PubMed Health⌕ Search

Biomedical subjects

D Predescu

Publications and source records attributed to D Predescu.

At least 19 recordsLinked to original sources
PubMed1999

Platelet activating factor receptor (PAF-R) is found in a large endosomal compartment in human umbilical vein endothelial cells.

In previous studies, we have localized the platelet activating factor receptor (PAF-R) in situ on the surface of the endothelium in a number of microvascular beds without providing information on its intracellular location. In the present study, we used human umbilical vein cells (HUVECs) as a model to immunolocalize PAF-R by light and electron microscopic procedures. We raised two different polyclonal antibodies against synthetic peptides of the C- and N-terminal of PAF-R and used them for immunolocalization studies. By immunofluorescence, we found that the anti-C-terminal antibody (CPAF-R) stains an extensive intracellular tubular network. By electron microscopy, using a preembedding staining procedure, we detected PAF-R on the surface of the plasmalemma in a staining pattern similar to that described on microvascular endothelia in situ, but at a considerably lower density. Immunogold labeling of thin frozen sections revealed the presence of PAF-R on the plasmalemma, and especially in an extensive network of tubular-vesicular elements and vesicles associated with it. No detectable amounts of PAF-R were found in the endoplasmic reticulum (ER) or in Golgi cisternae. Double immunofluorescence labeling with antibodies for compartment marker proteins and PAF-R revealed that PAF-R localizes in an endosomal compartment. Confocal microscopy showed that PAF-R colocalizes in this compartment together with the transferrin receptor (Tf-R) and the thrombin receptor (TH-R), but it also showed that the colocalization was partial rather than complete. These findings suggest that the endosomal network is either discontinuous or, conversely, that the proteins in its membrane do not have a fully randomized distribution.

Cells, Cultured↗
PubMed1998

Transcytosis of alpha1-acidic glycoprotein in the continuous microvascular endothelium.

By using perfusions and bolus administration, coupled with postembedding immunocytochemical procedures, we have identified the structures involved in the transport of derivatized orosomucoid (alpha1-acidic glycoprotein) across the continuous microvascular endothelium of the murine myocardium. Our findings indicate that: (i) monomeric orosomucoid binds to the luminal surface of the endothelium; (ii) it is restricted to caveolae during its transport across the endothelium; (iii) it is detected in the perivascular spaces at early time points (by 1 min) and in larger quantities at later time points (>5 min) from the beginning of its perfusion or its intravascular administration; (iv) no orosomucoid molecules are found in the intercellular junctions or at the abluminal exits of interendothelial spaces; and (v) the vesicular transport of orosomucoid is strongly inhibited by N-ethylmaleimide (>80%). Because, by size and shape, the orosomucoid qualifies as a preferential probe for the postulated small pore system, our results are discussed in relation to the pore theory of capillary permeability.

Animals↗
PubMed1997

Immunoisolation and partial characterization of endothelial plasmalemmal vesicles (caveolae).

Plasmalemmal vesicles (PVs) or caveolae are plasma membrane invaginations and associated vesicles of regular size and shape found in most mammalian cell types. They are particularly numerous in the continuous endothelium of certain microvascular beds (e.g., heart, lung, and muscles) in which they have been identified as transcytotic vesicular carriers. Their chemistry and function have been extensively studied in the last years by various means, including several attempts to isolate them by cell fractionation from different cell types. The methods so far used rely on nonspecific physical parameters of the caveolae and their membrane (e.g., size-specific gravity and solubility in detergents) which do not rule out contamination from other membrane sources, especially the plasmalemma proper. We report here a different method for the isolation of PVs from plasmalemmal fragments obtained by a silica-coating procedure from the rat lung vasculature. The method includes sonication and flotation of a mixed vesicle fraction, as the first step, followed by specific immunoisolation of PVs on anticaveolin-coated magnetic microspheres, as the second step. The mixed vesicle fraction, is thereby resolved into a bound subfraction (B), which consists primarily of PVs or caveolae, and a nonbound subfraction (NB) enriched in vesicles derived from the plasmalemma proper. The results so far obtained indicate that some specific endothelial membrane proteins (e.g., thrombomodulin, functional thrombin receptor) are distributed about evenly between the B and NB subfractions, whereas others are restricted to the NB subfraction (e.g., angiotensin converting enzyme, podocalyxin). Glycoproteins distribute unevenly between the two subfractions and antigens involved in signal transduction [e.g., annexin II, protein kinase C alpha, the G alpha subunits of heterotrimeric G proteins (alpha s, alpha q, alpha i2, alpha i3), small GTP-binding proteins, endothelial nitric oxide synthase, and nonreceptor protein kinase c-src] are concentrated in the NB (plasmalemma proper-enriched) subfraction rather than in the caveolae of the B subfraction. Additional work should show whether discrepancies between our findings and those already recorded in the literature represent inadequate fractionation techniques or are accounted for by chemical differentiation of caveolae from one cell type to another.

