Local intra-arterial drug delivery for prevention of restenosis: comparison of the efficiency of delivery of different radiopharmaceuticals through a porous catheter

RATIONALE AND OBJECTIVES

Several radiopharmaceuticals were administered through a porous balloon catheter to compare the absolute amount deposited and the retention in the vessel wall. The reported efficiency of local drug delivery ranges from 0.001% to 0.1%, with poor retention after 24 hours.

METHODS

An endothelin derivative (n = 6), pertechnetate (n = 6), hexamethylpropylene amineoxime (HMPAO) (n = 5), ethyl cysteinate dimer (ECD) (n = 5), and tin colloid (n = 5) were labeled with 185 MBq/mL 99m-technetium. After balloon denudation of the infrarenal aorta in 27 New Zealand White rabbits, 100 microL of each agent was administered through a porous balloon at a pressure of 4 bar. Dynamic and static whole-body scintigrams were obtained for 24 hours. The infrarenal aorta was excised and the activity calculated in a gamma counter.

RESULTS

Apart from their retention in the region of local administration, the radiopharmaceuticals showed different distribution patterns. The highest regional tracer retention was observed with HMPAO. After administration of HMPAO, a significant difference between regional (vessel wall plus surrounding tissue: 14.5% of injected dose [ID]/24 hours) and local (vessel wall: 1.8% ID/24 hours) delivery was found. In contrast, ECD was eliminated quickly (local retention after 24 hours = 0% ID). The retention efficiencies were HMPAO > endothelin derivative > tin colloid > pertechnetate > ECD.

CONCLUSIONS

The different physicochemical and pharmacokinetic properties of radiopharmaceuticals resulted in different delivery efficiencies after local application.

The use of gadolinium chelates for X-ray digital subtraction angiography

RATIONALE AND OBJECTIVES

To evaluate the feasibility and safety of using gadolinium chelates for x-ray digital subtraction angiography (DSA) in patients with contraindications to iodinated contrast material.

METHODS

We performed 30 DSAs in 22 patients (5 females, 17 males; mean age 64.9 years) with contraindications to iodinated contrast media (renal insufficiency: n = 28; hyperthyroidism: n = 1; contrast allergy: n = 2). Gadolinium chelates were administered as 0.5 mol/L solutions (mean volume of gadolinium chelates per patient was 34 +/- 19 mL). Gadolinium chelates were the sole contrast agent in 17 examinations, were used in conjunction with carbon dioxide (CO2) in 8 studies, (mean 212 +/- 226 mL), and were combined with the restricted use of nonionic iodinated contrast (mean 12.8 +/- 4.7 mL) in 6 examinations. We carried out 15 diagnostic angiographies and 15 percutaneous transluminal angioplasties.

RESULTS

Use of gadolinium chelates allowed us to obtain diagnostic angiographic images in all cases. However, the quality of angiograms was inferior compared with that obtained with iodinated contrast agents and superior compared with CO2 as the contrast material. Adverse events were not noted. Mean serum creatinine was 2.6 +/- 1.5 mg/dL before and 2.3 +/- 1.0 mg/dL after DSA. No patient developed contrast-induced nephropathy.

CONCLUSIONS

Gadolinium chelates produce an x-ray DSA intermediate in image quality between iodinated contrast and CO2. Digital subtraction angiography with intra-arterial gadolinium chelate administration may offer an alternative to iodinated contrast material in patients with contraindications to iodine.

In vivo evaluation of an intravascular receiver coil for MRI at 1.0 Tesla

BACKGROUND

Evaluation of the applicability of intravascular radiofrequency receiver coils by means of a pig in-vivo-experiment for the detection of vessel wall structures at 1.0 Tesla.

MATERIALS AND METHODS

The intravascular receiver coil was constructed according to a well evaluated single-loop-design, which was mounted onto a balloon catheter for angioplasty. Under fluoroscopy control the balloon catheter was placed in the common carotid artery of a porcine. Images were obtained in a 1.0 Tesla clinical scanner using a fast-spin-echo-, a gradient-echo- and a high resolution spin-echo-sequence. Histological examinations were obtained to detect any vessel wall damage associated with the use of the receiver coil.

