Stabilisation of crosslinked ultra-high molecular weight polyethylene (UHMW-PE)-acetabular components with alpha-tocopherol.

A stabilisation of crosslinked ultra-high molecular weight polyethylene (UHMW-PE) with alpha-tocopherol (vitamin E) used for endoprostheses can increase its resistance against oxidative degradation remarkably. However, the method used for conventional UHMW-PE of adding alpha-tocopherol to the UHMW-PE powder before processing can not be applied for crosslinked UHMW-PE, since the alpha-tocopherol hinders the crosslinking process, which would be accompanied by a heavy degradation of this vitamin. The alpha-tocopherol has therefore to be added after the crosslinking process. This paper presents two methods for a stabilisation of finished products with alpha-tocopherol. In method 1, UHMW-PE-cubes (20 x 20 x 20 mm3) were stored in pure alpha-tocopherol under inert atmosphere at temperatures from 100 degrees C to 150 degrees C resulting in a high mass fraction of alpha-tocopherol in the edge zones. For further homogenisation, the cubes were stored in inert atmosphere at temperatures from 160 degrees C to 200 degrees C. In method 2, supercritical CO2 was used to incorporate the vitamin into the UHMW-PE. In an autoclave vessel, the cubes were treated with alpha-tocopherol dissolved in supercritical CO2 for several hours at temperatures from 100 degrees C to 170 degrees C. In both cases, the mass fraction of alpha-tocopherol was detected with the help of a FTIR-microscope. Both methods are well suited to stabilise crosslinked UHMW-PE with alpha-tocopherol. A stabilisation of the sensitive edge layer as well as a nearly homogenous distribution with varying alpha-tocopherol content may be realised by varying the process parameters. Using method 2, standard hip cups were stabilized nearly homogeneously with varying mass fraction of alpha-tocopherol. No oxidation of the UHMW-PE could be detected by infrared spectroscopy (FTIR) and HPLC studies showed a very low degradation of the alpha-tocopherol for both processes.

Accelerated ageing experiments with crosslinked and conventional ultra-high molecular weight polyethylene (UHMW-PE) stabilised with alpha-tocopherol for total joint arthroplasty.

Samples of untreated ultra-high molecular weight polyethylene (UHMW-PE), UHMW-PE sterilized with gamma-rays in nitrogen atmosphere (conventional UHMW-PE, widely used for articulating surfaces in endoprostheses) and UHMW-PE, which has been crosslinked by electron beam irradiation and annealed subsequently, were stabilized with alpha-tocopherol and aged in air at 120 degrees C as well as in 10% aqueous hydrogenperoxide with 0.04 mg/ml FeCl3 as catalyst at 50 degrees C. The oxidative degradation was monitored with the help of infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), solubility measurements and size exclusion chromatography (SEC) and were compared to unstabilized samples. When aged in air at 120 degrees C, the crosslinked UHMW-PE showed a slightly slower increase of the carbonyl (CO)-number (according to DIN 53383) in FTIR than conventional UHMW-PE. A stabilisation with 0.4% w/w alpha-tocopherol resulted in an increase of lifetime by a factor of approx. 40 for all samples. Ageing in 10% aqueous H2O2 at 50 degrees C yielded similar results for all three unstabilised samples. The addition of the natural antioxidant alpha-tocopherol led to a prolongation of lifetime by a factor of approx. 2.5. A linear loss of alpha-tocopherol was detected during ageing. An increase of crystallinity as well as lamella thickness during ageing was observed with the help of DSC. The two-phase structure of crosslinked UHMW-PE with two melting endotherms at 114 degrees C and 137 degrees C was replaced very quickly by a single melting point at 130 degrees C. This effect was delayed with the stabilized samples. In the solubility and SEC measurements, a severe molecular degradation and drop of molar mass of all materials could be observed after ageing in H2O2, leading to a complete destruction and, in case of crosslinked UHMW-PE, to a serious damage of the molecular network, respectively.

