Isolation and characterization of tissue-type plasminogen activator- binding proteoglycans from human umbilical vein endothelial cells

We analyzed the tissue-type plasminogen activator (TPA)-binding proteoglycans (PGs) on human umbilical vein endothelial cells (HUVECs), which were metabolically labeled with [35S]NA2SO4. Cell extracts were then prepared and subjected to affinity chromatography on diisopropyl fluorophosphate (DFP)-inactivated TPA-Sepharose 4B. Approximately 6% of the incorporated 35S radioactivity bound to DFP-treated TPA-Sepharose 4B and was eluted with 2 mol/L NaCl. In addition to NaCl, heparin, arginine, and lysine but not glycine, epsilon-amino-n-caproic acid or aspartic acid inhibited this binding and eluted the bound 35S radioactivity. Urea-containing polyacrylamide gel electrophoresis of the eluted material consistently revealed two main signals of 35S radioactivity (one with an M(r) between 600,000 and 750,000 [PGA] and the other with an M(r) between 120,000 and 180,000 [PGC]). Occasionally a less intense signal with an M(r) between 340,000 and 440,000 (PGB) was seen. Heparitinase treatment markedly decreased the intensities of both 35S signals (PGA and PGB), and chondroitinases AC and ABC abolished the 35S signal of PGC, indicating that most of the HUVEC-incorporated radioactivity with an affinity for TPA could be attributed to heparan sulfate- and chondroitin sulfate-like structures. Reductive elimination, which was performed to separate the possible glycosaminoglycan moieties from the core proteins, confirmed the PG-like nature of this material and again revealed heparan sulfate and chondroitin sulfate as the major glycosaminoglycan components. We therefore conclude that HUVECs synthesize TPA-binding, heparan sulfate- and chondroitin sulfate-containing PGs. In vivo, similar PGs may play a role in TPA binding to endothelial cells and thereby possibly influence TPA activity and/or provide an intravascular storage pool of TPA.

Protein C inhibitor (PCI)

PCI is a non-specific serpin that inhibits several proteases of the coagulation and fibrinolytic systems as well as plasma- and tissue kallikreins and the sperm protease acrosin. The precise physiological role of PCI has not been defined yet. Heparin stimulates most PCI/protease reactions, but interferes with the tissue kallikrein/PCI-interaction. Thereby heparin not only regulates PCI-activity but also its specificity in systems containing two or more of its target proteases. This effect is not restricted to heparin, but is also seen with other glycosaminoglycans (GAGs) and large, negatively charged molecules. PCI also binds to GAGs present on the surface of epithelial kidney cells, and GAGs isolated from these cells have a similar effect on PCI activity as heparin. Studies analyzing the role of PCI as an acrosin inhibitor revealed that endogenous PCI is immunocytochemically localized to disrupted acrosomal membranes of morphologically abnormal sperms, while intact sperms are negative for PCI-antigen. In a mouse in vitro fertilization model human PCI inhibited sperm/egg binding and decreased the fertilization rate. Northern blotting of human and mouse mRNA using human and mouse PCI-cDNA probes revealed that in the mouse PCI is exclusively synthesized in the genital tract (testis, seminal vesicle, ovary), while in humans PCI is additionally synthesized in many other organs (e.g., liver, pancreas, heart). Therefore PCI might regulate enzymes involved in fertilization (e.g. acrosin) in both species. Other proteases (e.g., tissue kallikrein) are possibly regulated in a species specific manner by different inhibitors.

Rapana thomasiana grosse (gastropoda) haemocyanin: spectroscopic studies of the structure in solution and the conformational stability of the native protein and its structural subunits