Absorption↗
PubMed1996

The vascular distribution of the platelet-activating factor receptor.

Although the platelet-activating factor (PAF) is the most active inflammatory mediator known to date, little is known about its effects on the vascular endothelium and about the cellular and subcellular distribution of its receptor, already identified as a membrane protein of approximately 39 kDa. To better understand its functions we decided: i) to study PAF effects on a model microvascular bed (the rat cremaster), ii) to raise monoclonal antibodies against synthetic peptides reproducing short segments (14 and 16 amino acids) at the N and C terminal parts of PAF-receptor (PAF-R), iii) to determine the distribution of PAF-R on a number of microvascular beds. Topical application of the PAF on the cremaster led promptly to: i) opening of the venular and capillary endothelial junctions; ii) fenestration of the endothelium and iii) swelling, clustering and fusion of endothelial plasmalemmal vesicles. With the anti-N terminal antibody, we localized PAF-R by immunofluorescence on semithin frozen sections of lung, heart, diaphragm, kidney, and brain specimens. With the exception of brain, the signal was restricted primarily to the vascular endothelium. Using immunogold procedures, we localized the PAF-R in small clusters on endothelial surfaces and found it associated preferentially with the plasmalemma proper, rather than to any differentiated microdomain. A morphometric analysis revealed a greater signal density at the level of the venular endothelium than at the level of the endothelium of any other segment of the microvasculature. With the same antibody, we immunoprecipitated PAF-R from whole homogenates of the same tissues. The results obtained were in general agreement with the immunofluorescence tests.

Amino Acid Sequence↗
PubMed1995

[Familial abdominal fibromatosis].

Two cases of abdominal fibromatosis are followed-up in two brothers patients development, each of them having a peculiar development. First of them underwent operation for a huge abdominal tumor with a retroperitoneal origin and intraperitoneal development which needed a complex partial resection with first jejunal loop enterectomy. The other patient had first surgery for fibrosarcoma of nuchal area and after that he underwent an operation for superior digestive haemorrhagia as a result of antral gastric fibroid tumor with transverse colic and mezocolic extension, which needed gastro-colectomy. The patients father was followed up for tangible abdominal tumors, but he rejected the proposed coeliotomia. The two brothers patients had a good postoperative development. The examination of the charriotype showed anomalies of the short branch of the 21st and 22nd chromosome (which are still normal).

Abdomen↗
PubMed1994

Transcytosis in the continuous endothelium of the myocardial microvasculature is inhibited by N-ethylmaleimide.

