Adaptive Radiotherapy Guided by PET/CT in Patients with Locally Advanced Non-Small Cell Lung Cancer: A Phase II Randomized Study

PURPOSE/OBJECTIVE(S)

The aim of this study was to determine whether adaptive radiotherapy guided by functional imaging with flourine-18 fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) can improve local tumor control in patients with locally advanced non-small cell lung cancer (LA-NSCLC).

MATERIALS/METHODS

This was a phase II randomized study comparing the efficacy and safety between PET-guided adaptive radiotherapy and conventional radiotherapy. The primary end point was 2-year local-regional tumor control (LRTC) rate. Secondary end points included local-regional progression-free survival (LR-PFS), progression-free survival (PFS), overall survival (OS), and radiation-related toxicities.

RESULTS

Between November 2012 and June 2017, 72 patients were 1:1 randomized to adaptive and conventional arms. The 2- and 5-year LRTC rates were 63.2% and 58.0% versus 43.0% and 37.6% (P = 0.035) in the adaptive and conventional arms, respectively. The median LR-PFS (14.3 versus 12.0 months; P = 0.010) and PFS (12.8 versus 8.9 months; P = 0.034) were significantly longer in the adaptive arm than in the conventional arm. The median OS was 36.3 months in the adaptive arm and 28.8 months in the conventional arm (P = 0.266). The esophageal volume of receiving ≥60 Gy (V60) in the adaptive arm was lower than that in the conventional arm (P = 0.011), while the V30 for the heart in the adaptive arm was lower than that in the conventional arm (P = 0.077). Other radiological metrological parameters of tumor, organs at risk, and the incidence of ≥grade 2 radiation-related toxicities were not significantly different between the 2 arms.

CONCLUSION

Compared with conventional radiotherapy, PET-guided adaptive radiotherapy significantly improved the 2-year LRTC rate, LR-PFS, and PFS without increased risks of radiation-related toxicities in patients with LA-NSCLC.

Abstract P1-09-06: Gene-set enrichment analysis (GSEA) of breast tissue from healthy women with less than six months history of breastfeeding shows enrichment in Hedgehog signaling, notch signaling and luminal progenitor gene signatures

Introduction: Multiple epidemiological studies have shown that prolonged breastfeeding is associated with a reduced risk of developing triple negative/basal-like breast cancer (TN/BLBC). We have modeled abrupt involution (AI) due to lack of breastfeeding and gradual involution (GI) of the mammary gland that occurs over time upon prolonged breastfeeding in wild-type FVB/N mice and discovered prominent histological and molecular changes in the AI glands over time. Our studies revealed for the first time a clear and persistent expansion of mammary luminal progenitor (LP) epithelial cells in AI glands (AACR abstract#2242, 2018). Here, we corroborate animal studies using normal human breast tissue obtained from a reduction mammoplasty tissue collection study (OSU-2011C0094).

Methods: Breast tissue obtained from parous premenopausal women with no history of breast cancer who breastfed for ≥6 months (GI, n=16) versus those who breastfed for <6 months (AI, n=16) (OSU-2011C0094) was used for gene expression analysis. RNA isolated from these normal mammary tissues was analyzed using Affymatrix Gene ChIP Human Transcriptome array 2.0; Gene Set Enrichment Analysis (GSEA) was used to analyze the microarray data. Molecular Signatures Database was used in GSEA querying C2 curated gene sets, Hallmark gene sets, and Lim-Mammary-Luminal-Progenitor gene sets. H&E sections of the breast tissue were used to assess lobular type by counting number of ductules per terminal ductal lobular unit (TDLU). False discovery rate (FDR) q-values and p-values were used for multiple comparison adjustment.

Results: GSEA revealed that breast tissue obtained from women in the AI cohort exhibited strong positive enrichment for Notch and Hedgehog Signaling (Hhg) pathways (FDR q-value= 0.20 and 0.12, respectively). In GI women, GSEA showed an overall trend towards enrichment in metabolic pathways and immune system functions. Moreover, there was non-significant trend towards positive enrichment of mouse LP gene signature in AI women only (FDR q-value= 0.30). Age and BMI were not statistically different between AI and GI cohorts. Analysis of TDLU, the primary anatomical source of most breast cancers, revealed that breast tissue from AI women had proportionally higher lobular type 1 only epithelium than GI women who exhibited more differentiated lobular epithelium (p-value= 0.049).