1. The stability towards pH changes, thermal and chemical (guanidine hydrochloride) denaturation of the oxy- and apo-forms of the native Rapana thomasiana haemocyanin and its structural subunits, RHSS1 and RHSS2, has been investigated using fluorescence and CD spectroscopy. The association of the subunits into haemocyanin aggregates increases considerably the melting temperature and the free energy of stabilization in water. The guanidine hydrochloride denaturation of the aggregated oxygen-transporting protein depends slightly on the protein concentration. The denaturation of the individual subunits is concentration-independent. Rapana haemocyanin is 5.9-7.5 kJ/mol more stable than the constituent polypeptide chains. 2. Upon excitation of the native haemocyanin and the subunits at 295 or 280 nm the fluorescence emission is determined by tryptophyl residues 'buried' deeply in the hydrophobic interior of the protein globules. This is confirmed by quenching experiments with acrylamide, caesium and iodide ions. The efficiency of the radiationless energy transfer between the phenol (donor) and indole (acceptor) fluorophores in the three species, native haemocyanin, RHSS1 and RHSS2, has been determined. An efficient 'interchain' energy transfer between tyrosyl and tryptophyl residues from different polypeptide chains occurs in the non-dissociated form of the haemocyanin. 3. The tryptophan emission of the oxyhaemocyanin, oxy-RHSS1 and oxy-RHSS 2 is strongly quenched by the copper-dioxygen complex at the active site and the respective quantum yields of fluorescence of the oxygenated species are 4-7 times lower than those of the apo-forms. Protonated imidazole groups quench the fluorescence of neighbouring exited indole rings, probably by charge-transfer complex formation.

Reevaluation of the pathway for the metabolism of 7,10,13, 16-docosatetraenoic acid to 4,7,10,13,16-docosapentaenoic acid in rat liver

When rat liver microsomes were incubated with [1-14C]22:4(n-6) under standard conditions for measuring acyl-CoA desaturases, it was not possible to detect the synthesis of any 22:5(n-6). When malonyl-CoA and NADPH were included in the incubation, 22:4(n-6) was chain elongated to 24:4(n-6), which was then desaturated to 24:5(n-6). Rat hepatocytes metabolized [1-14C]22:4(n-6), [3-14C]24:4(n-6), and [3-14C]24:5(n-6) to yield esterified radioactive 22:5(n-6). The results show that 22:4(n-6) is the precursor of 22:5(n-6) but the pathway is independent of an acyl-CoA-dependent 4-desaturase and probably requires intracellular communication between the endoplasmic reticulum and a site for beta-oxidation. Microsomal reaction rates for (n-6) versus (n-3) polyunsaturated fatty acid biosynthesis cannot per se be used to explain why in vivo most membrane lipids preferentially accumulate 22:6(n-3) rather than 22:5(n-6). Rates of desaturation of 24:4(n-6) and 24:5(n-3) at position 6 were similar (M. Geiger et al., Biochim. Biophys. Acta 1170, 137-142, 1993). We now show that 20:4(n-6) and 20:5(n-3) are chain elongated at the same rate as are 22:4(n-6) and 22:5(n-3). At present, no single reaction can be defined as being substrate specific or rate limiting to explain why there is an apparent selective synthesis and acylation of 22:6(n-3) rather than 22:5(n-6) into membrane lipids.

Inhibition of acrosin by protein C inhibitor and localization of protein C inhibitor to spermatozoa

Protein C inhibitor (PCI) is synthesized by cells throughout the male reproductive tract and is present in high concentrations (220 micrograms/ml) in seminal plasma. Seminal plasma as well as the acrosome of spermatozoa are rich in possible target proteases for PCI. We analyzed the interaction of PCI with acrosin, a serine protease stored in its zymogen form in the acrosome of spermatozoa. Purified human PCI inhibited the amidolytic activity of purified boar acrosin with an apparent second-order rate constant of 3.7 x 10(4) M-1.s-1. Inhibition was paralleled by the degradation of PCI from its 57- to its 54-kDa form. Human PCI also inhibited the amidolytic activity of activated human sperm extracts and formed complexes with acrosin as determined by an enzyme-linked immunosorbent assay. Immunocytochemistry revealed that morphologically abnormal spermatozoa stained for PCI antigen, whereas morphologically normal spermatozoa were negative. In immunoelectron microscopy, PCI was exclusively localized in the immediate vicinity of disrupted acrosomal membranes of sperm heads. These data suggest that PCI might function as a scavenger of prematurely activated acrosin, thereby protecting intact surrounding cells and seminal plasma proteins from possible proteolytic damage.

