[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.

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.

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.

Obliteration of femoral pseudoaneurysm complicating coronary intervention by direct puncture and permanent or removable coil insertion

We report on percutaneous obliteration of femoral pseudoaneurysm complicating percutaneous coronary interventions in 6 patients. Our findings suggest that permanent or transient direct coil insertion may be an useful alternative in the treatment of pseudoaneurysm in patients who do not respond to mechanical compression.

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.

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.

[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.

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.

[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.

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.

[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%).

[Addison's disease in pregnancy: a report of six cases]

OBJECTIVE

To review six cases of pregnancy with Addison's disease at Obstetrics and Gynecology Hospital, Shanghai Medical University from 1949 to 1994.

METHOD

This is a clinical retrospective analysis. Five of the 6 patients were treated with hormone replacement therapy, and the remaining one received no hormone treatment due to lack of symptoms during pregnancy and neglect of previous adrenal surgery by obstetricians.

RESULTS

The patient received no treatment occurred Addisonian crisis and died soon after delivery. The other five patients had smooth course of delivery and postpartum period.

CONCLUSIONS

Hormone replacement therapy is important for patients with Addison's disease in pregnancy especially for acute decompensation of adrenal function. Pregnant women with history of adrenal surgery should be monitored carefully even without any symptoms and hormone treatment is necessary. Vaginal delivery is encouraged unless there is obstetric indication.

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.

Lipopolysaccharide and tumor necrosis factor stimulate lung microvascular arginine uptake, a response attenuated by dexamethasone

BACKGROUND

Lipopolysaccharide (LPS), tumor necrosis factor-alpha, (TNF), and glucocorticoids can modulate endothelial nitric oxide (NO) production. L-Arginine is the exclusive precursor for NO biosynthesis, suggesting that NO generation and arginine transport are intimately linked.

METHODS

To further study this relationship, we examined the effects of LPS, TNF, and dexamethasone (DEX) on arginine uptake by rat lung microvascular endothelial cells. The transport of radiolabeled arginine was assayed in confluent cells grown in 24-well plates.

RESULTS

The bulk (> 90%) of arginine transport was mediated by the Na(+)-independent carriers System y+ and System b0,+. Arginine transport was stimulated independently by LPS and TNF, a response first observed at 10 hours. Together, both agents exerted an additive effect on carrier-mediated uptake. The LPS- and TNF-induced increase in arginine transport activity was blocked by cycloheximide and actinomycin D, indicating the requirement for RNA and protein synthesis. The enhancement in transport activity was primarily due to an increase in Systems y+ maximal transport capacity (Vmax) with no change in transporter affinity and little change in System b0,+ activity. Treatment of cells with dexamethasone inhibited arginine transport activity in a time- and dose-dependent manner, an event that was abrogated by both actinomycin D and cycloheximide. The combination of DEX and LPS and TNF abrogated each other's antagonistic effects.

CONCLUSIONS

These data indicate that LPS and TNF additively stimulate arginine transport in lung microvascular endothelial cells via a pathway that requires de novo protein synthesis (possibly of the transporter protein itself) and that this response is attenuated by DEX.

Inhibition of pulmonary microvascular endothelial glutamine transport by glucocorticoids and endotoxin

BACKGROUND

During septic states, the lungs produce increased amounts of glutamine, an event that is mediated by both endotoxin and glucocorticoid hormones and is presumed to be due to accelerated intracellular glutamine biosynthesis. Because enhanced net glutamine release in vivo could also be due to a decrease in cellular uptake, we assayed glutamine transport in cultured rat microvascular pulmonary endothelial cells.

METHODS

The effect of Escherichia coli endotoxin (LPS, 1 microgram/mL), various cytokines, and dexamethasone (DEX, 0.1 mumol/L) on glutamine transport activity was studied in rat lung microvascular endothelial cells grown in varying glutamine concentrations (0, 0.1, 0.5, and 2 mmol/L). Experiments were also performed in cells treated with cycloheximide, actinomycin D, or chelerythrine chloride.

