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Biomedical subjects

M Pan

Publications and source records attributed to M Pan.

At least 37 records · Page 2Linked to original sources
PubMed1999

Immediate and follow-up findings after stent treatment for severe coarctation of aorta.

Experimental studies have shown that stents implanted at the aorta become incorporated within the aortic wall and can be further expanded in growing animals. Few clinical studies have shown that the stent repair of severe coarctation of aorta provides excellent initial results, and little is known on the follow-up of these patients. We assessed the immediate and follow-up results obtained in a series of 48 patients (mean age 14+/-12 years) with severe coarctation of the aorta who were treated by Palmaz stent implantation; 30 of them (63%) underwent angiographic follow-up studies at a mean of 25+/-11 months after treatment. Quantitative serial analysis of the aortogram (baseline, after treatment, and at follow-up) was performed. Significant relief (mean residual gradient 3+/-4 mm Hg) was always obtained after stent implantation. The isthmus, when hypoplastic (60%), was always expanded with the stent. One associated aneurysm became occluded after the implant. Complications included aortic disruption, stent migration, and decreased or absent femoral pulses. At angiographic follow-up, the stent remained always in place, without recoil. In 22 patients (73%), there were no detectable neointimal proliferation at late angiogram; however, 8 patients (27%) had some degree of intimal thickening (1 to 5 mm), causing mild restenosis in 3 patients treated at early age, and nonsignificant lumen reduction in 5. The serial aortogram analysis revealed a minor but significant increase in nonstented aortic diameters that seemed related to the normal growth of children. No need for stent reexpansion was observed at 2-year follow-up (mean). Two patients (7%) developed late small aneurysm formation at the stented wall; both were occluded by the insertion of coils through the stent orifices. We conclude that stent treatment for severe coarctation of aorta provides excellent immediate and long-term results in young adults and children. However, at early age, restenosis by intimal growth may develop.

Adolescent↗
PubMed1999

[Coronary angioplasty: always a stent in arteries larger than 2.5 mm? The arguments pro].

Coronary stenting has provided better results than balloon angioplasty in terms of primary success and restenosis in previous randomized studies. These studies only included short coronary lesions located in vessels larger than 3 mm. Thus, these results can not be applied to complex lesions or those located in small vessels. In the present article we summarize our points of view regarding the current indications of coronary stenting in these types of lesions, where the use of this device may be still controversial. In all these situations the results of the stent seem to be better to those previously reported with balloon angioplasty. However, there is a percentage of patients treated by balloon angioplasty in whom a good immediate and long-term result can be obtained. The identification of patients with optimal result after balloon angioplasty need a postprocedure study of coronary flow reserve. The comparison of optimal balloon angioplasty (by angiographic and coronary flow reserve criteria) and stent, is the main objective of 2 studies that are currently under process. We will have to wait the results of these clinical trials to answer to the question if the implant of stents in all kind of lesions located in vessel larger than 2.5 mm is of proper use. Our current opinion is that coronary stenting is a safe and fast method of coronary transcatheter therapy in many types of coronary lesions and it may be considered the more efficient technique of percutaneous revascularization.

Angioplasty, Balloon, Coronary↗
PubMed1998

Neurotrophin receptor expression is induced in a subpopulation of trigeminal neurons that label by retrograde transport of NGF or fluoro-gold following tooth injury.

Tissue responses to injury are regulated by neurotrophins and neurotrophin receptor levels and can involve both retrograde and paracrine/autocrine trophic signaling. To determine how neurotrophins may contribute to the injury response, the timing and the extent of the up-regulation of neurotrophins and their receptors was examined in a model system which is particularly well suited for the analysis of trophic signaling pathways in response to injury. Injury to the occlusal surfaces of rat molar cusps induces a localized increase in nerve growth factor (NGF) expression in the dental pulp within 4-6 h. Radiolabeled NGF was transported in a receptor-mediated fashion from the teeth to a subset of neurons in the trigeminal ganglion within 15 h, indicating that these neurons possess NGF receptors (trk A and/or p75NTR). To test for NGF responses in the tooth sensory afferent neurons, levels of expression of neurotrophins and their receptors were examined by in situ hybridization in the trigeminal ganglion at 0, 4, 12, 20, 28 and 52 h post-injury. Within the maxillary division of the trigeminal ganglion, trk A expression was elevated at 4 h post-injury, with a maximum increase (2-fold) after 52 h. p75NTR was increased by 28 h post-injury and was increased 1.35-fold by 52 h. BDNF mRNA was increased 12 h after injury (1.8-fold), and 2.5-3-fold at 52 h post-injury. The trk B expression was increased only late after injury (28 and 52 h). To determine the receptor/neurotrophin phenotype of trigeminal neurons with projections to the molar teeth, these neurons were double-labeled with the retrograde tracer fluoro-gold and probes for either BDNF or trk B. The results show that tooth-innervating trigeminal neurons express BDNF, but not trk B. The timing of mRNA expression after injury and the phenotype of identified trigeminal neurons suggests a complex signaling cascade in which NGF at the injury site regulates NGF receptor expression at the levels of the cell body as well as increases in BDNF expression. Upregulated BDNF may act in a paracrine fashion on neighboring trigeminal cells expressing trk B. This signaling cascade may be a common feature of the response to mild peripheral inflammatory injuries within nociceptive pathways.