In a murine heart perfusion system, we were able to "turn off" the transport of derivatized albumin [dinitrophenylated albumin (DNP-albumin)] from the perfusate to the tissue, by preperfusing the system with 1 mM N-ethylmaleimide (NEM) for 5 min at 37 degrees C, followed by a 5-min perfusion of DNP-albumin in the presence of NEM. Using a postembedding immunocytochemical procedure, we showed that (i) a 30-sec to 1-min treatment of heart vasculature with 1 mM NEM reduces the transendothelial transport of DNP-albumin and nearly stops it after 5 min, and (ii) DNP-albumin is detected exclusively in plasmalemmal vesicles (PVs) while in transit across endothelial cells. Perfusion with 10 mM dithiothreitol for 1 min before NEM prevents the inhibition of vesicular transport. To quantitate the NEM effect on vesicular transport inhibition, we developed an ELISA and a dot-blot assay for measuring DNP-albumin in supernatants of perfused whole-heart homogenates. The results obtained indicate that the treatment of the heart vasculature with 1 mM NEM decreases the vesicular transport of DNP-albumin by 78-80%. Since NEM is known to inhibit the fusion of different types of vesicular carriers with their target membranes in other cell types and in in vitro reconstituted cellular systems, by alkylating a NEM-sensitive factor, we assume that the same mechanism applies in our in situ system. The decrease of vesicular transport can be explained by NEM preventing the fusion of recycling vesicles with their targets--i.e., the abluminal and luminal domains of the plasmalemma. The results open to question previous interpretations from other laboratories according to which plasmalemmal vesicles are sessile, immobile structures.

Albumins↗
PubMed1993

Plasmalemmal vesicles represent the large pore system of continuous microvascular endothelium.

In the capillary physiology literature, molecules and particles larger than 10 nm are assumed to leave the plasma mostly through large pores located at the level of intercellular junctions in microvessels lined with a continuous endothelium. In morphological studies of similar microvessels, outgoing particles > 10 nm were detected in endothelial plasmalemmal vesicles not in intercellular junctions. Because the probes may not be found in transit through the junctions because they may be swept away by strong currents generated by Starling forces, we have examined a large number of junctions in arteriolar, capillary, and venular segments of bipolar vascular fields of mouse diaphragms collected after perfusion with large pore probes. The results presented in this study indicate that 1) the perfused probes accumulate in the luminal introits of the junctions as filtration residues that decrease in size and frequency from arterioles to venules, and 2) large pore probes move across the endothelium exclusively through plasmalemmal vesicles.

Animals↗
PubMed1988

Binding and transcytosis of glycoalbumin by the microvascular endothelium of the murine myocardium: evidence that glycoalbumin behaves as a bifunctional ligand.

The binding and transport of glycoalbumin (gA) by the endothelium of murine myocardial microvessels were studied by perfusing in situ 125I-gA or gA-gold complexes (gA-Au) and examining the specimens by radioassays and EM, respectively. After a 3-min perfusion, the uptake of radioiodinated gA is 2.2-fold higher than that of native albumin; it is partially (approximately 55%) competed by either albumin or D-glucose, and almost completely abolished by the concomitant administration of both competitors or by gA. D-mannose and D-galactose are not effective competitors. Unlike albumin-gold complexes that bind restrictively to plasmalemmal vesicles, gA-Au labels the plasma-lemma proper, plasmalemmal vesicles open on the lumen, and most coated pits. Competing albumin prevents gA-Au binding to the membrane of plasmalemmal vesicles, while glucose significantly reduces the ligand binding to plasmalemma proper. Competition with albumin and glucose gives additive effects. Transcytosis of gA-Au, already detected at 3 min, becomes substantial by 30 min. No tracer exit via intercellular junctions was detected. gA-Au progressively accumulates in multivesicular bodies. The results of the binding and competition experiments indicate that the gA behaves as a bifunctional ligand which is recognized by two distinct binding sites: one, located on the plasma membrane, binds as a lectin the glucose residues of gA; whereas the other, confined to plasmalemmal vesicles, recognizes presumably specific domains of the albumin molecule.

Animals↗
PubMedDate not supplied

Correlation between left ventricular diastolic function and exercise testing in patients with old myocardial infarction.