Binding of urinary protein C inhibitor to cultured human epithelial kidney tumor cells (TCL-598). The role of glycosaminoglycans present on the luminal cell surface

Binding of urinary protein C inhibitor (PCI) to cultured human epithelial kidney tumor cells (TCL-598) was studied. Binding was dose-dependent, time-dependent, and saturable. Heparin interfered in a dose-dependent way with PCI binding to TCL-598 as did heparan sulfate and to a lesser degree also dermatan sulfate. Pretreatment of TCL-598 with protamine sulfate inhibited subsequent binding of PCI in a dose-dependent manner and > 100 micrograms/ml protamine sulfate reduced binding of PCI to < 10% of the control. Binding of 125I-PCI was specific, and bound 125I-PCI was recovered from the cells by heparin treatment or detached together with intact cells by EDTA treatment, migrated on sodium dodecyl sulfate-polyacrylamide gel electrophoresis with the same mobility (M(r) = 57,000) as unbound 125I-PCI. Furthermore, cell-bound PCI was functionally active as judged from its ability to inhibit the amidolytic activity of urokinase, and its inhibitory activity was stimulated approximately 3-4-fold as compared to fluid-phase PCI. Immunogold electron microscopy revealed that PCI-antigen presented to the cells from the luminal side bound exclusively to that surface in native as well as in prefixed cells. This binding of PCI was abolished in the presence of heparin (50 micrograms/ml) and after pretreatment of the cells either with protamine sulfate (400 micrograms/ml) or with heparinase III (0.5 unit/ml). A slight decrease in PCI binding was seen after pretreatment of the cells with chondroitinase ABC and chondroitinase AC. In contrast, binding of PCI to extracellular matrices of TCL-598 was decreased to approximately 70% after chondroitinase ABC treatment of the extracellular matrices, whereas both heparinase III or chondroitinase AC treatment only reduced matrix-bound PCI to approximately 95%. These data suggest that heparan sulfate-containing proteoglycans are predominantly involved in binding of PCI to the luminal side of TCL-598, while dermatan sulfate-containing proteoglycans, the overall predominant PCI-binding proteoglycans in TCL extracts, are responsible for PCI binding to the extracellular matrix. Heparan sulfate, however, exposed to an environment containing PCI under physiological conditions, might localize PCI and modulate its target enzyme specificity in vivo.

Catecholestrogens are MCF-7 cell estrogen receptor agonists

Catecholestrogens are important metabolites of estradiol and estrone in the human. Considerable interest has focused on the catecholestrogens 2-hydroxy- and 4-hydroxyestradiol since they bind to the estrogen receptor with an affinity in the range of estradiol. Using the MCF-7 cell line, we analysed the capacity of purified catecholestrogens to transform the estrogen receptor into its high affinity nuclear binding form and to affect receptor-dependent processes such as proliferation and expression of the progesterone receptor (PR). Incubations with 2-hydroxy- and 4-hydroxyestradiol at 10(-8) M for 1 h resulted in tight nuclear binding of the estrogen receptor. During treatment of the cells with catecholestrogens we obtained a marked increase in proliferation rate of 36 and 76% for 2-hydroxy- and 4-hydroxyestradiol, respectively, relative to the inductive effect of estradiol (100%). The PR level, was slightly increased by treatment with 2-hydroxyestradiol (10%), whereas treatment with 4-hydroxyestradiol increased the PR level at 28%, compared to estradiol (100%). From these results we conclude that the 2- and 4-hydroxylated derivatives of estradiol are active hormones and are able to initiate estrogen receptor mediated processes in MCF-7 cells.