Animals↗
PubMed1998

The tetraspan protein CD82 is a resident of MHC class II compartments where it associates with HLA-DR, -DM, and -DO molecules.

In specialized APCs, MHC class II molecules are synthesized in the endoplasmic reticulum and transported through the Golgi apparatus to organelles of the endocytic pathway collectively called MHC class II compartments (MIICs). There, the class II-associated invariant chain is degraded, and peptides derived from internalized Ag bind to empty class II in a reaction that is facilitated by the class II-like molecule HLA-DM. An mAb raised to highly purified, immunoisolated MIICs from human B lymphoblastoid cells recognized CD82, a member of the tetraspan family of integral membrane proteins. Subcellular fractionation, immunofluorescence microscopy, and immunoelectron microscopy showed that CD82 is highly enriched in MIICs, particularly in their internal membranes. Coprecipitation analysis showed that CD82 associates in MIICs with class II, DM, and HLA-DO (an inhibitor of peptide loading that binds DM). Similar experiments showed CD63, another tetraspan protein found in MIICs, also associates with these molecules in the compartment and that CD82 and CD63 associate with each other. Preclearing experiments demonstrated that both CD82 and CD63 form complexes with DM-associated class II and DM-associated DO. The ability of CD82 and CD63 to form complexes with class II, DM, and DO in MIICs suggests that the tetraspan proteins may play an important role in the late stages of MHC class II maturation.

Animals↗
PubMed1998

Intracellular formation and cell surface expression of a complex of an intact lysosomal protein and MHC class II molecules.

The generation of invariant chain-free MHC class II molecules and their association with endocytically generated peptides are thought to occur in specialized lysosome-like compartments called MIICs (MHC class II compartments). A number of in vitro studies have shown that large denatured proteins can bind to class II molecules, and that class II association can protect the bound segment of protein from proteolytic degradation. In this work, we present what we believe is the first example of an intact endogenous protein (IP30) binding in an allele-dependent fashion to class II molecules in vivo. IP30 is an IFN-gamma-inducible 35-kDa glycoprotein that localizes in MIICs. In this study, we show that intact IP30 binds to certain HLA-DR alleles via an N-terminal prosequence. The association takes place in the endocytic pathway following removal of invariant chain from class II molecules and before their cell surface expression. We also show that DR-IP30 complexes are SDS stable. The potential precursor-product relationship between DR-IP30 complexes and the DR-peptide complex is discussed.

Alleles↗
PubMed1998

[Autologous endothelial cell transplantation in meacacos].

OBJECTIVE: To lay a theoretical foundation for the clinical application of autologous endothelial cell transplantation. METHODS: Macaco endothelial cells derived from superficial veins were cultivated in vitro for 13.89 +/- 1.36 days. The multiplied cells were lined in vitro onto the luminal surface of expanded polytetrafluoroethylene (ePTFE) grafts precoated with fibrin glue and fibronectin, then cultivated further for 9 days. 15 macacos were divided randomly into two groups. The common iliac arteries of the exper mental animals (n = 10) were replaced with endothelialized grafts, those of control (n = 5) with untreated ones. RESULTS: The amount of endothelial cells increased for 147.93 +/- 88.68 folds. All the cells were diploid cells with a purity of 99%. The content of both 6-keto-PGF1a and vWF in the supernatant of primary and subcultured passages didn't have significant difference. Two hours and 9 days after cell seeding, the luminal surface of grafts were covered completely by a prominent, spindle-like endothelial monolayer underneath an even fibrin glue matrix could be seen. Nine days after seeding, the dense condensation of cytoskeleton on the luminal and basal side of cells increased apparently. Four weeks after grafts implantation 8/10 of experimental grafts, with a thickness of intima 80 +/- 12 microns, were patent; while the 5 control grafts were occluded. CONCLUSION: The endothelial cell transplantation could effectively increase the patency rate of synthetic blood vessel prosthesis.