There is no correlation between left ventricular (LV) systolic function and effort capacity of the patients with acute or old myocardial infarction (MI). On the other hand, some recent studies suggest such a relationship for LV diastolic function. Twenty-five patients with old MI were submitted to a maximal symptoms limited exercise testing (ET) and to an echo Doppler examination; functional aerobic impairment (FAI), myocardial aerobic impairment (MAI), maximal exercise capacity (METs NYHA class), isovolumic relaxation time (IVRT), E and A wave velocity, E/A rate being calculated. There is a negative significant correlation between MAI and E velocity (r = -0.68), but not between MAI and A velocity or IVRT. The data sustained the correlation between LV diastolic dysfunction and myocardial ischemia, but not with effort capacity of the patients, the last one being determined mainly by other factors. The LV diastolic function indices were modified in anterior but not in inferior MI, in relation with the amount of myocardial necrosis. It is concluded that, like LV systolic function, LV diastolic function does not correlate with the effort capacity of the patients with MI, but it represents a good predictor of the severity of myocardial ischemia mainly in anterior MI.

Diastole↗
PubMedDate not supplied

Effect of exercise training upon left ventricular systolic performance and effort capacity in patients with old myocardial infarction.

Recent studies suggested an improving of left ventricular (LV) systolic function during exercise training in patients with old myocardial infarction. Twenty patients with old myocardial infarction (3-6 weeks) were included in an exercise training programme (mainly cycloergometer) for 2 to 8 weeks. Before and after the exercise training programme, the effort capacity and LV systolic function were determined through exercise testing on cycloergometer and echocardiography. The peak effort raised from 4.39 to 5.27 METs (p < 0.05) and the difference DAF-DAM was reduced from 25% to 12% (p < 0.05). The double product (DP) at peak effort raised nonsignificantly (4.91%, p > > 0.05), but at submaximal effort levels DP decreased significantly on each effort step (12.16%, p < < 0.05). In turn, LV systolic function calculated parameters were practically the same before and after the exercise training programme. (EDD 54.3 vs 5.3 mm, ESD 39.3 vs 38 mm, EDV 160 vs 169 ml, ESV 60.6 vs 54.8 ml, EF 54.1% vs 57.8%, SF 27.6% vs 31.2%). It is concluded that exercise training raised the effort capacity in patients with old myocardial infarction, mainly through peripheral mechanisms, LV systolic function being unchanged. It is also important that exercise training have not any detrimental effect upon LV systolic function and consequently exercise training programmes can be applied and can be useful also in patients with old myocardial infarction and impaired LV systolic function.

Adult↗
PubMedDate not supplied

Ischemic preconditioning during successive exercise testing.

It was suggested recently that ischemic preconditioning can occur in clinical practice. We investigated this hypothesis in 26 patients with old myocardial infarction (MI) or stable angina pectoris, subjected to two successive exercise testings at 1 hour interval. The ST depression was significantly lesser during the second exercise testing (1.83 +/- 0.12 mm, vs 1.02 +/- 0.14 mm p < 0.01) at the same double product (DP) (24.877 +/- 1206 vs 24.711 +/- 1152 p > 0.05) and peak effort (76.92 +/- 6.63 w vs 75.96 +/- 6.27 w p > 0.05). The improvement was attributed to ischemic preconditioning.

Adult↗
PubMedDate not supplied

[Problems and difficulties in patients with esophageal reconstruction].

The esophageal reconstruction, independent of the manner and indication represents a major challenge for any surgical team. The goal of the present study is the retrospective analysis of cases together with the technical possibilities of surgical approach, viewed through the diagnostical and therapeutical point of view. We analysed retrospectively 154 patients (140 post-caustical stenosis and 14 neoplasms) who have took benefit of reconstructive esophageal surgery, operated in the last 21 years (1981-2001) in the clinic of surgery, of "Saint Mary" Hospital. Although the esophageal substitution has multiple indications (malignancy, benign stenosis, iatrogenic fistulas, reflux disease with peptic stenosis, etc.), in our clinic the technique was performed for neoplasic lesions and post-caustical corrosive stenosis. In the first period of the study (1981-1990) the most utilised method of surgical approach was the gastric tubulisation after the Gavriliu I or II procedures; in a second period (1990-2001) it is obvious that the tendency was to use the colon or the whole stomach as principal visceras for reconstructions. About the immediate results, the majority of post-operative complications where minors, the most frequent problem being of pleuro-pulmonary nature. We have registered two deceases of patients with corrosive pathology and no post-operative mortality in the first 30 days in neoplasic patients. We evaluated the post-operative functional results using an evaluation score. The anastomotic functionality was good or excellent in most cases (80%), especially in non-malignant reconstructions. For the selection of the most suitable reconstructive procedure, a variety of factors must be explored and evaluated. After a long period in which the use of the colon, in different technical manners, represented the "golden standard" in esophageal reconstruction, we have observed a reevaluation of this attitude and also the more and more frequent utilisation of the whole stomach as esophageal substitute, especially in malignancy.