Studies to determine if rat liver contains chain-length-specific acyl-CoA 6-desaturases

According to the revised pathway for 22:6(n - 3) biosynthesis in liver (Voss et al. (1991) J. Biol. Chem. 266, 19995-20000) both 18:3(n - 3) and 24:5(n - 3) serve as substrates for desaturation at position-6. The present study was undertaken to determine whether microsomes contain chain-length-specific 6-desaturases. Addition of [1-14C]20:3(n - 6), a substrate for desaturation at position-5, did not depress desaturation of either [1-14C]18:3(n - 3) or [3-14C]24:5(n - 3). An unexplained observation was that both 18:3(n - 3) and 24:5(n - 3) inhibited the metabolism of 20:3(n - 6) to 20:4(n - 6). When an enzyme-saturating level of [3-14C]24:5(n - 3) was now incubated alone and with 40, 80 and 120 nmol of [1-14C]18:3(n - 3), the production of 24:6(n - 3) was inhibited by 43, 67 and 81%. Conversely, when [1-14C]18:3(n - 3) was incubated with 40, 80 or 120 nmol of [3-14C]24:5(n - 3), the synthesis of 18:4(n - 3) was inhibited by only 15, 20 and 27%. These and other competitive studies showed that there was always preferential desaturation of 18:3(n - 3) rather than 24:5(n - 3). In addition, competitive studies between 18:2(n - 6) and 18:3(n - 3), as well as with 24:4(n - 6) and 24:5(n - 3) showed that there was always preferential desaturation of the (n - 3) acid. Although our results are consistent with a single 6-desaturase, further studies, including the isolation of the 6-desaturases(s), is obviously required to determine whether multiple forms of the 6-desaturase exist.

[Early hemostasis after coronary therapeutic interventions by using a collagen plug]

Significant bleeding at the puncture site is one of the most important problems in the care of patients undergoing interventional coronary procedures like PTCA, rotablation, laser angioplasty or stent implantation. This is due to systemic application of heparin, acetylic salicic acid and, in stent patients, even additional coumadine. Furthermore, the interventional systems implement catheter systems with a large inner and outer lumen leading to increased vessel trauma. To decrease the risk of bleeding and to reduce the time of pressure dressing and bed rest, a bovine collagen plug (VasoSeal) was used in 600 consecutive patients undergoing one of the above-mentioned interventional procedures. In the majority of patients (pts.) (474/600 = 79%) either no (404 pts.) or minimal (70 pts.) bleeding occurred. Bed rest could be reduced from more than 24 h to 6-12 h. In 65/600 pts. (11%) significant bleeding developed which could be controlled by compression. Bed rest in these patients was 13-20 h. Larger bleedings or complications occurred in 61/600 pts. (10.2%) and could be controlled conservatively in all but eight patients. One patient (0.2%) had a narrowing of the artery at the puncture site after the procedure, probably due to intraarterial plug application. In another patient (0.2%) embolization of the plug into the popliteal artery occurred which could be treated by embolectomy using a Fogarty-catheter. Arteriovenous fistulae or aneurysms developed in 8/600 pts. (1.3%) but these are no specific complications of the hemostatic device. The plug could not be placed in 13/600 pts. (2%), mainly in the beginning of the study.(ABSTRACT TRUNCATED AT 250 WORDS)

Variability of different patterns of skin oscillatory flux in healthy controls and patients with peripheral arterial occlusive disease

Variability of patterns of laser Doppler flux motion was analysed at 5 different sites at the foot of 12 healthy controls and 24 patients with different degrees of ischemia due to peripheral arterial occlusive disease. Patterns were evaluated by means of the frequency histogram method. Three main flux motion components were detected at mean frequencies of 3.5 +/- 1.1 min-1 (low frequency waves, LF), 17.2 +/- 2.7 min-1 (high frequency waves, HF) and at 62.6 +/- 8.5 min-1 (pulsatile waves, PF). The characteristic pattern in normals consisted of LF and PF waves. In severe ischemia oscillatory flux was predominantly characterized by the combination of LF and HF waves and loss of pulsatile flux, or by the absence of any flux motion. Claudicants covered the entire spectrum of the flux motion patterns. In controls spatial variations were mainly due to the occasional presence of HF waves at one of the 5 sites. With increasing ischemia spatial variability of HF waves decreased due to more homogeneous presence. Loss of pulsatile flux was inhomogeneous in claudicants but almost complete in severe ischemia. Whereas LF waves were almost always observed at all sites of controls and claudicants there was considerable spatial variability in severe ischemia due to inhomogeneous loss of LF waves. Prevalence of the distinct flux motion patterns was well reproducible in controls and patients. Patterns showed a marked day to day variability when sites of measurement were compared.

