.

Atrial Fibrillation↗
PubMed1977

Aortic stenosis: echocardiographic cusp separation and surgical description of aortic valve in 22 patients.

Diminished echocardiographic aortic cusp separation is used as one indicator of the severity of aortic stenosis. To test the validity of this index, 22 patients--12 (55 percent) with isolated aortic valve disease and 10 (45 percent) with aortic stenosis associated with mitral or coronary artery disease--underwent M mode echocardiographic examination before aortic valve replacement. Tracings of diagnostic quality were obtained without difficulty from all 22 patients. Cardiac catheterization was performed in 21 patients. Echocardiographic cusp separation was measured from the apparent mid-systolic orifice and from the outer periphery of the anterior cusp to the outer periphery of the posterior cusp (maximal peripheral cusp separation). Mid-systolic cusp separation varied in nearly every patient, depending on the angle of leaflet presentation to the ultrasonic beam. Maximal peripheral cusp separation measured 16 mm in 18 of 22 patients (82 percent); it indicated neither the severity of the aortic stenosis as documented with cardiac catheterization nor the mobility of the cusps seen at operation. The surgical and echocardiographic descriptions of leaflet and aortic root calcification were similar. In situ examination of aortic cusp separation indicated that diseased aortic valves are not comparable with normal valves or valves with uncomplicated congenital obstruction. The aortic leaflets were curled, fused, calcified and deformed from their natural state of coaptation. Abnormal thickening and limited or eccentric mobility of the aortic leaflets were useful indicators of the cause of valve disease, but cusp deformity secondary to aortic stenosis invalidated mid-systolic cusp separation and maximal peripheral cusp separation as indicators of the severity of aortic stenosis.

Adult↗
PubMed1977

In vivo site-specific genetic recombination promoted by the EcoRI restriction endonuclease.

Site-specific genetic recombinations promoted in vivo by the EcoRI endonuclease has been demonstrated by using constructed hybrid plasmids in which the chloramphenicol resistance gene was inactivated by insertion of DNA fragments at an EcoRI site within the gene. Such recombination can involve either the joining of intracellularly generated cohesive termini of the same DNA fragment or intermolecular ligation of different DNA fragments. DNA cleavage and ligation in vivo are precise: recombinant DNA molecules show functional continuity of the gene sequence cleaved by the enzyme and regeneration of nucleotide recognition sites for both the EcoRI endonuclease and the EcoRI DNA methylase. In other experiments, EcoRI-generated fragments of eukaryotic DNA that had not been modified by the Escherichia coli K methylase were shown to be taken up by bacterial cells and to undergo intracellular ligation to segments of bacterial plasmid DNA.

DNA Restriction Enzymes↗
PubMed1977

Immunohistological analysis of intravascular agglutination in a case of ABO incompatible blood transfusion by means of mixed cell agglutination reaction.

Applicability of the mixed cell agglutination reaction (MCAR of Davidsohn) in histological examination was tested in a case of ABO incompatible blood transfusion, who had died of severe head injury two days after an accident. Massively disseminated intravascular aggregation of erythrocytes was identified as immune agglutination by the modified method of MCAR (ISHIYAMA & OKADA) with precise knowledge of topographic isoantigen localization in tissues. The immune specific agglutination mimics intravascular changes such as hyperemia, stagnation and hemorrhage derived from various circulatory disturbances obtained in routine autopsy materials.

ABO Blood-Group System↗
PubMed1977

Cholinergic influences in tardive dyskinesia.

The authors conducted placebo-controlled double-blind studies of physostigmine, choline, and deanol in 12 patients with tardive dyskinesia. Physostigmine and choline both had a positive therapeutic effect on tardive dyskinesia, but the authors note that interpretation of these results is not entirely clear because they found that the sedation effect of physostigmine may nonspecifically reduce the intensity of tardive dyskinesia symptoms. Deanol was not found to be effective in this group of patients; the authors suggest that this drug should not be assumed to be generally effective unless effectiveness is verified by a large placebo-controlled double-blind study.

Acetylcholine↗
PubMed1977

Electrophysiological (H-reflex) studies of patients with tardive dyskinesia.

The authors studied the H-reflex recovery curves of 31 schizophrenic patients with tardive dyskinesia in response to acute administrations of apomorphine, amphetamine, or physostigmine and compared them with curves of chronic schizophrenic patients without tardive dyskinesia and normal volunteers. Their most unexpected finding was the absence of an H-reflex in 9 of the 31 patients with tardive dyskinesia. They also found a relationship between severity of tardive dyskinesia and the value of the facilitatory peak Hchi: patients with more severe tardive dyskinesia symptoms had significantly higher values for Hchi.

Amphetamine↗
PubMed1977

Influence of age and stomach function on serum vitamin B12 concentration.