Animals↗
PubMed1997

In-laboratory removal of femoral sheath following protamine administration in patients having intracoronary stent implantation.

Two hundred twenty-eight patients with successful coronary stent implantation were randomized either to protamine administration and femoral sheath removal (group I, n = 117) or no heparin neutralization and delayed sheath removal (group II, n = 111). The hospital stay after treatment was shorter in patients receiving protamine; therefore, protamine use for neutralizing circulating heparin may be safely administered immediately after stent implantation.

Anticoagulants↗
PubMed1997

Identification of nonprotein amino acids from cycad seeds as N-ethoxycarbonyl ethyl ester derivatives by positive chemical-ionization gas chromatography-mass spectrometry.

Nonprotein amino acids from nine species of cycad seeds were analyzed as N-ethoxycarbonyl ethyl ester (ECEE) derivatives by positive chemical-ionization gas chromatography-mass spectrometry. Based on the retention times and mass spectrometry analyses, 12 nonprotein amino acids were identified in these seeds. In addition to the excitatory and putative neurotoxin beta-N-methylamino-L-alanine (BMAA), the known neurotoxin beta-N-oxalylamino-L-alanine (BOAA) was detected from the seeds of Macrozamia moorei and M. communis, and delta-N-oxalyl-ornithine was obtained from the Cycas revoluta seeds. A novel nonprotein amino acid named cycasindene, previously reported from C. revoluta, was also found in the seeds of members of the C. angulata and C. rumphii complex. Eight additional known nonprotein amino acids were also identified. This is the first report of the neurotoxin BOAA from cycad seeds.

Amino Acids↗
PubMed1997

Characterization of glutamine and glutamate transport in rat lung plasma membrane vesicles.

Insufficient glutamine for the lungs during sepsis may contribute to an impairment in lung function. Lung glutamine metabolism is supported by both blood glutamine uptake and de novo biosynthesis using circulating glutamate as a precursor. Information regarding the specific plasma membrane carriers involved in this uptake is lacking. Furthermore, the effect of sepsis on amino acid transport in whole lung has not been studied. We isolated lung plasma membrane vesicles (LPMVs) from control and LPS-treated rats and assayed glutamine and glutamate transport activity in LPMVs. Vesicle purity and functionality were confirmed by time-dependent concentrative amino acid uptake in the presence of Na+, impoverishment of microsomal enzymes, and a 25-fold enrichment in the plasma membrane marker 5'-nucleotidase. Eighty percent of glutamine uptake in lung vesicles was mediated via the high affinity Na(+)-dependent carrier System ASC (Vmax = 80 +/- 10 pmole/mg protein/15 sec; Km = 224 +/- 30 microM) while 19% occurred via the Na(+)-independent System ASC (Vmax = 11 +/- 2 pmole/mg/15 sec; Km = 141 +/- 23 microM). Ninety percent of glutamate transport was mediated by the Na(+)-independent System XAG-. Treatment of rats with LPS resulted in a decrease in both glutamine and glutamate transport in LPMVs. LPMVs offer a novel method for characterizing lung amino acid transport and studying the effects of catabolic states on this activity. The effects of endotoxin on System ASC and XAG- activity may contribute to reduced lung glutamine availability during septic states which may impair cellular metabolism and function.

5'-Nucleotidase↗
PubMed1997

Angiographic predictors of neointimal thickening after successful coronary wall healing following percutaneous revascularization.

This study was undertaken to characterize, by intracoronary ultrasound technique, the neointimal thickening at follow-up of treated coronary segments after successful arterial wall repair and to compare the findings with serial angiographic studies. We selected for study 81 patients with single-vessel coronary disease successfully treated by percutaneous revascularization who were angiographically and ultrasonically reevaluated at a mean follow-up time of 22 +/- 21 months; 23 had been treated by balloon angioplasty, 27 by directional atherectomy, and 31 by elective Palmaz-Schatz stent implantation. The late maximal neointimal thickness varied between 0.1 and 1.5 mm (mean 0.65 +/- 0.31 mm), and the neointimal area ranged between 0.97 and 14.9 mm2 (mean 5.19 +/- 3.14 mm2). The neointimal repair was thinner in patients who obtained a better acute angiographic result immediately after treatment and in stented (3.4 +/- 1.8 mm2) versus dilated (7.8 +/- 4.1 mm2) or resected (5 +/- 1.6 mm2, p < 0.001) segments. On the contrary, the repaired neointimal layer was thicker in those patients who angiographically exhibited less late luminal loss or even expansion and in those evaluated after a longer time since treatment. The acute gain and the time influence resulted in independent predictors of the degree of neointimal thickness. These findings suggest that two reparative mechanisms of the coronary wall may operate in close relation.