RESULTS

High quality images with a resolution up to 0.16*0.12 mm2 could be acquired in aquisition times of about 5 minutes. Subtle intra- and extra-vascular structures such as the balloon, irregularities of the vessel wall or bordering structures could be visualized. The histological examination showed no vessel damage due to the application of the intravascular receiver coil.

CONCLUSIONS

The application of intravascular receiver coils for the visualization of the vessel wall is feasible at 1.0 Tesla without histologically detectable trauma to the vessel wall.

[A review of molecular radiology. I: Gene therapy]

The term molecular radiology intermediate region between radiological imaging and interventional radiology on the one side and molecular biology on the other. In the field of imaging methods are currently being developed by which molecular processes, i.e., gene expression and protein function, can be visualized in vivo. These techniques open new perspectives for research and clinical diagnosis and will be presented in the second part of this review. The present part provides a survey of current developments in gene therapy from a radiological point of view and highlights the part that our specialty may play in this field.

Quantitative human in vivo evaluation of high resolution MRI for vessel wall morphometry after percutaneous transluminal angioplasty

Visualization of the vessel wall after transluminal angioplasty is important to monitor the restenosis progress. Intravascular ultrasound proved its capabilities as an invasive procedure in many studies. The aim of this study was to evaluate the feasibility of high-resolution MRI as a non-invasive tool for follow-up after PTA. High-resolution magnetic resonance images (pixel size: 0.49 * 0.49 mm(2)) were acquired on a 1.0 T clinical scanner. Morphometry was conducted after conversion of DICOM images into TIFF format using ScionImage on a PC. In-vitro studies using a polyvinylchloride tube were evaluated by two independent investigators. Goldstandard was a caliper rule and direct radiography. Five patients were monitored before and 24 h, six weeks, three months and six months after PTA. In vivo measurements promised a good concordance for both investigators for area as well as for diameter measurements. Area measurements showed correlations up to r = 0.86 (p < 0.001) whereas the correlations of diameters were slightly inferior (r between 0.58 and 0.84; p < 0.005). Relocation of the same slice position in the follow up studies could be guaranteed using anatomic landmarks in the images. As a non-invasive tool to assess restenosis after PTA high-resolution MRI promises to be a reproducible technique. It is easy to identify the same vascular region in different studies due to neighboring anatomic landmarks. Progression of disease as well as success of pharmacologic treatment to prevent restenosis may be monitored.

Mid-term follow-up after percutaneous hydrodynamic thrombectomy in lower limb ischemia: initial experience with two-dimensional MR imaging and three-dimensional MR angiography

PURPOSE

To assess noninvasively mid-term patency, reocclusion, and mid-term changes of the arterial wall after percutaneous hydrodynamic thrombectomy in patients with acute lower limb ischemia using magnetic resonance (MR) imaging/MR angiography (MRA).

MATERIALS AND METHODS

Arterial wall and luminal changes were evaluated in 16 patients (10 men, six women; mean age, 70 years), with a minimum follow-up of 12 months after percutaneous thrombectomy with a hydrodynamic catheter for acute lower limb ischemia (embolic, n = 5; thrombotic, n = 11). Adjunctive PTA was performed in 44%. The mean follow-up was 23 months +/- 7.6 (range, 12-33 months). MR imaging and MRA were performed on a 1.0 T system using an extremity coil and two-dimensional (2D) time-of-flight, turbo spin echo, 2D gradient echo, and contrast enhanced three-dimensional (3D) gradient echo sequences.

RESULTS

In one patient, a complete reocclusion was noted and, in two patients, a hemodynamically insignificant restenosis (< or = 50%) was identified with MR imaging. This was in accordance with color flow duplex sonography, physical examination, ankle/brachial index measurements, and the treadmill test. The MR morphometry documented an increase of the entire vessel area from 48.9 mm2 +/- 3.3 (control segments) to 55.5 mm2 +/- 2.8 at the treated segments (+13.3%; P < .05). The vessel wall area increased from 31.7 mm2 +/- 1.8 to 39.4 mm2 +/- 2.3 (+24.4%; P < .05). The mean area stenosis grade was 12%.