Vitronectin modulates glycosaminoglycan dependent reactions of protein C inhibitor

Protein C inhibitor (PCI), a glycosaminoglycan (GAG) dependent serine protease inhibitor, inhibits its target proteases by forming SDS-stable 1:1 complexes. GAGs alter target enzyme specificity of PCI in such a way that e.g. urokinase (uPA) is the preferred target enzyme in the presence of GAGs while in their absence preferentially tissue kallikrein (TK) complexes are formed. The effect of the GAG-binding adhesive glycoprotein vitronectin (Vn) on the GAG-stimulated inhibition of uPA by PCI was studied using an amidolytic assay. In the presence of heparin, Vn protected uPA from inhibition by PCI in a dose-dependent manner with respect to both, Vn- and heparin-concentration. Vn also was active when heparin was replaced by low-molecular weight heparin or heparan sulfate, respectively. In the absence of GAGs, Vn had no effect on the inhibition of uPA by PCI. In a similar system, Vn was far less effective in modifying the inhibitory function of heparin on the inhibition of TK by PCI. When equimolar concentrations of radiolabelled uPA and TK were incubated with PCI in the presence of heparin, only complexes of PCI with uPA were detectable. Addition of Vn reduced this complex formation, whereas, in contrast, complexes of PCI and TK appeared. These results indicate that Vn modulates both, the activity and specificity of PCI and suggest different structural heparin-requirements for the PCI/uPA versus PCI/TK interaction.

Modulation of heparin cofactor II activity by glycosaminoglycans and adhesive glycoproteins

Heparin cofactor II (HCII) is a specific thrombin inhibitor; its inhibitory activity is stimulated by heparin (Hep) and dermatan sulfate (DS). Vitronectin (VN), a heparin binding adhesive glycoprotein present in plasma and extracellular matrix, has been shown to decrease the stimulatory effect of Hep but not of DS on thrombin inhibition by HCII (Preissner and Sié, 1988). We analyzed the effect of glycosaminoglycans (GAGs) and GAG-binding proteins on the HCII/thrombin interaction in more detail. HCII was purified from the supernatant of barium citrate adsorbed normal human plasma by polyethylene glycol precipitation followed by affinity chromatography on heparin-Sepharose CL-6B and ion-exchange chromatography on a QAE-Sephadex A-50. Inhibition of thrombin by HCII was studied in the absence and presence of GAGs (hep 0.03-30 micrograms/ml, DS 0.05-50 micrograms/ml, heparan sulfate (HS) 0.05-50 micrograms/ml) in a chromogenic substrate assay using S-2366 as a thrombin substrate. The effects of VN and fibronectin (FN) on HCII stimulation by GAGs were determined. In addition to Hep and DS the inhibitory effect of HCII was stimulated by HS, however, to a lesser extent. Using 0.03U/ml thrombin and 1nM HCII the stimulatory effect of GAGs was completely inhibited when Hep (less than or equal to 0.3 micrograms/ml) was preincubated with VN (60 micrograms/ml) and decreased to less than 50% when HS (50 micrograms/ml) was preincubated with VN (60 micrograms/ml). VN had no effect on DS as already described previously.(ABSTRACT TRUNCATED AT 250 WORDS)

Inhibition of tissue kallikrein by protein C inhibitor. Evidence for identity of protein C inhibitor with the kallikrein binding protein