Animal experiments with ultra-high molecular weight polyethylene (UHMW-PE) stabilised with alpha-tocopherol used for articulating surfaces in joint endoprostheses.

Numerous investigations proved the impressive suitability of alpha-tocopherol as a stabilizer for ultra-high molecular weight polyethylene (UHMW-PE) used for endoprostheses. Regarding the biocompatibility of this new biomaterial, in-vitro celltoxicity tests gave no hint for a cyto- or genotoxic activity. In this study, animal experiments are carried out to further ensure the biocompatibility of this biomaterial. Thin UHMW-PE-films (20 x 6 x 0.23 mm3) were implanted subcutaneously into rats. Morphology and reactivity of surrounding connective tissue against either pure UHMW-PE material or UHMW-PE containing alpha-tocopherol were studied at timed intervals (2 weeks, 3 month, and 6 month after operation) in 3 groups of animals, each group comprising 10 animals. Parallel to these tests, material changes were investigated in these 3 groups of 10 animals at the same intervals after operation with the help of infrared spectroscopy (FTIR). Within the implantation time, no noteworthy oxidative degradation could be observed. The amount of lost alpha-tocopherol due to diffusion is low enough to ensure a lifetime stabilisation of the UHMW-PE. The implants were all well tolerated and definitely encapsulated already 2 weeks after operation. Presence or absence of alpha-tocopherol in the implants did not evince morphological differences. Therefore, negative consequences were not manifest in the presence of alpha-tocopherol.

Concurrent low-dose cisplatin and thoracic radiotherapy in patients with inoperable stage III non-small cell lung cancer: a phase II trial with special reference to the hemoglobin level as prognostic parameter.

PURPOSE: To evaluate the efficacy of concurrent radiochemotherapy in patients with stage III non-small cell lung cancer (NSCLC), and to examine the effect of hemoglobin levels on survival of those patients. The negative impact of anemia on survival has been noticed for other cancer sites including the head and neck, and the uterine cervix, but it has been rarely described in NSCLC cancer patients treated with radiotherapy. METHODS: From April 1995 through March 2002, 56 patients with inoperable stage III non-small lung cancer were treated with radiotherapy consisting of 60 Gy (50 Gy+10 Gy boost) given in 30 fractions of 2 Gy daily, 5 days a week, over a period of 6 weeks, and concurrent low-dose daily chemotherapy (CHT) consisting of 6 mg/m(2) of cisplatin given Mondays-Fridays during weeks 1-2 and 5-6. All patients had stage III disease and ages ranged from 39 to 81 years old (median 63.9 years). RESULTS: The 2-year and 3-year survival rates were 34% and 16%, respectively. Patients with a pretreatment hemoglobin level superior or equal to 11.6 g/dl had a 2-year survival rate of 52% as compared to 15.5% for patients with a pretreatment hemoglobin level inferior to 11.6 g/dl (p=0.0075). Patients with higher KI (>70%) showed better survival rates than those with lower KI. Surprisingly, patients in stage IIIA did not survive significantly longer than those in stage IIIB. Hematological toxicity (grade > or =2) prevailed (25%), followed by esophageal (5.4%) and bronchopulmonary (2%) toxicity. Only three patients experienced acute grade 3 hematological toxicity. Because of acute toxic effects, irradiation was interrupted in 8 patients (14.3%) for 7-13 days (median 7.5 days). Late high-grade (> or =3) toxicity was not found. No grade 4 toxicity or treatment-related deaths were observed during this study. CONCLUSION: Our data show that concurrent radiotherapy with daily low dose cisplatin is well tolerated, and shows survival rates comparable to more aggressive treatment regimens. A combination of this chemotherapy with accelerated hyperfractionated radiotherapy might improve the results in the future. Furthermore, we could show that the hemoglobin levels prior to therapy have an influence on the prognosis, where lower levels were associated with worse outcome. Further trials should consider supplementation with erythropoietin.

Studies on the effect of electron beam radiation on the molecular structure of ultra-high molecular weight polyethylene under the influence of alpha-tocopherol with respect to its application in medical implants.