Angioplasty, Balloon, Coronary↗
PubMed1997

Nonprotein amino acids from Cycas revoluta.

Two nonprotein amino acids, cycasindene and cycasthioamide, along with eight known nonprotein amino acids, were isolated from the seeds of Cycas revoluta Thunb. The structures of cycasindene and cycasthioamide were elucidated as 3-[3'-amino-indenyl-2]-alanine (1) and N-[glycinyl-alaninyl-11-thio]-5-one-pipecolic acid (2) by chemical and spectral methods.

Alanine↗
PubMed1997

[Differential display analysis of human fetal brain mRNAs and isolation of brain-specific novel ESTs].

Using the differential display technique (DDRT-PCR) originally developed by Liang and Pardee, we tried to isolate the stage-specific or tissue-specific genes in the developing human neural system (brain). With about fifty sets of arbitrary primers and anchored primers, DDRT-PCR was carried out to analyze the differentially expressed mRNAs between human fetal brains of different developmental stage or different parts of human fetal brain at the same developmental stage. About one hundred bands containing cDNA fragments of differential interest were cut out from the polyacrylamide gel, thirty-four of which were cloned and sequenced. They were accepted as novel cDNA sequences by GeneBank. In order to check the feasibility of DDRT-PCR, three of the thirty-four cDNA sequences were randomly chosen as probes for further analysis by dot blot RNA hybridization, and two proved to be specifically expressed in human brain.

Brain Chemistry↗
PubMed1997

[Primary stent treatment in the acute phase of myocardial infaction].

INTRODUCTION: Although direct balloon angioplasty has emerged as an alternative to thrombolytic therapy in patients with acute myocardial infarction, reocclusion and restenosis rates are limiting factors. We postulated that these limitations could be partly overcome by primary stenting of the responsible lesion. MATERIAL AND METHODS: Since January/94 we have studied 59 patients with acute myocardial infarction who were treated in the early phase (3.1 +/- 2 hours since the onset of symptoms) by elective Palmaz-Schatz stent implantation. No adjunctive thrombolytic therapy was associated. Two patients were in cardiogenic shock and were treated under percutaneous cardiopulmonary support. At cardiac catheterization a left ventriculography and coronary angiograms were obtained. Then, mechanical recanalization of the responsible lesion was performed. If the angiographic anatomy was considered suitable, a stent was implanted at the lesion. RESULTS: The infarct related artery was the left anterior descending in 29 patients, the circumflex in 14 and the right coronary artery in 16. At baseline conditions, 40 patients had a totally occluded artery and 19 showed a TIMI-grande 1 antegrade flow. One patient had an early clinical recurrence 4 days later, which required an additional divided Palmaz-Schatz stent at the distal portion of the lesion, in order to seal a residual dissection. All remaining patients had a favourable clinical course without major complications. Immediately after treatment the minimal lumen diameter was 3.2 +/- 0.4 mm and no residual stenosis was detectable at the treated segment. Six-month angiographic reevaluation was performed in all 29 (49%) eligible patients. Restenosis (> 50% stenosis) was detected in 6 out of the 29 evaluated patients (21%). CONCLUSIONS: Primary stent implantation in selected patients with an evolving myocardial infarction provides good initial and 6-month results.

Acute Disease↗
PubMed1996

Trafficking of major histocompatibility complex class II molecules through intracellular compartments containing HLA-DM.