We studied the inhibition of tissue kallikrein by protein C inhibitor (PCI), a relatively unspecific heparin-dependent serine protease inhibitor present in plasma and urine. PCI inhibited the amidolytic activity (cleavage of H-D-valyl-L-leucyl-arginine-p-nitroaniline) of urinary kallikrein with an apparent second order rate constant of 2.3 x 10(4) M-1 s-1 and formed stable complexes (85 kDa) with urinary kallikrein as judged from silver-stained sodium dodecyl sulfate-polyacrylamide gels. Complex formation was time-dependent and was paralleled by a decrease in the intensity of the main PCI protein band (Mr = 57,000) and an increase in the intensity of the lower Mr (54,000) PCI form (cleaved inhibitor). Heparin interfered with the inhibition of tissue kallikrein by PCI and with the formation of tissue kallikrein-PCI complexes in a dose-dependent fashion and completely abolished PCI-tissue kallikrein interaction at 300 micrograms/ml. This is in contrast to findings on the interaction of PCI with all other target proteases studied so far (i.e. stimulation of inhibition by heparin) but is similar to the reaction pattern of 125I-labeled tissue kallikrein with so called kallikrein binding protein described in serum and other systems. To study a possible relationship between PCI and this kallikrein binding protein we incubated 125I-labeled urinary kallikrein in serum and in PCI-immunodepleted serum in the absence and presence of heparin and analyzed complex formation using sodium dodecyl sulfate-polyacrylamide gel electrophoresis. In normal serum, formed complexes co-migrated with complexes of purified PCI and 125I-kallikrein and were less intense in the presence of heparin. No complex formation at all was seen in PCI-depleted serum. Our data indicate that PCI may be a physiologically important endogenous inhibitor of tissue kallikrein and provide evidence that PCI may be identical to the previously described kallikrein binding protein.

Possible identity of kallikrein binding protein with protein C inhibitor

Protein C inhibitor (PCI) inhibits tissue kallikrein by forming stable 1:1 complexes (k1 = 2.3 x 10(4)M-1s-1). Heparin inhibits the tissue kallikrein/PCI-interaction and complex formation of 125I-tissue kallikrein in serum. 125I-tissue kallikrein complexes formed in plasma can be immunoprecipitated with monoclonal anti-PCI IgG suggesting that PCI might be identical to the kallikrein binding protein described previously (J. Chao et al. 1986, Biochem. J. 239, 325-331).

Plasminogen activation in diabetes mellitus: kinetics of plasmin formation with plasminogen and tissue plasminogen activator from diabetic donors

Impaired function of the fibrinolytic system might be involved in the development of vascular disease and thromboembolic complications in diabetic patients. We studied kinetics of plasmin formation using t-PA and Pg purified from the plasma of three individual uncontrolled type I diabetic patients. Activation of diabetic Pg by normal t-PA in the presence of stimulating CNBr fragments of fibrinogen exhibited a prolonged lag phase (30 to 60 minutes) until maximally stimulated plasmin formation occurred (normal, 5 to 15 minutes) and substrate inhibition at Pg concentrations more than 10 to 30 nM. When normal Pg was activated by diabetic t-PA in the presence of CNBr-f, differentiation between lag phase and phase of maximal plasmin formation was not possible (activation time was 2 hours) and a high Km (7.5 microM) was calculated. After normalization of metabolic parameters in the patients studied, functional properties of t-PA and Pg improved. Km of diabetic t-PA returned to normal values (0.02 to 0.09 microM) and for diabetic Pg the prolonged lag phase was shortened, indicating that the functional abnormalities were reversible and possibly caused by metabolically induced changes (such as nonenzymatic glucosylation) in the t-PA or plasminogen molecule. We also studied the effect of in vitro glucosylation on functional properties of Pg. Similar, but less pronounced substrate inhibition as with diabetic Pg was observed when this glucosylated Pg was activated by t-PA in a system stimulated by CNBr fragments of fibrinogen. Therefore nonenzymatic glucosylation might explain, at least in part, functional abnormalities observed with Pg from diabetic patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Catheter ablation using radiofrequency current to cure symptomatic patients with tachyarrhythmias related to an accessory atrioventricular pathway

BACKGROUND

Recent investigations have shown that cure of patients with symptomatic tachyarrhythmias related to an accessory atrioventricular pathway may be achieved by closed-chest electrode catheter ablation of the accessory connection. Direct current shocks have primarily been used for this purpose, but its applicability is limited because of the lack of controlled titration of electrical energy, the infliction of barotrauma, and the need for general anesthesia. Radiofrequency current has been proposed as an alternate energy source.