Conclusion: We report here for the first time that mammary glands from women who breastfed <6 months were enriched for stem-cell signaling pathways and LP gene signature. This reflects some similarity to BRCA1 mutation carriers, who demonstrate expanded luminal progenitor population. In addition, higher Type 1 TDLU's are seen in breast tissue from parous women who breastfed <6 months. Together, these data demonstrate features for TN/BLBC precursors enriched in patients who breastfed for <6 months. Understanding this mechanistic link will help in developing prevention strategies, particularly for African-American women who have lower prevalence of breastfeeding and higher incidence of TN/BLBC.

Citation Format: Basree MM, Shinde N, Palettas M, Weng D, Stover DG, Sizemore GM, Shields P, Majumder S, Ramaswamy B. Gene-set enrichment analysis (GSEA) of breast tissue from healthy women with less than six months history of breastfeeding shows enrichment in Hedgehog signaling, notch signaling and luminal progenitor gene signatures [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P1-09-06.

Platelet Deposition Induced by Severely Damaged Vessel Wall Is Inhibited by a Boroarginine Synthetic Peptide with Antithrombin Activity

Thrombin plays a key role in platelet activation and thrombosis. Specific inhibition of thrombin appears to be one of the best approaches to prevent thrombus formation. We have studied the effects of a synthetic a-aminoboronic acid derivative - [Ac, (D) Phe-Pro-Boro-Arg-Hydrocloric acid] - on platelet deposition on severely damaged arterial wall. Platelet deposition was evaluated under well characterized rheological conditions in an original perfusion chamber and detected by autologous mIn-labeled platelets. The study was performed “in vivo” in a porcine model of arterial thrombosis triggered by severely damaged vessel wall at blood flow conditions mimicking mild stenosis (1690 s−1) and patent (212 s−1) vessels. In addition, ex-vivo platelet aggregation activity was evaluated by whole blood impedance aggregometry using collagen, ADP and thrombin as agonists. The synthetic a-aminoboronic peptide was intravenously administered as a bolus followed by continuous infusion. Ex vivo thrombin-induced whole blood platelet aggregation was totally abolished, while ADP- and Collagen-induced whole blood platelet aggregation was not modified. The effects of the synthetic antithrombin on platelet deposition were evaluated in native blood (non-anticoagulated) conditions and in combination with heparin. Under both experimental conditions, the synthetic peptide significantly inhibited platelet deposition at local flow conditions of both high (1690 s−1) and low (212s−1) shear rates. Our results suggest that specific inhibition of locally generated thrombin might be a good strategy to prevent platelet dependent arterial thrombus formation independently of the local flow shear rate of the area at risk.

Stratification of Fullerenes

Dodecylated C60 {(Do)nC60(H)n} and butylated C60 {(Bu)nC60(H)n} were synthesized. Spectroscopic and thermal methods, mass spectrometry, XPD, have been employed to characterize the products. X-ray Powder Diffraction (XPD) results reveal that the facecentered- cubic (fcc) structure of C60 expands to a primitive hexagonal structure upon butylation and to a layered structure upon dodecylation. Butylated C60 diffraction pattern has been indexed as a primitive hexagonal structure with ao = 11.5 angstroms and axial ratio = 1.169. The dodecylated C60 also shows sidechain melting behavior with a transition temperature of around 25°C. The paraffinic crystals are produced by the interdigitation of the sidechains. Butylated C60 does not show any sidechain melting.

BRCA mutation status and risk of secondary malignancy following chemotherapy for breast cancer