Serum vitamin B12 (B12), maximal gastric acid output (MAO), and B12 absorption were determined in 82 subjects, age 32 to 85 years, who had normal absorption of radiocyanocobalamin. In 46 of the patients the gastric intrinsic factor (IF) was also measured. Serum B12 concentration and MAO varied widely in all age groups from abnormally low to definitely normal. The mean values for serum B12 and MAO, however, declined very similarly with advancing age owing to an increased incidence of low values for these two measurerment in the aged. There was no significant fall in the mean B12 absorption or IF secretion as a function of old age. Achlorhydric and hypochlorhydric patients invariably had lower mean serum B12 concentrations than those with adequate MAO. Conversely, patients with normal MAO all had normal serum B12 levels. Serum B12 concentration, although correlating with both MAO and IF secretion, showed a closer relationship to the former than to the latter. These findings suggest that the stomach, aside from producing the IF, plays an important role in maintaining a normal serum B12 concentration.

Adult↗
PubMed1977

Diabetic ketoacidosis with retinal tear.

A 59-year-old women with no previous history of diabetes mellitus was admitted in diabetic ketoacidosis. Ultrasonic biometry was used to measure axial vitreous length during therapy. Vitreous length increased from 14.09 mm shortly after admission to 14.26 mm (p less than 0.05) when the episode of diabetic ketoacidosis cleared. An interesting finding was the presence of a horseshoe-shaped retinal tear after the patient was discharged. Severe dehydration with resultant shrinkage of the vitreous compartment may provide sufficient vitreoretinal traction to cause a retinal tear. In addition, an estimate of volume change showed a comparable decrease in vitreous volume seen with therapy using osmotic agents measured in rabbits.

Diabetic Ketoacidosis↗
PubMed1976

The possible role of solid surface area in condensation reactions during chemical evolution: reevaluation.

Published data on adsorption and condensation of amino acids, purine and pyrimidine bases, sugars, nucleosides, and nucleotides are analyzed in connection with Bernal's hypothesis that clays and other minerals may have provided the most likely surface for adsorption and condensation of these molecules in prebiotic times. Using surface concentration and reaction rate as the main criteria for the feasibility of condensation reactions, four types of prebiotic environments were analyzed: (1) an ocean-sediment system, (2) a dehydrated lagoon bed produced by evaporation, (3) the surface of a frozen sediment, and (4) a fluctuating system where hydration (rainstorms, tidal variations, flooding) and dehysration (evaporation) take place in a cyclic manner. With the possible exception of nucleotides, low adsorption of organomonomers on sediment surfaces of a prebiotic ocean (pH 8) is expected, and significant condensation is considered unlikely. In dehydrated and frozen systems, high surface concentrations are probable and condensation is more likely. In fluctuating environments, condensation rates will be enhanced and the size distribution of the oligomers formed during dehydration may be influenced by a "redistribution mechanism" in which adsorbed oligomers and monomers are desorbed and redistributed on the solid surface during the next hydration-dehydration cycle.

Adsorption↗
PubMed1976

Cross-sectional echocardiography in evaluating patients with discrete subaortic stenosis.

Ten patients with discrete subvalvular aortic stenosis were examined using a real time, high resolution cross-sectional echocardiographic scanner. There were two patients (Group I) with a thin discrete subvalvular membrane, five (Group II) with a more extensive area of subvalvular narrowing and three with a residual area of outflow tract obstruction after surgical revision (Group III). In patients with a thin obstructing membrane (Group I), two distinct linear echoes were observed in the outflow tract. These echoes were not continuous with the walls of the outflow tract and showed some dynamic motion during the cardiac cycle. In four of the five patients with diffuse outflow tract narrowing (Group II), a relatively extensive area of inward bowing of both the anterior and posterior margins of the outflow tract was noted. In the fifth case, there was a prominent localized shelf-like increase in thickness of the basal portion of the muscular septum with a corresponding echo projecting anteriorly from the mid-portion of the anterior or mitral leaflet. The three cases examined after surgical revision of the outflow tract (Group III), had different patterns of outflow tract narrowing, but narrowing was clearly demonstrated. This study suggests that cross-sectional echocardiography offers an alternative and probably improved method for the noninvasive visualization of the left ventricular outflow tract.

Adolescent↗
PubMed1976

Pilocarpine therapy in glaucoma: effects on anterior chamber depth and lens thickness in patients receiving long-term therapy.

The effect of pilocarpine hydrochloride on the anterior chamber depth and lens thickness was measured in 20 eyes of patients with chronic open-angle glucoma who were receiving long-term glaucoma therapy with pilocarpine. Measurements were made with high-resolution ultrasonic biometry. This study demonstrated that regardless of their age (58.4 years, average) and the fact that they had been regularly using pilocarpine from two to four times a day, 85% of these patients demonstrated narrowing of the anterior chamber (AC) depth (average, 0.19 mm) and thickening of the lens (average, 0.21 mm) with each instillation of pilocarpine. In approximately 15% of eyes, a repeatable deepening of the AC depth and flattening of the lens was noted.

Administration, Topical↗