METHODS AND RESULTS

Seventy-three symptomatic patients with Wolff-Parkinson-White syndrome and 19 patients with only retrogradely conducting (concealed) pathways underwent ablative therapy with radiofrequency current. There were 71 accessory pathways located on the left side of the heart (57 free-wall and 14 posteroseptal pathways) and 25 on the right side (11 free-wall, seven posteroseptal, and seven midseptal or anteroseptal pathways). In patients with right-sided pathways, ablation was attempted via a catheter positioned at the atrial aspect of the tricuspid annulus. In patients with a left-sided free-wall accessory pathway, a novel approach was used in which the ablation catheter was positioned in the left ventricle directly below the mitral annulus. Accessory pathway conduction was permanently abolished in 79 patients (86%). Growing experience and improved catheter technology resulted in a 100% success rate after the 52nd consecutive patient. Failures were mainly the result of inadequate catheters used initially or an unfavorable approach to left posteroseptal pathways.

CONCLUSIONS

Catheter ablation of accessory atrioventricular pathways by the use of radiofrequency current is an effective and safe therapeutic modality for patients with symptomatic tachyarrhythmias mediated by these pathways.

Radiofrequency current catheter ablation of accessory atrioventricular pathways

Tachyarrhythmias mediated by an accessory atrioventricular pathway and which are refractory to drug therapy have been treated surgically with variable success. Early results of direct-current catheter ablation were encouraging but were associated with complications such as barotrauma and the need for a general anaesthetic. We have investigated the endocardial application of radiofrequency current which is a potentially safer technique. Of 105 patients with an accessory atrioventricular pathway, 79 were located on the left side of the heart and 32 on the right side. Accessory pathway conduction was permanently abolished in 93 (89%) patients. Complications developed in 3 patients: thrombotic occlusion of a femoral artery, arteriovenous fistula formation at the site of groin puncture, and left ventricular rupture with cardiac tamponade after direct-current shocks. There were no deaths from the procedure. We conclude that radiofrequency current catheter ablation is both effective and safe for patients with symptomatic tachyarrhythmias mediated by accessory atrioventricular pathways.

Urinary protein C inhibitor. Glycosaminoclycans synthesized by the epithelial kidney cell line TCL-598 enhance its interaction with urokinase

Protein C inhibitor (PCI), also known as plasminogen activator inhibitor 3, inhibits a variety of serine proteases by forming sodium dodecyl sulfate-stable 1:1 complexes. In purified systems PCI is only a weak inhibitor of urokinase. Nevertheless, complexes between PCI and urokinase are found in appreciable amounts in native human urine. Since PCI activity is stimulated by heparin and other glycosaminoglycans, we investigated the presence of stimulating glycosaminoglycans on cells lining the urinary tract. We chose the epithelial kidney tumor cell line TCL-598 as a model and isolated metabolically labeled glycosaminoglycans. TCL-598 incorporated [35S] sulfate into high Mr components (Mr greater than 200,000 and approximately 75,000) as judged from sodium dodecyl sulfate-polyacrylamide gel electrophoresis and autoradiography of cell extracts; the Mr greater than 200,000 component bound specifically to PCI-Sepharose 4B and was eluted either with heparin (5 mg/ml) or with NaCl (2.0 M). Treatment of this PCI-binding material with chondroitinase ABC, but not with chondritinase AC or heparitinase, abolished binding to PCI-Sepharose, confirming the glycosaminoglycan nature of this material and suggesting the involvement of dermatan sulfate in binding. These glycosaminoglycans eluted from PCI-Sepharose stimulated urokinase inhibition by PCI in a dose-dependent way and enhanced complex formation of 125I-urokinase and PCI as did in control experiments dermatan sulfate from porcine skin and from bovine mucosa. Our results suggest that PCI activity might be regulated also in vivo by the presence or absence of stimulating glycosaminoglycans; dermatan sulfate-containing glycosaminoglycans associated with kidney cells might be responsible for stimulation of the urokinase inhibitory activity of PCI in the urinary tract; the type of glucosaminoclycans might furthermore regulate enzyme specificity of PCI.