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Biomedical subjects

S Masdeu

Publications and source records attributed to S Masdeu.

At least 37 records · Page 2Linked to original sources
PubMed1979

[Bile acids. I. Nature, physiology, and functions (author's transl)].

Bile acids play a fundamental role in the degradation and absorption of intestinal lipids. The primary ones are cholic acid and chenodeoxycholic acid which are synthesized from cholesterol in the liver and conjugate with taurine and glycine amino acids. The secondary bile acids are derived from the primary ones by the enzyme action of intestinal bacteria through a process of deconjugation and dehydroxylation. Their detergent property is based on the molecular configuration of these compounds, which present a hydrophilic and a hydrotion of these compounds, which present a hydrophilic and a hydrophobic surface. The different enzymes in the liver cells that intervene in the process of synthesis of bile acids are now known. A basic element in their physiology is the enterohepatic circulation, enabling the organism to take maximum advantage of these compounds. The dynamics of the cycle are maintained and regulated by the system of uptake and secretion of the cells, cholecystokinin, intestinal peristalsis, active transport across the ileal membrane, and by portal venous flow. Much of our knowledge about the biogenesis and functions of the bile acids has been acquired quite recently. Research over the past three decades has contributed to a great advance in our understanding of their physiology.

Bile Acids and Salts↗
PubMed1979

In vivo and in vitro relationship between lipoprotein-X and bile salts in cholestasis.

Bile salts have been shown to act on lipoprotein-X (LP-X) in vitro to induce a false-negative electrophoretic test. The aim of the present study was to investigate the relationship between serum LP-X and serum bile acids in patients with cholestasis. The in vitro concentration of bile salts required to induce a negative or reduced concentration of LP-X was also studied. There was no relationship, either positive or negative, between serum LP-X and bile acids in 34 patients with cholestasis. Serum was incubated with various saline solutions of taurocholic, lithocholic, deoxycholic and glycocholic acids. The concentration of LP-X decreased only after the final concentrations of bile salts were over 2,000 mumole/1. This is more than five times the concentration of serum bile salts usually found in patients with cholestasis. It is concluded that the negative LP-X test in some patients with cholestases must be explained by some other mechanisms than bile salts.

Bile Acids and Salts↗
PubMed1977

The clearance of lipoprotein X in vitro, and effect of phospholipase A on serum lipoprotein X.

The in vitro effect of post-heparin and post-heparin plus post-protamine normal serum on serum lipoprotein X (LP-X) is described. Serum LP-X is cleared after incubation with post-heparin normal serum, and serum LP-X remain unmodified when it is incubated with post-heparin plus post-protamine normal serum. The action of phospholipase A from snake venom on serum LP-X is also studied. A very small quantity of phospholipase is necessary to degrade LP-X and to transform lecithin into lysolecithin. It is concluded that phospholipase seems to be the enzyme that most likely induces the LP-X changes after heparin administration.

Adult↗
PubMed1977

Evidence of agar gel electrophoresis changes of lipoprotein-X after phospholipase A and deoxycholic acid.

The effect of phospholipase A from snake venom and deoxycholic acid on lipoprotein-X (LP-X) recovered from the cathode side of a previous agar gel electrophoresis is described. Adding phospholipase A and deoxycholic acid to the removed cathodal fraction is followed by a marked migration to the anode side on a second electrophoresis procedure. This seems to confirm that phospholipase A and bile salts on LP-X particles modifying their agar gel electrophoretic migration characteristics.

Cholestasis↗
PubMed1977

Liver tissue lecithin: cholesterol acyltransferase activity in patients with liver disease.

Lecithin: Cholesterol acyltransferase (LCAT) activity was measured in serum and liver tissue from patients with parenchymal liver disease. Serum LCAT activity was within normal limits and it was probably related to the absence of clinical and laboratory evidence of a decompensated liver function. Liver tissue LCAT activity is about tenfold lower than that in serum. The relative proportion of cholesterol esters in liver tissue was much higher that could be expected according the low tissue LCAT activity. This findings suggest that LCAT is a "plasma specific" enzyme and that cholesterol esters in parenchyma may be considered as a storage form of cholesterol esterified in plasma pool.

Acyltransferases↗
PubMed1976

Effect of heparin on lecithin: cholesterol acyltransferase and lipids in cholestasis.

The effect of heparin on the proportion of cholesterol esters, lecithin/lysolecithin ratio, and lecithin: cholesterol acyltransferase (LCAT) activity was studied in twelve patients with cholestasis. A good correlation was observed between a decreased LCAT activity and the proportion of cholesterol esters, and no consistent variation was noted after heparin. The lecithin/lysolecithin ratio was increased in 7 patients and became normal after heparin in 6 cases. The clearance of lipoprotein-X after heparin seems to be not related to LCAT activity. These results demonstrate that heparin does not modify the LCAT activity, and suggest that heparin induces an increase of phospholipase activity in some patients with cholestasis.

Acyltransferases↗
PubMed1976

Action of heparin on lecithin:cholesterol acyltransferase activity in normal subjects.

The triglyceride decrease and free fatty acid increase by lipoproteinlipase post-heparin effect does not modify the Lecithin:Cholesterol Acyltransferase activity in vitro, using homologous substrate, in normal subjects. These findings agree with the unmodified proportion of esterified cholesterol and relative proportion of phospholipids on thin layer chromatographic fractioning after heparin. The conclusion is reached that heparin has no action on Lecithin:Cholesterol Acyltransferase activity in normal subjects.

Acyltransferases↗
PubMed1976

[Determination of lecithin: cholesterol acyltransferase activity by a radioisotopic assay (author's transl)].

A method for determining Lecithin: Cholesterol Acyltransferase (LCAT) activity is presented. Trace amounts of labelled cholesterol are added to innactivated homologous substrate from a pool of normal serum. LCAT activity is determined measuring the cholesterol esterification, and is expressed as micrograms of cholesterol esters formed per milliliter plasma per hour. LCAT time-course, reproducibility, activity after serum storage at 4 degrees C, and normal values from 20 healthy subjects are studied.

Acyltransferases↗
PubMed1975

The effect of heparin on serum lipoprotein-X.

Serum lipoprotein-X was investigated in 12 patients with cholestasis in basal conditions and 20 minutes after intravenous heparin. In all cases, lipoprotein-X was positive in the first sample and became negative after heparin. A decrease in triglycerides was observed in all patients after heparin with an increase in free fatty acids and mobilization of prebetalipoproteins, and a transformation of lecithin into lysoleithin in 4 cases after heparin. These facts suggest that heparin plays an important role in the mobilization of serum lipoprotein-X.

Adult↗