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Background: Since the BRCA gene is responsible for excisional DNA repair, we hypothesized that breast cancer patients with BRCA mutation would be more susceptible to the induction of second malignancies following chemotherapy treatment than breast cancer patients who tested negative for BRCA mutations. Methods: Breast cancer patients tested for BRCA1 and BRCA2 mutations at the Cleveland Clinic were identified and evaluated for history of neoadjuvant or adjuvant chemotherapy and for the occurrence of subsequent non-breast primary invasive cancer. Patients with inadequate follow-up and those with inoperable disease at diagnosis were excluded from the analysis. Fisher’s exact test was used to compare different cohorts. The IRB at Cleveland Clinic approved the study. Results: Of 115 identified breast cancer patients tested for BRCA mutations, 77 met the inclusion criteria. Twenty-seven of these patients carried BRCA1 or BRCA2 mutations and 50 tested negative for these mutations. Twelve patients (44%) in the BRCA positive group and 8 patients (16%) in the BRCA negative group underwent prophylactic oophorectomy. Median follow-up for the two groups was 53.5 months (75 months in the BRCA positive group and 48.5 months in the BRCA negative group). Median age at diagnosis was 42 years (40.5 years in the BRCA positive group and 44.5 in the BRCA negative group). In the BRCA positive group 3 of 25 patients (12%) treated with chemotherapy developed second malignancies (ovarian cancer, transitional cell cancer in urinary tract and renal cell carcinoma) compared with none of the 2 patients who did not get chemotherapy (p= 1.0). In the BRCA negative group, 2/34 patients (6%), treated with chemotherapy developed second cancers compared with 2/16 patients (12%), who were not treated with chemotherapy (p=0.58). Cancers in the BRCA negative group included two bladder carcinomas in the chemotherapy treated patients and in the non-chemotherapy group, non-small cell lung cancer, uterine, ovarian, endometrial and peritoneal cancers. Conclusions: At more than 4-years of follow up, chemotherapy in operable breast cancer patients was not associated with an increase in the risk of secondary malignancy or with a differential effect on this endpoint by BRCA mutation status in this retrospective study.

No significant financial relationships to disclose.

Therapeutic radiation for breast cancer in BRCA mutation carriers and contralateral breast cancer (CBC) risk

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Background: BRCA mutation carriers diagnosed with breast cancer are at high risk for contralateral second primary breast cancers. Mutations in BRCA1 and BRCA2 lead to defects in DNA repair. Radiation treatment for breast cancer is felt to increase risk of CBC, but the interaction between BRCA status and local radiation therapy with respect to their effects on CBC is unclear. Methods: Through an IRB approved database registry at the Cleveland Clinic, breast cancer patients tested for BRCA1 and BRCA2 mutations were identified and evaluated for CBC events and radiation treatment history. Patients with inadequate clinical follow-up, those with bilateral synchronous breast cancer and those undergoing bilateral mastectomy within one year of the original breast cancer diagnosis were excluded from the analysis. Chi-square test was used to compare CBC rates with or without prior radiation separately in patients testing positive and those testing negative for BRCA mutations. Results: Of 115 identified breast cancer patients tested for BRCA mutations, 57 met the inclusion criteria. Twenty-one carried BRCA1 or BRCA2 mutations and 36 tested negative for these mutations. Median follow-up for the two groups was 69.5 months (92 months in BRCA positive group and 51.5 months in BRCA negative group). Median age at diagnosis was 45 years (41 years in BRCA positive group and 48.5 in BRCA negative group). Among the 21 carriers, 9 patients (43%) developed CBC while only 3 of 36 patients (8%) testing negative for BRCA mutations developed CBC. Thirteen of 21 mutation carriers (62%) had received radiation treatment for the original cancer: CBC occurred in 3 of 13 (23%) radiated patients and 6 of 8 (75%) patients who had not received radiation (p= 0.02). Among 36 patients with negative BRCA testing, 30 (83%) had received radiation: CBC occurred in 3 of 30 (10%) mutation negative patients who had received prior radiation and in 0 of the 6 patients who had not received radiation (p = 0.42). Conclusions: CBC incidence was higher among BRCA mutation carriers than a control group suspected of having hereditary breast cancer but testing negative for these mutations. The use of radiation in the presence of a BRCA mutation, however, does not appear to further increase the risk for CBC.

No significant financial relationships to disclose.

Contribution of the periosteum to bone formation in guided bone regeneration. A study in monkeys