The endosomal site(s) where MHC class II molecules become competent to bind antigenic peptide has not been completely characterized. We identified endocytic compartments through which newly synthesized MHC class II molecules move prior to their expression on the plasma membrane. The compartments co-sediment with lysosomes in the most dense regions of Percoll gradients. The appearance of proteolytic fragments of the invariant chain (I chain), namely leupeptin-induced proteins (LIPs) and class-II-associated invariant chain peptides (CLIP), in this region of the gradient suggests that the release of MHC class II molecules from I chain association occurs within these vesicles. The formation of SDS-stable alpha beta dimers indicated that MHC class II molecules contained within these compartments are receptive to peptide binding. A majority of the HLA-DM protein was found in the same region of the Percoll gradient, consistent with its established function in MHC class-II-restricted antigen presentation. Immunoelectron micrographs of dense-sedimenting compartments indicated that I chain, MHC class II, and DM molecules are contained within both multivesicular and multilamellar vesicles. The final stages of I chain dissociation from MHC class II molecules and DM-mediated peptide loading probably occur in these compartments.

Antigen Presentation↗
PubMed1996

Reduction of thrombotic and hemorrhagic complications after stent implantation.

This study compared two consecutive antithrombotic strategies after Palmaz-Schatz stent implantation and involved 918 patients. Patients treated between May 1991 and May 1994 (group 1; n = 379) received aspirin, dipyridamole, and intravenous unfractionated heparin until oral anticoagulation was effective, between June 1994 and August 1995, 539 patients (group 2) were treated for 1 month with subcutaneous low-molecular-weight heparin (Fragmin), ticlopidine, and aspirin. There were no differences between the groups in terms of sex, clinical condition, vessel diameter, and severity and location of stenosis. Patients in group 1 were younger than those in group 2 (4% were > 70 years old compared with 12%, respectively; p < 0.01). Group 1 patients had more frequent unplanned stenting (48% vs 18%, respectively; p < 0.01) and fewer endoprostheses in the same artery than those in group 2 (1.1 +/- 0.5 vs 1.2 +/- 0.5, respectively; p < 0.01). Among group 2 patients, there was a significant reduction in thrombotic and hemorrhagic complications compared with group 1 patients. No subacute thrombosis occurred in patients in group 2 in contrast with a 5.8% incidence in patients in group 1 (p < 0.01). In addition, a lower incidence of groin and systemic bleeding was observed in patients in group 2 compared with patients in group 1 (2.6% vs 15%, respectively; p < 0.01). The association of low-molecular-weight heparin and antiplatelets provides a simpler antithrombotic strategy in patients treated with intracoronary stents and reduces the incidence of stent thrombosis and hemorrhagic complications. Our findings suggest that this antithrombotic regimen may prevent or completely avoid stent thrombosis.

Acute Disease↗
PubMed1996

[Directional coronary atherectomy in ostial lesions of the anterior descending coronary artery].

INTRODUCTION AND OBJECTIVES: Coronary stenoses at ostial level, when treated by balloon angioplasty, show a primary success rate much lower than those located in other parts of the coronary tree. Balloon dilation of lesions located at the left anterior descending ostium is associated with a high degree of restenosis, elastic recoil and the possibility of retrograde dissection to the left main coronary artery. Simpson atherectomy may be considered a percutaneous alternative in this particular location, since this technique produces fewer incidents of elastic recoil than balloon dilation. The purpose of the present study is to evaluate directional atherectomy in the treatment of patients with symptoms deriving from severe to stenosis at the origin of the left anterior descending artery. MATERIAL AND METHODS: From a total number of 302 patients treated by Simpson atherectomy, we have analyzed 45 with severe stenosis at the left anterior descending ostium (less than 3 mm from its origin). The mean age was 54 +/- 12 years. Eighty two percent of the patients were male. The clinical condition was stable in unstable in 34; eleven had had a previous myocardial infarction. Six had multivessel coronary disease, all of them underwent combined balloon angioplasty of other segments. The treated lesion was native in 41 patients and previously dilated by balloon (restenosis) in 4. Two patients needed balloon predilation with 2 and 2.5 mm to facilitate the pass of the atherocatheter. The size of the Simpson atherocatheter was mainly 7F (78%). The weight of the resected arteriosclerotic material was 11 +/- 7 mg. RESULTS: Primary success (residual stenosis < 40% without major complications) was obtained in 42 out of 45 patients (93%); 3 patients (7%) had major complications (1 death, 1 emergency surgery, and 1 non-Q wave myocardial infarction). A follow-up angiography study was available in 31 patients 7 +/- 8 months later. Restenosis was evidenced in 12 (39%). CONCLUSIONS: Simpson atherectomy for left anterior descending artery ostial lesions is an effective transluminal alternative in selected patients providing a high rate of primary success (93%) and an acceptable restenosis rate (39%).

Adult↗