CONCLUSION

MR imaging with use of morphometric analysis is a possible tool to noninvasively determine the mid-term patency and restenosis/reocclusion and remodeling process after percutaneous thrombectomy and other interventional procedures.

Prospective comparison of magnetic resonance sialography and digital subtraction sialography

We sought to compare the diagnostic utility of magnetic resonance sialography (MRS) and digital subtraction sialography (DSS) in patients with suspected sialolithiasis or sialadenitis. Sixteen consecutive patients (4 female and 12 male, mean age 51+/-16 years) with suspected sialolithiasis or sialadenitis underwent DSS by a standard technique and MRS. MRS was obtained with a T2-weighted single-shot TSE sequence (TR/TE 2800/1100 msec, acquisition time 7 seconds) using a quadrature head (n = 16) and a surface coil (n = 8). Nineteen symptomatic glands were investigated with DSS: eight submandibular glands in 6 patients (two bilateral) and unilateral parotid glands in 11 patients. MRS was always carried out to visualize gland ducts bilaterally. The ductal system was visualized in all glands examined by MRS. DSS depicted the ductal system in all 11 parotid glands, but only 4 of the 8 submandibular glands (50%). Sialolithiasis was diagnosed in three cases (one parotid, two submandibular glands) by MRS and in two cases by DSS. DSS demonstrated tertiary branching ducts and MRS secondary branching ducts. MRS is able to visualize the ductal system of the parotid and submandibular gland noninvasively and is thus not dependent on successful cannulation of the orifice of the ductal system. Our preliminary data indicate that MRS is useful for diagnosing sialolithiasis. MRS allows diagnosis of sialadenitic changes, but DSS achieves a better diagnostic performance due to higher spatial resolution.

Rheolytic hydrodynamic thrombectomy for percutaneous treatment of acutely occluded infra-aortic native arteries and bypass grafts: midterm follow-up results

RATIONALE AND OBJECTIVES

To evaluate the efficacy of a rheolytic thrombectomy catheter (RTC) for treatment of acutely occluded infra-aortic native arteries and bypass grafts and to determine midterm primary patency, death, and amputation-free survival rates.

METHODS

From March 1995 to September 1997, 112 patients with occluded arteries or bypass grafts were primarily treated with RTC at two centers. Thrombus removal was evaluated by two angiographers.

RESULTS

More than 75% of the thromboembolic material could be removed with RTC alone. Mean activation time of RTC was 280 +/- 163 seconds. Residual mural or organized thrombi (29%) required adjunctive fibrinolytic therapy or aspiration thrombectomy. Remaining stenoses were treated with percutaneous transluminal angioplasty and additional stent implantation. For acute reocclusions, surgical intervention was required. Technical success after the entire procedure was 88.4%. RTC-associated complications included distal embolization, dissection, vessel perforation, and technical failure of RTC. Mean follow-up time was 14.8 months +/- 11.5, rates of primary patency, secondary patency, death, and amputation-free survival were 60%, 84%, 16%, and 75% after 2 years, respectively.

CONCLUSIONS

RTC is a rapid and efficient technique for mechanical thrombectomy of acutely thrombosed native leg arteries and bypass grafts. Midterm results are comparable to the results of alternative treatment modalities such as Fogarty balloon thromboembolectomy or local fibrinolysis.

