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Biomedical subjects

H Lafont

Publications and source records attributed to H Lafont.

At least 145 records · Page 8Linked to original sources
PubMed1980

Effect of bile lipids on the adsorption and activity of pancreatic lipase on triacylglycerol emulsions.

Emulsions of natural triacylglycerols obtained with different shear forces were used to study lipase adsorption and lipolysis. The influence of the bile lipoprotein complex on these two processes was determined. Optimal lipase activity was observed to occur with a given phospholipid : triacylglycerol ratio. This ratio depended on the degree of triacylglycerol emulsification and was accompanied by maximal adsorption of the bile lipoprotein complex. These results support our previous model for pancreatic lipolysis under physiological conditions, according to which colipase controls lipase binding to the bile lipoprotein complex and the resulting association directs enzyme adsorption to the acylglycerol particle (Lairon, D., Nalbone, G., Lafont, H., Léonardi, J., Domingo, N., Hauton, J.C. and Verger, R. (1978) Biochemistry 17, 5263--5269).

Adsorption↗
PubMed1979

The apoprotein fraction of the bile lipoprotein complex: isolation, partial characterization and phospholipid binding properties.

A bile apoprotein fraction (Apo BLC) was isolated by preparative isoelectric focusing (I.E.F.) from the detergent-free form of the bile lipoprotein complex (BLC). Analytical I.E.F. of Apo BLC yields a characteristic and reproducible pattern of two narrow acidic bands (pI 4,8-5,0). This apoprotein presents a strong tendency to undergo self-aggregation in aqueous buffer. A low molecular weight constituent of Apo BLC has been isolated after gel filtration, its mean Mw is estimated by SDS-PAGE at 7,500 daltons. The binding capacity of Apo BLC for phospholipids was investigated on dimyristoylphosphatidylcholine liposomes by gel filtration and zone electrophoresis. The resulting structures, larger than the original single-shelled vesicles, acquire and anodic electrophoretic mobility. Apo BLC has a weaker affinity for lysophosphatidylcholines: these phospholipids decrease the degree of aggregation of the apoprotein. These studies contribute additional data concerning the high affinity of Apo BLC for phosphatidylcholines, which are the major phospholipid constituents of bile. The discussion deals with the fact that association of Apo BLC with bile phosphatidylcholines may present some implications in the pathogeny of LpX and in the process of intestinal fat absorption.

Apolipoproteins↗
PubMed1979

[Dynamic study of the coronary vascular bed by selective coronary scanning using hyperaemia].

Advantage may be taken of the hyperaemic response to the iodine contained in the contrast medium injected during coronary angiography to assess the functional value of the coronary tree using radioactive microspheres. This series comprises 73 selective coronary scans performed in the resting state (113 m In marked microspheres) and during the hyperaemic phase (99 m TC marked microspheres) in 70 patients. A positive hyperaemic response distal to severe truncular stenosis indicates a good distal arteriolar bed and collateral circulation for aorto-coronary bypass grafting. After aorto-coronary bypass (23 cases), the hyperaemic response gives an indication of the functional value of the revascularised myocardium. In 71% cases, the results correlate well with the measurement of the peroperative blood flow through the graft. It is usually positive when the bypass graft is implanted with good distal arterial run off.

Adult↗
PubMed1978

Possible roles of bile lipids and colipase in lipase adsorption.

The adsorption isotherms of bile salts, phospholipids, and cholesterol were determined with siliconized glass beads. It was observed that the molar fractions of cholesterol, phospholipid, and bile polypeptide fractions increased simultaneously and considerably on the surface of the beads in comparison to the corresponding fractions found in bile. The composition of the adsorbed film is approximately 1 cholesterol: 2 phospholipid: 3 bile salt molecules. The performed complex of lipase, colipase, and bile lipids behaves as an entity which determines lipase adsorption. The modification of the interface quality of a lipid substrate by a detergent is not perse the reason for the lack of lipase adsorption. A model is proposed according to which lipolysis under physiological conditions would occur in two steps requiring two cofactors. Colipase would be necessary for the formation of the lipase-bile lipoprotein complex, and bile lipids would be required to direct the adsorption of this lipolytic entity toward the emulsified substrate.

Adsorption↗
PubMed1978

Inhibition of lipase adsorption at interfaces. Role of bile salt micelles and colipase.

The effects of bile salts and colipase on the adsorption of lipase at an interface were studied by hydrophobic affinity chromatography on phenyl- and octyl-Sepharose. In the absence of bile salts, lipase or colipase binds separately to the gel. This is unchanged in the presence of adsorbed bile salts, when one bile salt molecule is associated per hydrophobic ligand. The same data are obtained in the presence of monomeric bile salt solutions. In contrast, lipase adsorption is totally prevented in a micellar bile salt solution. These results favor the idea that the formation of a lipase-bile salt complex in solution is responsible for the lack of interfacial lipase adsorption.

Adsorption↗
PubMed1978

[Coronary angiography in the preoperative exploration of non-ischemic acquired valve diseases].

One hundred and fifty-nine patients with aortic valve disease (86 cases), mitral valve disease (58 cases) or mitral and aortic disease (15 cases) underwent a pre-operative haemodynamic study, including coronary arteriography either as a routine (age greater than 50 years) or because of chest pains. Coronary arteriography is easy to do during left heart catheterisation and nowadays carries minimal risk. In the cases of chest pains, it showed stenotic lesions of the coronary vessels in 22% of patients with aortic valve disease and in 35% of those with mitral disease. In the absence of angina, coronary arteriography showed no evidence of coronary artery disease in the cases of mitral regurgitation and of aortic valve disease. In contrast, it showed stenotic lesions in three cases of mitral stenosis. In the whole of the series, coronary artery disease proved a contra-indication to surgery in three cases, and was an indication for aorta-coronary by-pass grafting, in addition to valve surgery, in seven other cases. In the absence of angina, coronary arteriography has only a slight influence on the decision to operate. It does however give additional security, which justifies its routine use in patients over 50 years of age, particularly those with mitral valve disease.

