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Biomedical subjects

J M Lopez

Publications and source records attributed to J M Lopez.

71 records · Page 4Linked to original sources
PubMed1977

Role of sugar uptake and metabolic intermediates on catabolite repression in Bacillus subtilis.

Many phosphorylated intermediates exert catabolite repression on the enzyme acetoin dehydrogenase in Bacillus subtilis. This was shown with strains that are blocked at different positions in central metabolism when they receive sugars that cannot be metabolized past enzymatic block(s). In the case of sorbitol, transport events were not involved in catabolite repression, for this sugar cannot repress acetoin dehydrogenase in a strain lacking sorbitol dehydrogenase but otherwise able to take up sorbitol. The presence of glucose did not markedly influence the uptake of acetoin.

Acetoin↗
PubMed1976

Diagnosis of Björk-Shiley aortic valve dysfunction by echocardiography.

Echocardiography was performed on 26 patients with prosthetic Björk-Shiley aortic valves (BSAV). Technically satisfactory records were obtained in 22 patients. The systolic displacement of the valve disc varied from 1 to 1.8 cm. (mean, 1.4 cm.). Six patients developed valve dysfunction. Two patients had complete absence of Björk disc motion and dense echoes in the aortic root were noted on the echocardiogram. Extensive clot formation in and around the valve was seen at operation. After clot removal, these two echocardiograms showed excellent disc motion (1.5 and 1.8 cm.). In a third patient with a clotted valve, marked reduction of the velocity of opening and closing of the valve was noted. Three patients had aortic incompetence without evidence of clot formation. Normal disc motion (DM) was observed in all three. A seventh patient presented with a low output state and markedly reduced valve clicks. Echocardiography revealed normal DM with marked dilatation of the left ventricle. These features were confirmed by angiography. We conclude that: (1) satisfactory echocardiograms can be obtained in most patients with BSAV; (2) echocardiography may be a useful method of detecting Björk valve dysfunction.

Adult↗
PubMed1975

Echocardiographic observations on the mechanism of production of the second heart sound.

This investigation was designed to determine the echocardiographic correlates of the aortic and pulmonary components of the second heart sound. Simultaneous recordings of the ECG, phonocardiogram, carotid pulse tracing and the echocardiogram of the aortic valve were made in 54 patients. The tracings were recorded at a paper speed of 100 mm/sec, with 20 msec time lines. Aortic valve closure (AVC) on the echocardiogram occurred before the onset of the aortic component of the second heart sound (A2) in all but two patients. The mean AVC-to-A2 interval was 12 msec with a range of 5 to 25 msec. Simultaneous recordings of the pulmonary valve echocardiogram, ECG, phonocardiogram and carotid pulse tracing were made in 14 patients. Pulmonary valve closure (PVC) on the echocardiogram preceded the pulmonary component of the second sound (P2) in all patients. The mean PVC-2 interval was 60 msec with a range of 30 to 75 msec. We conclude that aortic valve closure and pulmonary valve closure are not directly responsible for the genesis of the second heart sound (S2). These observations are consonant with the theory that S2 is caused by deceleration of columns of blood resulting from semilunar valve closure, throwing the cardiohemic system into vibration.

Adolescent↗
PubMed1975

Echocardiographic detection of tricuspid valve prolapse.

The echocardiographic findings in 12 patients with tricuspid valve prolapse are presented. Eight of these patients had associated mitral valve prolapse. Only one of the above patients had the characteristic physical signs of tricuspid incompetence. Two types of abnormality were noted on the echocardiogram of the tricuspid valve. In eight patients, the systolic segment of the tricuspid valve showed an initial horizontal motion followed by a posterior motion in midsystole. Four patients exhibited posterior motion of the tricuspid valve in early systole, which reached a maximum in midsystole, and this was followed by an anterior motion, thus producing a hammock-like configuration. We conclude that echocardiography is useful in the diagnosis of tricuspid valve prolapse. Since this condition may be associated with clinically significant tricuspid incompetence or bacterial endocarditis, its recognition is of clinical importance.

Adolescent↗
PubMed1975

[Radiological appearances of cancer of the gastric stump (author's transl)].

The authors report 35 cases of primary carcinoma of the gastric stump, describing the technique they use for radiography, noting the main diagnosis signs and discussing the importance of the various methods for their study. They emphasize the importance of periodic post-operative control in these cases.

Adult↗
PubMedDate not supplied

Idiopathic hypertrophic subaortic stenosis in the elderly.