Cleavage of surfactant-incorporating fibrin by different fibrinolytic agents. Kinetics of lysis and rescue of surface activity

Incorporation of surfactant into polymerizing fibrin causes loss of surface activity and marked retardation of clot lysis by plasmin (Günther and colleagues, Am. J. Physiol. 1994;267:L618-L624). We compared the efficacy of tissue-type plasminogen activator (t-PA), urokinase-type plasminogen activator (u-PA), activated anisoylated streptokinase-plasminogen activator complex (APSAC), and plasmin to dissolve surfactant-incorporating fibrin. Alveofact was employed as a natural surfactant source, and plasminogen was coincorporated into the fibrin matrix at a physiologic ratio to fibrin. Fibrinolysis was quantified by the release of tracer from (125)I-labeled fibrin, and the pattern of split products was characterized by sodium dodecyl sulfate polyacrylamide gel electrophoresis. In addition, we investigated the fibrinolysis-related restoration of surface activity by measurement in the pulsating bubble surfactometer. Concentrations of all fibrinolytic agents were chosen to effect approximately 40% lysis of clot material in the absence of surfactant (control). When incorporated into the fibrin matrix, but not when admixed after clot formation, surfactant inhibited the cleavage of fibrin by all fibrinolytic agents in a dose-dependent manner. Interestingly, t-PA and u-PA were significantly less inhibited than was plasmin or APSAC. The pattern of arising fibrin scission products was identical for all fibrinolytic approaches and was independent of surfactant incorporation. Adsorption and minimum surface tension-lowering properties of Alveofact were almost completely lost upon incorporation into fibrin, but surface activity was fully restored upon sustained clot lysis with all fibrinolytic agents. We conclude that the fibrinolytic capacity of all agents investigated is markedly inhibited by surfactant incorporation in fibrin, but this inhibition is significantly less pronounced in the agents employing preincorporated plasminogen (t-PA and u-PA), as compared with plasmin and APSAC. The plasminogen activators may thus proffer to "rescue" pulmonary surfactant function by induction of fibrinolysis in the alveolar compartment.

FGFR2 signaling in normal and limbless chick limb buds

FGF10 and FGF8, which are reciprocally expressed by the mesoderm and AER of the developing limb bud, have been implicated in limb initiation, outgrowth, and patterning. FGF10 and FGF8 signal through the FGFR2b and FGFR2c alternative splice isoforms, respectively [Ornitz DM, et al. 1996. J Biol Chem 271:15292-15297; Igarashi M, et al. 1998. J Biol Chem 273:13230-13235]. A paracrine signaling loop model has been proposed whereby FGF10 expressed by limb mesoderm signals via ectodermally restricted FGFR2b to regulate FGF8 expression by the apical ectoderm; in turn, FGF8 signals via mesodermally restricted FGFR2c to maintain FGF10 expression [Ohuchi H, et al. 1997. Development 124:2235-2244; Xu X, et al. 1998. Development 125:753-765]. To explore this model, we have examined FGFR2b and FGFR2c mRNA expression, using isoform-specific probes during the early stages of development of the chick limb when limb initiation, AER induction, and outgrowth are occurring. We have found that FGFR2b is expressed by limb ectoderm, including the AER, consistent with paracrine signaling of FGF10. By contrast, FGFR2c is expressed by both mesoderm and ectoderm, indicating that FGF8 has the potential to function in an autocrine as well as paracrine fashion. Indeed, as the limb grows out in response to the AER, FGFR2c expression attenuates in the mesoderm of the progress zone, but is maintained in the AER itself, arguing against exclusive paracrine signaling of FGF8 during limb outgrowth. We also report that transcripts for FGF10, FGFR2b, and FGFR2c are expressed normally in the limb buds of limbless mutant embryos, which fail to form an AER and do not express FGF8. Furthermore, we detect no mutations in exons specific for the FGFR2c or FGFR2b isoforms in limbless embryos. Since gene targeting has shown that expression of FGF8 in limb ectoderm depends on FGF10 [Min H, et al. 1998. Genes Dev 12:3156-3161; Sekine K, et al. 1999. Nature Genet 21:138-141], these results indicate that the product of the limbless gene is required for FGF10 to induce expression of FGF8.

Local administration of ramiprilat is less effective than oral ramipril in preventing restenosis after balloon angioplasty in an animal model

PURPOSE

To test the hypothesis that local administration of angiotensin converting enzyme (ACE) inhibitor via a microporous balloon catheter would be more effective than oral administration of ACE inhibitor in preventing neointima formation after balloon angioplasty.