Adult↗
PubMed1978

[Restricted myocardial infarction. Coronary angiographic and ventriculographic findings. Comparison with acute coronary insufficiency and transmural infarction].

The findings at coronary arteriography and ventricular angiography in 52 patients with a restricted myocardial infarct were compared with those of 106 patients with acute coronary insufficiency and 100 with transmural infarcts. Certain features place restricted myocardial infarction in an intermediate category when compared with the two other syndromes. The percentage of coronary occlusions was significantly higher in transmural infarction (23.5%) and in restricted infarction (16.6%) than in acute coronary insufficiency 6.8%). Study of the vessel beyond a tight stenosis (greater than or equal to 75% was particularly effective in clearly separating the three groups. As a result, 63% of patients with coronary insufficiency, 40% of these with restricted infarcts, and only 23% of patients with a transmural infarct could be referred for surgery. Ventricular angiography showed a close relationship between restricted infarction and acute coronary insufficiency because ventricular function appeared normal or subnormal (localised hypokinesia) in 69% and 81% of cases respectively, compared with 4% of cases of transmural infarction. Restricted myocardial infarction appears to resemble coronary insufficiency, but shows elevation of enzymes and often more marked disease of distal vessels.

Acute Disease↗
PubMed1977

A comparative in vivo study of intestinal absorption of biliary phosphatidylcholines and micellar phosphatidylcholines in the rat.

An in vivo study was performed using rats with the purpose of comparing the absorption of native biliary and purified phosphatidylcholines. The latter were purified from bile and solubilized in the form of mixed micelles of bile salts-phosphatidylcholines-cholesterol. The animals all bore bile duct diversions, and were divided into two groups: one had a normal pancreatic secretion while in the other group the pancreatic duct was ligated. Animals with normal pancreatic secretion showed comparable rates of absorption of micellar and biliary phosphatidylcholines. In the absence of normal pancreatic secretion, the rate of absorption of biliary phosphatidylcholines was unchanged, whereas that of micellar phosphatidylcholines markedly decreased. The results are consistent with the concept that some biliary phosphatidylcholines are absorbed independently of pancreatic secretion in an unhydrolyzed form.

Animals↗
PubMed1977

Zone electrophoresis study of the bile lipoprotein complex.

Sucrose gradient column electrophoresis was performed with human hepatic and gallbladder bile. It is shown that bile phosphatidylcholines exhibit a more rapid anodic mobility than do bile salts and serum albumin. This high mobility of bile phosphatidylcholines is not due to the negatively charged lipids which are present in bile, i.e. bile salts or free fatty acids. It is demonstrated that phosphatidylcholines are associated with anionic polypeptides. Electrophoresis of reassociations between these purified polypeptides and dilaurylphosphatidylcholine showed that these anionic polypeptides are primarily responsible for the high anodic mobility of the bile lipoprotein complex. This work describes a procedure for the purification of the bile lipoprotein complex which can be useful for the study of other kinds of lipid-polypeptide associations.

Amino Acids↗
PubMed1977

[Coronary arteriography in the threatened infarction syndrome].

Although greater than in patients with stabilised coronary insufficiency, the risks of carrying out coronary arteriography during the period of a threatened infarction are still modest in the hands of an experienced team. In a series of 66 such investigations under these conditions over an 18 month period, there were no deaths as immediate sequelae. Three myocardial infarctions occurred, one of which was probably encouraged by ceasing the propranolol prior to arteriography. Analysis of the results confirms the frequency of lesions affecting all three trunks (47% of cases), the anterior descending branch being the most commonly affected. A collateral circulation was established in 23% of cases. Ventriculography was normal in one third of cases. The mean value for the ventricular ejection fraction was 0.57 over the entire series. In 58% of cases, all the arteriographic and ventriculographic criteria of operability were satisfied. It therefore appears that coronary arteriography is justifiable during the period of threatened infarction; it may be undertaken at an early stage if the angina does not respond to medical treatment. It is always best to carry it out several days after cessation of the pain where possible. The investigation may lead to urgent surgical intervention.

Adult↗
PubMed1977

[The end-diastolic pressure-volume relationship of the left ventricle. Significance for the indices of compliance and diastolic rigidity of the ventricle].

In order to evaluate the importance of the indices of ventricular rigidity and compliance (k=dP/dV.P and dV/dP), three groups of patients were studied and compared. A simplified method of calculating the diastolic compliance made use of the values of end-diastolic volume (EDV) measured by cineangiography, and of end-diastolic pressure (EDP), using the assumption that the relationship P-V is an exponential one arising from the ordinate: 0.43 mmHg. The correlation between EDP and EDV, which was positive in 19 coronary artery patients, was in fact negative in 11 patients with obstructive cardiomyopathy (OCM), and insignificant in 12 control patients. There were multiple correlations between k, EDPs and EDVs in 11 OCMs, and none in the two other groups. The ratio dV/dP decreased in end-diastole both in the OCM group and in the coronary group, and did not reflect the difference in pathology between these two groups. On the other hand k was increased in the patients with OCM, normal in the coronary patients, and represented in the former a primary modification in the relationship P-V and a primary increase in diastolic rigidity.

Cardiac Output↗