RESULTS

More than 90% of glutamine transport was mediated by the Na+ -dependent transport system ASC. DEX and LPS inhibited endothelial glutamine uptake in a time- and dose-dependent manner, a response that was only observed with incubation medium contained the lower concentrations of glutamine. Neither DEX nor LPS altered transport activity in cells cultured in medium containing 2 mmol glutamine/L. There was no synergistic or additive effect when both compounds were added together. The cytokines tumor necrosis factor alpha, interleukin (IL) 1, IL-2, and IL-6 did not alter glutamine transport. both DEX and LPS inhibited glutamine transport by decreasing transporter maximal transport velocity (Vmax) without affecting transporter affinity (Km). Cycloheximide and actinomycin D abrogated the inhibition of transport activity that was observed in DEX- or LPS-treated cells, whereas the protein kinase C inhibitor chelerythrine chloride had no effect on either control or stimulated glutamine transport.

CONCLUSIONS

These data suggest that DEX and LPS "down-regulate" glutamine uptake by lung microvascular endothelial cells by inducing the synthesis of an inhibitory protein that modulates the activity of the system ASC protein. This response in vitro appears to be influenced by the extracellular glutamine concentration. This decrease in microvascular endothelial glutamine transport may be one mechanism by which net lung glutamine release is enhanced during critical illness.

Protein kinase C-dependent regulation of L-arginine transport activity in Caco-2 intestinal cells

The regulation of plasma membrane L-arginine transport activity was investigated in differentiated and undifferentiated states of the human intestinal cell line, Caco-2. The sodium-independent, leucine-insensitive uptake of L-arginine measured in this study has been assigned by us previously to system y+ in Caco-2 cells. Treatment of cells with serum-free media containing epidermal growth factor (EGF), transforming growth factor alpha (TGF alpha), or the protein kinase C (PKC) activator 12-O-tetradecanoylphorbol 13-acetate (TPA), stimulated system y+ arginine transport activity in Caco-2 cells. Transport upregulation by these growth factors or by TPA was blocked by cycloheximide or the PKC inhibitor chelerythrine. Arginine uptake was diminished during the course of differentiation, attributable to a reduction in the transport system y+ capacity (Vmax) with no change in apparent affinity (Km). TPA stimulated arginine uptake required at least 3 h of continual exposure, and increased the membrane's transport capacity (Vmax) in both undifferentiated and differentiated cells. TPA elevated the diminished transport Vmax of differentiated cells TPA to the elevated Vmax value associated with undifferentiated cells. We conclude that upregulation of arginine transport is part of a pleiotropic response to EGF/TGF alpha, and that this involves PKC and de novo synthesis of polypeptides associated with system y+ transport activity.

Amino acid metabolism and the vascular endothelium: regulation and disease implications

Amino acid metabolism by the vascular endothelium is a complex process that often begins with the carrier-mediated uptake of circulating amino acids into the endothelial cytoplasm. Amino acids are essential for maintaining intact endothelial functions, which include cell proliferation, regulation of blood flow and vascular tone, coagulation and fibrinolysis, and metabolism of a variety of macromolecules. The disturbances in endothelial amino acid transport and metabolism that occur during infection and inflammation are due, in part, to changes in substrate availability and to the local and/or systemic elaboration of specific mediators. An improved understanding of endothelial amino acid metabolism will not only provide new knowledge regarding disease mechanisms and regulation, but may also lead to new treatment strategies that may include the clinical use of specific nutritional formulas.