Ultra-high molecular weight polyethylene (UHMW-PE) is being used successfully for articulating surfaces in joint endoprostheses, especially for cups of total hip endoprostheses. Sintered specimens containing various amounts of alpha-tocopherol (vitamin E) as a biocompatible stabilizer, were irradiated in nitrogen atmosphere as well as in air with various dosages of electron beam radiation. Size exclusion chromatography (SEC) was used to analyze the soluble fractions of the UHMW-PE samples according to their molecular weight distribution prior to and after irradiation. In nitrogen atmosphere the radiation-induced crosslinking showed to be dependent on the added amount of alpha-tocopherol in the sintered specimens. With an increasing content of alpha-tocopherol, the stabilizer acted as a scavenger for free radicals. Thus, the crosslinking was more and more hindered. The same effect was observed on the samples irradiated in air, where, in addition to the crosslinking process, oxidative molecular degradation occurred. The highest extent of crosslinked material was yielded with unstabilized samples in nitrogen atmosphere.

Tests of biocompatibility of alpha-tocopherol with respect to the use as a stabilizer in ultrahigh molecular weight polyethylene for articulating surfaces in joint endoprostheses.

To inhibit the oxidation in vivo of hip-cups made of ultrahigh molecular weight polyethylene (UHMW-PE), the natural antioxidant alpha-tocopherol was added to the polymer. The added alpha-tocopherol may however undergo chemical transformations during manufacturing and sterilization by gamma-irradiation of hip-cups which may differ from human metabolism. Therefore, the question of the biocompatibility of the respective transformation products was investigated on test samples, which were prepared under the same conditions as applied for the production and sterilization of hip-cups. Thin plates (25 x 18 x 2 mm(3)) were fabricated out of test samples to investigate the cytotoxic activity according to EN 30993-5. In cytotoxicity testing, proliferation, mitochondrial activity and membrane integrity were not influenced by the material. In contrast, cell adhesion and cell spreading were diminished as shown with hemalum staining. In order to investigate the genotoxicity, the alpha-tocopherol and its transformation products were extracted from test specimens by n-heptane at 185 degrees C under nitrogen atmosphere. Then the n-heptane was evaporated in vacuo and the remaining alpha-tocopherol and its transformation products were dissolved in DMSO. The genotoxicity of this extract was then tested by the Ames-test according to DIN UA 12 (1995), which showed no indication for genotoxic activity.

Examination of the suitability of alpha-tocopherol as a stabilizer for ultra-high molecular weight polyethylene used for articulating surfaces in joint endoprostheses.

The lifetime of articulating surfaces in joint endoprostheses made of ultra-high molecular weight polyethylene (UHMW-PE), especially of UHMW-PE-cups of hip-endoprostheses, is usually limited to 10-15 years due to material failure as a result of oxidation of the UHMW-PE in vivo. In this study the suitability of the natural antioxidant alpha-tocopherol (vitamin E) as a stabilizer for UHMW-PE in these applications was investigated. Specimens with 0.1%, 0.2%, 0.4% and 0.8% w/w alpha-tocopherol as well as unstabilized samples were sintered and sterilized with gamma-rays at 25 kGy in accordance with standard processing methods of cups for total hip-endoprostheses. These specimens were aged in pure oxygen at 70 degrees C and 5 bar as well as in aqueous H2O2 at 50 degrees C. The degree of oxidation was observed by means of FTIR-spectroscopy, DSC analysis and mechanical testing. The FTIR-measurements showed that alpha-tocopherol can prolong the lifetime of UHMW-PE in an oxidative environment by a factor of more than 2.5. In the mechanical tests no embrittlement could be observed with the stabilized samples. A comparison with the standard antioxidant system Irganox 1010/Irgafos 168 (Ciba-Geigy, Switzerland) was carried out and revealed that alpha-tocopherol can even exceed the stabilization effect of this widely-used antioxidant system.