MATERIALS AND METHODS

Neointima formation was induced by balloon denudation followed by 0.5% cholesterol diet in 29 New Zealand White rabbits. Directly after denudation, local administration of 1.8 mg of ramiprilat (n = 7) or saline (n = 7) with a microporous balloon catheter at a pressure of 3 atm was performed. Both groups additionally received ramipril orally (1 mg/d). Seven animals were treated exclusively with oral ramipril. The control group was fed a 0.5% cholesterol diet and given no medication (n = 8). Six weeks after intervention, the animals were killed and morphometric and immunohistologic analyses were performed.

RESULTS

Oral administration of ramipril resulted in a significant reduction of placque area (-66%, P < .05). Oral and local administration of the ACE inhibitor was followed by a nonsignificant reduction of the neointimal area (-17%). Local administration of saline combined with oral ramipril failed to prevent neointimal formation (reduction of 6%, NS).

CONCLUSION

Oral administration of ramipril resulted in a significant reduction of neointimal proliferation in New Zealand White rabbits. The possible benefit of an additional administration of local ramiprilat was diminished by an excessive neointimal hyperplasia, which was most likely caused by the inherent vessel trauma with use of the microporous balloon catheter.

[Effects of L-carnitine on erythropoiesis and blood platelet aggregation in patients with chronic renal failure treated with hemodialysis]

The aim of the work has to assess the effects of L-carnitine therapy on erythropoiesis and whole blood platelet aggregation. The studies were performed in 28 patients divided into 3 groups: I-group was given erythropoietin, II-group was given erythropoietin and L-carnitine, III-group was given L-carnitine. After 22 month of the therapy a statistically significant rise in hematocrit was observed in group III, improvement in muscle strength, a rise in free and total carnitine concentration was found in group II and III. There were no significant changes in urea concentration, platelet count and iron metabolism. Whole blood platelet aggregation induced by ADP, collagen and ristocetin was impaired relative to healthy volunteers. After 2 month of L-carnitine treatment of significant rise in collagen induced platelet aggregation was observed in group II.

[Intra-arterial application of the ACE inhibitor ramipril using a microperforated catheter for the prevention of neointimal proliferation after angioplasty in an animal model]

PURPOSE

To evaluate the safety and benefit of a high-dose local drug administration via a microporous balloon catheter to prevent neointimal formation after balloon angioplasty.

MATERIALS AND METHODS

In New Zealand white rabbits (n = 29) neointima formation was induced by balloon denudation. Additionally, the animals were fed a 0.5% cholesterol diet for 6 weeks. Directly after the denudation, local application of 1.8 mg ramipril (n = 7) or saline (n = 7) via a microporous balloon catheter was performed. Other animals (n = 7) were treated with a systemic ramipril administration. One control group were exclusively fed with a cholesterol diet (n = 8). 6 weeks after intervention the animals were sacrificed and morphometry of the vessels was performed.

RESULTS

Local administration of ramipril resulted in a non-significant reduction of 17%. The local administration mode was combined with a significant increase in neointima formation. Systemic ramipril administration resulted in a 66% reduction of plaque area.

CONCLUSIONS

The benefit of the local ramipril administration was diminished by the inherent vessel trauma. Systemic ramipril administration resulted in a significant reduction of neointimal proliferation in New Zealand white rabbits.

[Yamakawa prosthesis with prolonged placement as a therapy concept exemplified by benign biliary stricture]

AIM

As an alternative method to the operative revision of benign bile duct strictures, we report the use of a large-bore bile duct prosthesis (Yamakawa prosthesis) in one patient.

METHODS

Bilateral percutaneous transhepatic implantation of Yamakawa prostheses (14 F right side, 12 F left side) was performed without adjunctive balloon dilatation. The prostheses were exchanged every 8 weeks under continuous antibiotic treatment and were finally removed after 8 months.