Adolescent↗
PubMedDate not supplied

Dipyridamole-exercise association in the diagnosis of ischemic heart disease.

Dipyridamole-exercise ECG test (DET) was found to present a greater sensitivity than exercise or dipyridamole ECG test alone in detecting ischemic heart disease (IHD). A group of 39 patients with probable IHD and negative exercise test was investigated by i.v. dipyridamole administration. Eight subjects presented significant ECG changes. The remaining 31 subjects were submitted to a new exercise test which became positive in 7 subjects (23%). The percentage increases to 38% by taking into account the positive dipyridamole test. The authors concluded that DET substantially improve the diagnosis of myocardial ischemia in subjects with probable IHD and negative exercise test.

Coronary Disease↗
PubMedDate not supplied

A comparative study of the renin-like activity in the heart and vascular system under various experimental conditions.

Renin-like activity in the heart and aorta of rats being slightly modified by binephrectomy, its variations in DOCA hypertension and infarcted ventricular muscle were studied. The daily i.p. administration of DOCA 12 mg/kg body weight for 35 days in male adult rats resulted in a significant decrease of renin activity in plasma and tissues of the heart, aorta, hypothalamus and hypophysis. In contrast to renin-like activity, cathepsin D measured in the same animals increased in all organs, except for the plasma. Similar changes of renin-like activity were observed in salt-loaded animals with 1.7% sodium chloride solution ad libitum for 35 days. In the infarcted myocardial ventricular muscle of the rats and rabbits, the tissue isorenin showed a tendency to decrease, associated with a significant increase in cathepsin D activity. Like in aorta, isorenin seems to be a different enzymatic entity of cathepsin D in the myocardial tissue. The measurement of isorenin content of the vascular endothelium and cardiac muscle fibers seems to reveal much higher amounts in the coronary vascular endothelium than in the myocardial fibres. The activation of the enzymatic angiotensin forming mechanisms in the coronary vascular bed could be one of the risk factors in myocardial infarction.

Animals↗
PubMedDate not supplied

Exercise testing in patients with valvular diseases.

Sixty-eight patients with valvular diseases (VD) were subjected to maximal, symptoms limited, exercise testing (ET) using a cycloergometer. The exercise was limited in 82% of the valvular patients by dyspnea attributed to pulmonary capillary pressure rising, even if in the 20 patients with mitral stenosis the relation between the effort intensity and mitral valve area (MVA) (echo) was absent (r = 0.26). Myocardial aerobic impairment (MAI) was absent in 17%, mild in 41%, moderate in 39% and severe in 3% of the patients with VD. It was considered overestimated, the effort being stopped, in 2/3 of the patients, before a heart rate of 85% of maximal heart rate (MxHR) was reached. This suggests that the patients with VD unlike coronary patients, still have a reserve of increasing MVO2 when exercise is stopped. Even in the above condition, the average difference between functional aerobic impairment (FAI) and MAI was 6% for NYHA I, 10.6% for NYHA II and 17% for NYHA III showing a physical deterioration in patients above the limit imposed by the valvular disease itself. ST segment depression of 1 mm or more at 0.08 s after J point was registered in 30% of the patients. Due to the insufficient rise of the heart rate (HR) in the majority (2/3) of the patients with VD, these data probably underestimate the myocardial ischemia. Consequently other stress testings whose main action is not the increase of HR and MVO2 i.e., dypiridamole and adenosine, are preferred in the investigation of myocardial ischemia in the patients with VD.

Aortic Valve↗