Crystalline self-assembly into monolayers of folded oligomers at the air-water interface

Insertion of the 1,3-bis(ethynylene)benzene unit as a rigid spacer into a linear alkyl chain, thus separating the two resulting stems by 9 A. induces chain folding at the air-water interface. These folded molecules self-assemble into crystalline monolayers at this interface, with the plane of the folding unit almost perpendicular to the water surface, as determined by synchrotron grazing-incidence X-ray diffraction. Three distinct molecular shapes, of the types U, inverted U, and M, were obtained in the two-dimensional crystalline state, depending upon the number of spacer units, and the number and position of the hydrophilic groups in the molecule. The molecules form ribbons with a higher crystal coherence in the direction of stacking between the molecular ribbons, and a lower coherence along the ribbon direction. A similar molecule, but with a spacer unit that imposes a 5 A separation between alkyl chains, yields the conventional herringbone arrangement.

Proliferative and steroidogenic capabilities of rat granulosa cells of different sizes.

Equine chorionic gonadotrophin stimulates both rat granulosa cell mitoses and oestradiol secretion. However, the mitotic potential of oestradiol-secreting granulosa cells is not known. In the first study, granulosa cells of different sizes were isolated and their ability to secrete oestradiol and proliferate in vitro was determined. Granulosa cells were harvested from equine chorionic gonadotrophin-primed immature rats, separated on a 15-45% Percoll gradient, and collected in 12 fractions. An enriched population of small granulosa cells (44 +/- 1 micron2) was collected in fractions 3 and 4 and an enriched population of large granulosa cells (97 +/- 2 microns2) in fractions 6-8. When granulosa cells from each fraction were cultured for 24 h in the presence of testosterone, the large cells secreted 50% more oestradiol than did the small cells (P < 0.05). Aromatase was shown, by immunocytochemistry, to be expressed mainly by granulosa cells larger than 73 microns2, with the relative amount of aromatase expressed per cell increasing with increasing cell size. However, not all large granulosa cells expressed aromatase. To test proliferative capacity, cells from each fraction were cultured with testosterone and the mitogen, insulin. This study showed that only small cells were able to undergo insulin-induced mitosis. In a second study, follicles of different sizes were isolated from immature and equine chorionic gonadotrophin-primed immature rats and the granulosa cell size distribution determined for each follicle size. This study confirmed that equine chorionic gonadotrophin altered the size distribution from principally small mitotically competent cells to large oestradiol-secreting cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Elevated first-trimester serum relaxin concentrations in pregnant women following ovarian stimulation predict prematurity risk and preterm delivery.

OBJECTIVE: To determine whether ovarian stimulation would result in higher circulating relaxin concentrations and whether this hyperrelaxinemia would be associated with prematurity. METHODS: Two groups of women were studied: 1) women achieving pregnancy after ovarian stimulation (n = 114) and 2) women achieving pregnancy without treatment (n = 37). Serum was obtained at 6-12 weeks' gestational age; fetal number was determined by transvaginal ultrasound. Prematurity risk or preterm delivery was determined from the obstetric record. A specific human relaxin enzyme-linked immunosorbent assay was used to measure serum relaxin concentrations. Hyperrelaxinemia was defined as levels greater than 3 standard deviations above the weighted mean of levels in normal unstimulated singleton pregnancies at 6-12 weeks' gestation. RESULTS: An association was found between prematurity risk or premature delivery and peripheral relaxin concentrations during weeks 6-12 of pregnancy in women having ovarian stimulation and in women having multiple gestations. Circulating relaxin concentrations greater than 16 ng/mL in women having ovarian stimulation and levels greater than 7 ng/mL in women who had multiple gestations predicted prematurity risk or premature delivery in 50% of the women. CONCLUSIONS: These data demonstrate that after ovarian stimulation, some women have highly elevated circulating first-trimester relaxin concentrations. First-trimester hyperrelaxinemia identifies a group of women at risk for prematurity who can be monitored aggressively.

[Sonographic findings following laparoscopic cholecystectomy]. / Sonographische Befunde nach laparoskopischer Cholezystektomie.