RESULTS

Control cholangiography showed a normal intrahepatic biliary system on the right side and a 50% stenosis at the orifice of the left hepatic duct. Follow-up over 18 months showed no signs of recurrent disease.

CONCLUSIONS

In comparison to balloon dilatation and implantation of metallic stents, prolonged bilateral splinting with large-bore Yamakawa prostheses seems to be an alternative for the treatment of benign bile duct strictures.

[Plaque morphology after arterial interventions in the New Zealand white rabbit--which model of restenosis is most suitable?]

PURPOSE

For evaluation of therapy for possible reduction of restenosis after PTA a suitable animal model is needed. The influence of different interventions on arterial plaque composition was analysed in New Zealand White Rabbits.

MATERIAL AND METHODS

The following interventions were performed in the infrarenal aorta of New Zealand White Rabbits (n = 42): a) Balloon denudation (BD) with and b) without 0.5% cholesterol diet (CD), c) application of a Wiktor stent, d) CF without BD, and e) control group, 6 weeks after intervention morphometry and histology were performed.

RESULTS

After BD the stenosis rate measured 26 +/- 18%, additional CD after prior BD increased the stenoses rate by 2.5 times up to 61.1%. After stent implantation there was only a thin neointimal layer (89 +/- 68 microns) around the stent wires.

CONCLUSIONS

Neither implantation of stents nor single CD are suitable as restenosis models. BD with and without CD was followed by a distinct neointima formation with different cellular composition. The New Zealand White Rabbit constitutes an acceptable model for contemporary research in arteriosclerosis.

[Use of low-molecular weight heparin during hemodialysis]

Coagulation parameters--platelet aggregation, beta-thromboglobulin, fibrinopeptide A were analyzes in patients with final chronic renal insufficiency during haemodialysis after a low molecular weight heparin application. In the study was documented that standard heparin is able to induce platelet aggregation. A low molecular weight heparin is suggested as sefex, because no influence on platelet aggregation was determined.

Inverse relationships between haemoglobin and ristocetin-induced platelet aggregation in haemodialysis patients under erythropoietin therapy

BACKGROUND

Amelioration of the anaemia of chronic renal failure and subsequent improved haemorheology result in correction of bleeding diathesis as evidenced by shortening of the skin bleeding time (BT). However, the relationship between the haematocrit and platelet-vessel wall interactions in haemodialysis (HD) patients under recombinant human erythropoietin (rHuEpo) therapy, assessed by platelet aggregation in response to ristocetin is more complex and somewhat inconsistent.

METHODS

We investigated the relationship between haemoglobin (Hb) levels and whole blood ristocetin-induced platelet aggregation (electric impedance method) in 28 HD patients treated with rHuEpo, and with normal BT. The measurements were repeated in 16 subjects after having reduced platelet aggregability with orally administered ketanserin.

RESULTS

Ristocetin-induced platelet aggregation in the whole group was comparable to those found in 21 age-matched healthy subjects (normals) and in 25 HD patients not treated with rHuEpo (uraemics). Interestingly, a significant inverse correlation between this aggregation and Hb concentration was found (r = -0.392, P < 0.05). In the group of 16 patients, the pre-ketanserin aggregation was more intensive than in the normals and uraemics (P < 0.05). Ketanserin produced a fall in ristocetin-induced platelet aggregation (P < 0.02), prolongation of the BT (P < 0.02) and, unexpectedly, a decrease in serum Epo concentration (P < 0.0002) and the Hb level (P < 0.001). Again, an inverse correlation between depressed ristocetin-induced platelet aggregation and lowered Hb concentration was found (r = -0.590, P < 0.02). Moreover, a strong positive correlation between the extent of preketanserin platelet aggregation and the decrease in the intensity of this process that followed the trial was observed (r = 0.919, P < 0.000005). There were no changes in other haematological parameters or arterial blood pressure.

CONCLUSIONS

Considering the role of von Willebrand factor and fibrinogen in mediating ristocetin-induced platelet aggregation, and enhanced synthesis and/or release of these macromolecules in response to uraemia or inflammation, we suggest that exaggerated whole-blood platelet aggregability to ristocetin points to blunted erythropoiesis in HD patients on rHuEpo therapy.