In a 24-month period, 27 patients with idiopathic hypertrophic subaortic stenosis (IHSS), ages 65-80 years, were observed. Diagnoses were made by echocardiography (24 patients), cardiac catheterization (one patient), and both methods (two patients). The most common symptoms were angina (17 patients), dyspnea (13 patients), and syncope (11 patients). Two patients were asymptomatic, while another complained only of vague retrosternal chest discomfort with exertion. One asymptomatic patient had a completely normal physical examination, but electrocardiography (ECG) demonstrated a pattern of left ventricular hypertrophy. Another patient had an inconsistent apical holosystolic murmur. Two patients had alpha streptococcal endocarditis; neither was known to have pre-existing valvular disease. Fourteen patients had ECG criteria for left ventricular hypertrophy (LVH). Three patients were known to have associated aortic valve disease. The symptoms of IHSS may be nonspecific; asymptomatic patients with and without cardiac murmurs may be observed. Coexisting valvular disease, coronary artery disease, and bacterial endocarditis were documented. Patterns of myocardial infarction on ECG were not seen in these 27 patients.

Aged↗
PubMedDate not supplied

Renin-secreting tumor. Case report.

Renin-secreting tumor, though rare, should be considered in assessing severe hyperreninemic, hypertensive patients. We studied an 18-year-old girl with hypokalemic hyperreninemic hyperaldosteronism. No angiographic lesion could be detected. The plasma renin activity (PRA) of the right/left renal vein was 7.3. With a presumptive diagnosis of renin-secreting tumor (RST), the patient was operated on, and a cortical nodule was found on the right lower pole. Partial nephrectomy was followed by a rapid fall in PRA (half-life, 33-44 min) and normalization of blood pressure (BP). At 3 1/2 months postoperatively, the patient showed normotension, normokalemia, normal aldosterone, and slightly elevated PRA unresponsive to postural changes and furosemide treatment. Tumoral PRA secretion responded to postural stimulus, spironolactone use, and nitroprusside-induced hypotension. Neither the high aldosterone excretion nor hyperreninemia decreased after 3 days of DOCA; this agrees with a previously reported case suggesting the usefulness of this test in the diagnosis of RST.

Adolescent↗
PubMedDate not supplied

DOCA test for aldosteronism: its usefulness and implications.

Experience with the DOCA test (measurement of urinary excretion of aldosterone before and after 3 days of administration of 10 mg deoxycorticosterone acetate [DOCA] intramuscularly every 12 hours while on high sodium intake) is presented in 129 hypertensive patients to define its usefulness in discriminating between autonomous and nonautonomous production of aldosterone. All patients who did not have primary aldosteronism had a decrease in urinary excretion of aldosterone to values within the normal range, with a greater than 30% fall from control values. Patients with an aldosterone-producing adenoma had a 5.7% fall and those with idiopathic hyperaldosteronism had a 9.9% fall. Sodium retention was limited in these patients when compared with that in normal subjects. The least retention occurred in patients with an aldosterone-producing adenoma, whereas patients with low-renin essential hypertension retained more sodium than any other hypertensive group; the latter required greater sodium retention than those with normal-renin essential hypertension to produce a similar decrease in urinary aldosterone. Sodium retention correlated significantly with the percent fall in urinary aldosterone only in the low-renin essential hypertension group. Serum potassium levels fell in all groups. Changes in serum potassium levels and plasma renin concentration did not correlate with changes in urinary aldosterone excretion. The DOCA test is effect in discriminating between primary aldosteronism and other causes of hypertension. It also demonstrates that in hypertensive patients small changes in sodium retention reduce aldosterone excretion.

Adenoma↗
PubMedDate not supplied

Characterization of chick serum lipoproteins isolated by density gradient ultracentrifugation.

Serum lipoproteins from 12h fasted male chicks (15-day-old) were separated into 20 fractions by isopycnic density gradient ultracentrifugation. A new procedure was described by collecting the different fractions from the bottom of tube instead of by aspiration from the meniscus of each tube. Analyses of chemical composition of serum lipoproteins have permitted to reevaluate the density limits of major classes: VHDL, d greater than 1.132 g/ml; HDL, d 1.132-1.084 g/ml; LDL, d 1.084-1.038; IDL, d 1.038-1.022; and VLDL d less than 1.022. HDL fractions clearly predominated (approx. 77% of total lipoproteins) while IDL and VLDL were present at low percentage. LDL was the fraction richest in cholesterol; triacylglycerol content clearly increased from HDL to VLDL, while protein content decreased. All the chemical components of chick serum lipoproteins were accumulated in HDL, although triacylglycerol was relatively distributed in all the lipoprotein classes.

Animals↗