In a prospective study 500 patients were examined sonographically following laparoscopic cholecystectomy, 183 on several occasions. In the majority of patients (79.4%) there were no remarkable findings, either clinically or sonographically. In 102 patients (20.4%) there were sonographic abnormalities such as fluid collections in the gallbladder bed (13%), postoperative dilatation of the biliary passages (9.4%), free abdominal fluid (2%) or pleural effusions (1.2%). Only 25 patients (5%) showed clinical symptoms; there was complete agreement with the findings on ultrasound.

Transcervical tubal cannulation and salpingoscopy in the treatment of tubal infertility.

Transcervical tubal cannulation and salpingoscopy are two recent techniques used for the evaluation of tubal patency and pathology. Selective tubal cannulation cannot determine the nature of the obstructive process, although it does allow for the demonstration of potential tubal patency. This may be important in deciding whether therapies requiring tubal patency may be used in specific clinical situations. Because currently there are no controlled studies in the literature evaluating this technique, the therapeutic value of the procedure must be considered unproven at this time. Salpingoscopy gives more detailed information concerning the tubal mucosa. The identification of specific tubal lesions has been described with this modality. The predictive value of salpingoscopy in cases of severe anatomic distortion, ie, fibrous obliteration, seems obvious. However, its predictive value in the presence of more subtle lesions needs to be studied further because its role as a therapeutic modality is as yet undefined.

Extraction of difficult gallbladders by laparoscopic cholecystectomy: development of a new retrieval system.

The retrieval of elusive or torn gallbladders or of those with large stones and lost calculi is often difficult and time-consuming. We developed an extractor to recover these difficult gallbladders and have already used this extraction method successfully in 26 patients.

Mediterranean spotted fever in an American woman.

Mediterranean spotted fever is common in southern Europe, the Middle East, and North Africa, but is unknown in the United States. It has a clinical picture resembling Rocky Mountain spotted fever, but it is a milder disease. We report a case of Mediterranean spotted fever in a young American woman returning from Morocco and review the clinical picture of this disease.

Studies on hydroxyethyl starch. Part I: Molecular characterization by size exclusion chromatography coupled with low-angle laser light scattering.

Two commercially available hydroxyethyl starch (HES) preparations (in clinical use as plasma expanders) specified with Mw = 450,000/MS = 0.7 and Mw = 200,000/MS = 0.5, respectively, and three experimental HES-samples (supposingly similar to the commercial product with the specification 450,000/0.7, except of one with MS = 0.5) were studied. The latter were prepared via acid or enzymatic hydrolysis of waxy-maize starch. Each of the samples was characterized by its intrinsic viscosity and molar substitution, and was studied with low-angle laser light scattering (LALLS) and with size exclusion chromatography (SEC) coupled with LALLS. The weight-average molecular weight Mw of the commercial samples was found to be 60-80% higher than the value given in the product declaration. This discrepancy can be explained by the argument that previous measurements were not carried out at sufficiently small scattering angles to enable reliable extrapolation to zero angle. The calibration functions Mw(v) of the individual HES-samples measured by SEC/LALLS-coupling are identical over a broad range of the elution volume v and are used for calibration of conventional SEC in a subsequent paper. The small, but detectable differences in the Mw(v)-functions indicate interesting differences between these HES-preparations with respect to the effective hydrodynamic density of the branched HES-molecules.

The shape of the fibrinogen molecule: sausage or banana?

The experimental results and the interpretation of small angle X-ray scattering measurements by the author and Hammel (1975) and of small angle neutron scattering measurements by Marguerie and Stuhrmann (1976) on dilute solutions of bovine fibrinogen are compared. The potential of both methods to discern straight and bent cylindrical structures is demonstrated. The study arrives at the conclusion that the question whether the fibrinogen molecule resembles more a banana or a straight sausage cannot be safely decided by the available data. This justifies the previous suggestion of the author to imagine the fibrinogen molecule as a swollen sausage 450 A long and 90 A thick with conceivable flexibility, a molecular model of sufficient universality to include the banana-shaped model of Marguerie and Stuhrmann (1976) as a special case.