[Effect of deferoxamine on erythropoiesis in patients hemodialyzed for chronic renal insufficiency treated with erythropoietin]

The aim of the study was to evaluate the effect of deferoxamine therapy on erythropoiesis, aluminium concentration and iron metabolism in hemodialyzed patients with chronic renal insufficiency treated with human recombinant erythropoietin (Eprex, Cilag). 8 hemodialyzed patients (2 female and 6 male) in long-term programme with aluminium serum concentration over 160 micrograms/l were treated with deferoxamine (5 mg/kg b.m.) during the last hour of hemodialysis in slowly intravenous infusion since 1 months. During this treatment aluminium and iron serum concentrations, serum iron-binding capacity, transferrin and hematocrit were determined before and after 1 months of deferoxamine therapy. The significant decrease of aluminium serum concentration (p < 0.05) and increase of hematocrit (p < 0.01), iron (p < 0.05) and serum iron-binding capacity (p < 0.001) were determined. The results of performed analysis indicate that aluminium is able to inhibit erythropoiesis induced by erythropoietin. The improvement in erythropoiesis and iron metabolism after deferoxamine therapy was observed.

Surfactant incorporation markedly alters mechanical properties of a fibrin clot

Intra-alveolar clot formation is a common finding in acute and chronic inflammatory lung diseases. Incorporation of lipophilic surfactant components into a growing fibrin clot has recently been reported (Am. J. Respir. Cell Mol. Biol. 1993; 9:213-220). In the present study, we investigated the influence of such surfactant incorporation on the elastic properties and water permeability of the fibrin polymer. Thrombelastography and compaction experiments were employed for assessment of the elastic properties, and the permeability characteristics of the clot material were addressed in fibrin-packed columns. Two calf lung surfactant extracts (CLSE and Alveofact), Curosurf, and a synthetic phospholipid mixture (dipalmitoylphosphatidylcholine, phosphatidylglycerol, and palmitic acid at a ratio of 68.5:22.5:9 [wt/wt]) were used. The presence of surfactant did not affect the cleavage of fibrinopeptide A upon incubation of fibrinogen with thrombin (enzyme-linked immunosorbent assay technique). Similarly, kinetics and extent of factor XIII-induced covalent crosslinkage of the fibrin network remained unchanged in the presence of surfactant (sodium dodecyl sulfate polyacrylamide gel electrophoresis and D-Dimer quantification upon subsequent clot lysis). All surfactants, however, dose-dependently decreased the elastic modulus of the arising fibrin polymer. The maximal amplitude in thrombelastography was reduced, and the recovery of fluid after centrifugation of the fibrin clot increased. Fibrin clots embedding natural surfactant material displayed reduced permeability for saline as compared with control fibrin polymers. Subsequent washout of lipids from these clots with Triton X-100 resulted in increased hydraulic conductivity. This was accompanied by an increase in pore size, suggesting altered architecture of the fibrin matrix generated in the presence of surfactant.(ABSTRACT TRUNCATED AT 250 WORDS)

A study of platelet functions, some hemostatic and fibrinolytic parameters in relation to serotonin in hemodialyzed patients under erythropoietin therapy