Protein kinase C activation inhibits glutamate transport by endothelial cells

The role of protein kinase C (PKC) in regulating endothelial cell glutamate transport was investigated. Glutamate transport studies were performed in confluent human umbilical vein endothelial cells which were treated with the phorbol ester 12-myristate 13-acetate (TPA, 0-1000 nM), a compound which directly activates PKC. TPA inhibited Na(+)-independent System xAG- glutamate transport by 70% but only slightly reduced Na(+)-dependent activity. The TPA-mediated reduction in transport activity was dose-dependent, beginning at 5 min and lasting for at least 24 hr. TPA inhibition of glutamate transport had two distinctive phases: an acute phase (< 1 hr, not affected by either cycloheximide or actinomycin D) in which TPA decreased System xAG- glutamate transporter affinity (TPA Km = 522 +/- 25 microM vs control Km = 329 +/- 85 microM, P < 0.01) but did not alter transporter capacity (TPA Vmax = 4426 +/- 230 pmole/mg/min vs control Vmax = 4535 +/- 750 pmole/mg/min, P = NS) and a chronic phase (4-24 hr) in which TPA inhibition of glutamate transport was due to a reduced transporter capacity (Vmax = 2895 +/- 570 pmole/mg/min) without altering transporter affinity (Km = 370 +/- 60 microM glutamate) and was abrogated by cycloheximide or actinomycin D. The protein kinase C inhibitor chelerythrine chloride abrogated TPA's inhibition effect in both the acute and chronic phases. These data indicate that protein kinase C activation decreases glutamate transport in human umbilical vein endothelial cells via protein synthesis dependent and independent mechanisms.

Tumor necrosis factor stimulates system XAG- transport activity in human endothelium

System xAG- is responsible for the carrier-mediated Na(+)-independent transport of anionic amino acids such as glutamate and aspartate across the plasma membrane of cells. In order to examine a possible role for cytokines in regulating System xAG- activity, the effect of TNF on [3H]glutamate transport in cultured human umbilical vein endothelial cells (HUVECs) was studied. Carrier-mediated glutamate uptake was accomplished by two high-affinity carriers, predominantly by a Na(+)-independent carrier (System xAG-, 75% of total glutamate uptake) and, to a lesser extent by a Na(+)-dependent carrier (System XAG-, 24% of total uptake). TNF treatment (10 ng/ml for 10 hr) resulted in an 80% increase in Na(+)-independent glutamate transport activity with no change in System XAG- activity. The TNF stimulatory effect was blocked by actinomycin D and cycloheximide. TNF treatment increased System xAG- glutamate transporter Vmax by 51% (control Vmax = 2359 +/- 345 pmole/mg protein/min vs TNF Vmax = 3569 +/- 436 pmole/mg protein/min, P < 0.01) without altering transporter affinity (control Km, 229 +/- 40 microM glutamate vs TNF Km = 224 +/- 60 microM glutamate, P = NS). The protein kinase C (PKC) inhibitor chelerythrine chloride had no effect on the TNF-stimulated glutamate transport, indicating that the augmented glutamate transport was not mediated by PKC activation. These data indicate that the TNF-stimulated glutamate transport in HUVECs requires do novo protein synthesis, possibly of the System xAG- transporter protein itself. Accelerated glutamate transport provides a precursor for the biosynthesis of macromolecules and glutamine.

TNF-stimulated arginine transport by human vascular endothelium requires activation of protein kinase C

OBJECTIVE

The authors determined the endothelial arginine transport mechanism and the potential role of a tumor necrosis factor (TNF)-alpha-mediated signal transduction pathway involving protein kinase C (PKC) in regulating this transport in cultured endothelial cells.

SUMMARY BACKGROUND DATA

The vascular endothelium metabolizes arginine to generate nitric oxide (NO), and an increase in NO production can be stimulated by several cytokines. The mechanism(s) responsible for the accelerated arginine transport are poorly understood.

METHODS

Arginine transport was assayed in confluent human umbilical vein endothelial cells in the presence of TNF +/- the PKC inhibitor chelerythrine chloride.

RESULTS

Carrier-mediated arginine transport was accomplished by two Na(+)-independent transporters, System y+ (80% of total transport) and System b0,+ (20% of transport). Tumor necrosis factor (0.1-2 ng/mL) increased System y(+)-mediated arginine transport in a time- and dose-dependent manner by augmenting System y+ transport maximal capacity (control Vmax = 1325 +/- 60 pmol/mg protein/minute vs. TNF Vmax = 3015 +/- 110 pmol/mg protein/minute, p < 0.01) without affecting transporter affinity (control Km = 30 +/- 1.4 microM vs. 34 +/- 1.3 microM arginine, p = NS). Stimulation was maximal at the 8-hour time point and was inhibited by both actinomycin D and cycloheximide. In addition, inhibition of PKC with chelerythrine abrogated the TNF-augmented arginine transport. Similarly, incubation of cells with the direct PKC activator TPA (phorbol ester 12-myristate 13-acetate) stimulated System y(+)-mediated arginine transport nearly fivefold, secondary to an increase in transporter Vmax (TPA Vmax = 5349 +/- 310 pmol/mg protein/minute, p < 0.001 vs. control), with no change in Km. This TPA-induced stimulation of arginine transport also was blocked by chelerythrine CI, actinomycin D, and cycloheximide. Incubation of TNF-stimulated cells with two NO synthase inhibitors did not reduce transport activity, suggesting that the arginine transporter and the NO synthase enzyme may, in part, be independently regulated.

Balloon-expandable stent repair of 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. This study evaluates the feasibility and immediate results of balloon-expandable stent implantation in 10 patients with severe coarctation of aorta. The ages of the patients ranged from 1 month to 43 years; 1 was an infant, 8 were children (mean age 5.3 +/- 4 years), and 1 was an adult. All had an unfavorable anatomy for balloon angioplasty; 9 had isthmus hypoplasia. Balloon predilation was first performed and its immediate effect evaluated. Then a balloon-expandable stent that was 30 mm long and covered the isthmus and coarctation levels was deployed, and it was further expanded to the preselected final diameter (12 +/- 4 mm). A final hemodynamic and angiographic evaluation was then obtained. Full deployment of an incompletely expanded and distally displaced stent in the infant led to aortic disruption that was controlled by a second stent covering the disrupted zone and the isthmus. After balloon angioplasty alone was done, the mean gradient (43 +/- 12 vs 31 +/- 10 mm Hg) and the percentage stenosis (72% +/- 11% vs 54% +/- 11%) had an insufficient decrease. However, after stent implantation was done, the gradient almost disappeared (mean 2 +/- 3 mm Hg). The angiographic stenosis disappeared in 7 patients and was markedly reduced in 3. The ratio of isthmus/descending aorta changed from 0.65 +/- 0.14 to 1 +/- 0.08 (p < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Regulation of system y+ arginine transport capacity in differentiating human intestinal Caco-2 cells

This study describes the ability of passaged human intestinal Caco-2 cells to regulate transport of L-arginine via system y+. Subconfluent and confluent cells possessed system y+ activity, as determined by the sodium independence of uptake and the pattern of inhibition by amino acid analogues or N-ethylmaleimide. Initial rates of arginine uptake via system y+ decreased as the cells advanced from the undifferentiated to the differentiated state following culture passaging. Furthermore, kinetic analysis of the leucine-insensitive portion of uptake indicated that the Caco-2 system y+ transport capacity decreased with cell age, dropping from a maximal velocity (Vmax) = 1,094 pmol.mg-1.min-1 [Michaelis constant (Km) = 41 microM] in undifferentiated cells 2 days postseeding to Vmax = 320 pmol.mg-1.min-1 (Km = 37 microM) in confluent cells 9 days postseeding (from cells of the same passage). Northern analysis indicated that the levels of a single 7.9-kb mCAT-1 mRNA species were relatively constant over the course of Caco-2 differentiation and therefore were unsynchronized with the system y+ relative transport activities. It is concluded that the Caco-2 capacity to transport arginine via system y+ may be downregulated by posttransitional modifications in confluent cells compared with newly passaged undifferentiated cells. These data serve as a well-defined in vitro model for further studies regarding regulation of arginine transport in epithelial cells.