Erythropoietin corrects anemia and improves hemostasis, but on the other hand bears a risk of thrombotic complications. Therefore in the present study an attempt has been made to evaluate bleeding time, platelet functions and some hemostatic and fibrinolytic parameters in relation to blood and platelet serotonin before and after 1, 2, 4, 8 and 12 weeks of treatment. 22 chronically hemodialyzed patients were administered with human recombinant erythropoietin (rHuEPO) in a dose of 2000 IU s.c. 3 times a week. Bleeding time was shortened significantly as early as after 1 week of the therapy, whereas hematocrit and hemoglobin increased after 2 weeks. These changes lasted throughout the study. Only a transient rise in platelet count, collagen-induced platelet aggregation, beta-thromboglobulin and VIII:C activity were observed during therapy relative to baseline values. ADP- and arachidonic acid-induced platelet aggregation seemed to be unaffected by rHuEPO treatment, whereas a gradual and progressive enhancement in platelet aggregation in response to ristocetin was found, starting from the 2nd week of the therapy. It lasted throughout the study and correlated inversely with the bleeding time and positively with a rise in both blood and platelet serotonin. rHuEPO did not alter plasminogen, fibrinogen, platelet factor 4, alpha 2 macroglobulin levels, protein C activity and euglobulin clot lysis time. A decline in protein C and S concentrations and antithrombin III activity observed during the therapy were counterbalanced by a fall in the activity of alpha 2 antiplasmin, C1 esterase inhibitor and plasminogen activator inhibitor. It is concluded that rHuEPO may improve platelet/vessel wall interactions possibly by means of serotonergic mechanisms. A lowered activity of inhibitors of fibrinolysis may be regarded as a protection against a general tendency to thrombosis during rHuEPO therapy.

Clot-embedded natural surfactant: kinetics of fibrinolysis and surface activity

Polymerization of fibrin in the presence of pulmonary surfactant was recently noted to induce incorporation of phospholipids into the insoluble clot material, thereby effecting severe loss of surface activity (W. Seeger, A. Elssner, A. Günther, H.-J. Krämer, and H. O. Kalinowski. Am. J. Respir. Cell Mol. Biol. 9: 213-220, 1993). In the present study, we investigated the influence of such incorporation of calf lung surfactant extract (CLSE) on the enzymatic cleavage of the fibrin network with the use of plasmin, trypsin, or elastase. Employing a fibrin-plate assay, the proteolytic release of radioactivity originating from 125I-labeled fibrinogen was assessed, and the pattern of split products was characterized by sodium dodecyl sulfate-polyacrylamide gel electrophoresis technique. Surface activity of CLSE was measured in the pulsating bubble surfactometer. When incorporated into the fibrin clot, CLSE inhibited the cleavage of fibrin by all proteases in a dose-dependent manner without affecting the profile of scission products. Inhibition of plasmin-induced clot lysis was also noted on incorporation of CLSE into clotted plasma and on incorporation of dipalmitoylphosphatidylcholine into fibrin polymers. In contrast, corresponding concentrations of CLSE added to the incubation medium after preformation of the fibrin matrix did not substantially influence the kinetics of fibrinolysis. CLSE incorporation into the nascent fibrin clot resulted in complete loss of surface activity, but adsorption and surface tension-lowering properties were largely restored by subsequent plasmic clot lysis. Arising fibrin split products were shown to display similar inhibitory strength on CLSE surface activity compared with fibrinogen split products.(ABSTRACT TRUNCATED AT 250 WORDS)

Dietary selenium intake of preschool children

The results of this investigation indicate that the range of selenium intakes of the preschool children who were studied was in the acceptable range of adequate and safe as suggested by the Food and Nutrition Board. The majority of the selenium in the diets of the subjects came from grains. Although the amount of selenium consumed was within normal limits, the concentration in the diet was estimated to be 70% of the expected value for mixed diets, i.e., 0.1 microgram/gm.

Concentration and subcellular localization of zinc in the hippocampal formation, cerebellum, and whole brain during the postnatal development of the rat

Zinc was determined by means of atomic absorption techniques in the hippocampal formation, the cerebellum, the whole brain, and their subcellular fractions during the postnatal development of rats. Large quantities of zinc were found already in newborn animals. In the whole brain, the zinc amounts increased between the birth and the 15th day of age, whereas in the hippocampal formation and cerebellum the zinc concentration did not change remarkably during the postnatal maturation. The zinc content of the subcellular fractions revealed a shift to the synaptosomes and mitochondria during the postnatal development. No significant difference of zinc amounts was shown between the CA3 and hilus fasciae dentatae region and the whole hippocampal formation. Concluding from the present results there are obvious discrepancies between the quantitative and histochemical data of the zinc distribution in the rat brain.