The periosteum has been referred to as a protective barrier in the regeneration of bone defects. The objective of this study was to determine the contribution of periosteum as a natural barrier to bone formation in guided bone regeneration. Mucoperiosteal flaps were elevated bilaterally on the buccal aspect of the mandibular angle in 5 cynomolgus monkeys. Bleeding was induced by perforating the cortical bone. A hemispherical titanium mesh was fixed over the areas thus creating a void 5 mm in height between the mesh and the bone surface. One one side the mesh was covered with an ePTFE membrane (test side). The contralateral side did not receive further treatment (control side). After 4 month healing, histomorphometric analyses were used to determine the percentage of new bone in the void underneath the mesh, and the ratio between mineralized tissue and marrow spaces in new and old bone. The mean percentage of new bone tissue was 77.2 +/- 7.5% for the test sides and 68.6 +/- 8.4% for the control sides (P = 0.018, t-test). This new bone contained 80.0 +/- 3.6% mineralized tissue in the test group and 82.5 +/- 5.0% in the control group (P > 0.05, t-test). In both groups the newly formed bone exhibited significantly less mineralized tissue than the old bone (P < 0.05, t-test). It is concluded from this study that new bone formation was enhanced by the additional use of an ePTFE membrane under a periosteum-lined mucoperiosteal flap when space maintenance was excluded as a critical factor.

Comparison of bioabsorbable and non-resorbable membranes in the treatment of dehiscence-type defects. A histomorphometric study in dogs

BACKGROUND

The goal of this investigation was to compare, histologically and histometrically, the healing process of dehiscence-type defects treated by guided tissue regeneration (GTR) with bioabsorbable polylactic acid (PLA) membranes and non-resorbable expanded polytetrafluoroethylene (ePTF) membranes.

METHODS

Six mongrel dogs were used. Buccal osseous dehiscences were surgically created on the distal roots of the mandibular third and fourth premolars. The defects were exposed to plaque accumulation for 3 months. After this period, the defects were randomly assigned to one of the treatments: GTR with bioabsorbable membrane (PLA), GTR with non-resorbable membrane (ePTFE), open flap debridement (OFD), and non-treated control (NTC). After 3 months of healing, the dogs were sacrificed and the blocks were processed. The histometric parameters evaluated included: gingival recession, epithelial length, connective tissue adaptation, new cementum, and new bone area.

RESULTS

A superior length of new cementum was observed in the sites treated by GTR, regardless of the type of barrier used, in comparison with OFD (P <0.05). No statistically significant differences were found between PLA and ePTFE in any of the parameters with the exception of bone area. PLA presented a greater bone area when compared to ePTFE, OFD, and NTC (P <0.05).

CONCLUSIONS

Within the limits of this study, it can be concluded that both barriers are equally effective for new cementum formation. The bioabsorbable membrane may provide a greater bone area than the non-resorbable membrane.

A single-incision technique to harvest subepithelial connective tissue grafts from the palate

This article describes a new and simplified surgical approach to harvest subepithelial connective tissue grafts from the palate. For this procedure, only a single incision parallel to the gingival margin is used to access the donor site for graft preparation and harvesting. Grafts of variable size and thickness can be obtained. Since no band of epithelium is removed with the connective tissue graft the palatal donor site can heal with primary intention. No stents or hemostatic agents are necessary to cover the donor area postoperatively, and suturing can be reduced to a minimum. The harvesting technique is illustrated step by step, and the clinical application of connective tissue grafts harvested with the proposed method is demonstrated with the coverage of a gingival recession.

Functional and esthetic outcome enhancement of periodontal surgery by application of plastic surgery principles

The closure of surgical wounds in a layer-by-layer fashion, a common principle of plastic surgery, is applied in this article to the field of periodontal surgery with the introduction of a new flap design. The suggested technique is indicated with all periodontal procedures that aim for hard and soft tissue augmentation (guided bone regeneration, mucogingival surgery, or plastic periodontal surgery) where passive, tension-free wound closure is fundamental for wound healing and a successful functional and esthetic outcome. By means of a series of incisions, buccal and lingual flaps are split several times; this results in a double-partial thickness flap and a coronally positioned palatal sliding flap, respectively. Thus, several tissue layers are obtained and the passive advancement of flaps becomes possible for the coverage of augmented areas. Wound closure with microsurgical suture material is accomplished in a multilayer approach, which ensures adaptation and closure of the outer tissue layers without any tension. Two case reports demonstrate the new plastic periodontal approach.

Identification of elf1, a beta-spectrin, in early mouse liver development

Beta-spectrins play essential roles in cell-cell interactions and in the maintenance of cell polarity. Our aim was to identify beta-spectrin genes important for the establishment of hepatocyte polarity and differentiation. Using subtractive screening of cDNA libraries from early embryonic mouse livers (post-coital days 10, 11, and 12), we have isolated elf1 (embryonic liver fodrin 1), a differentially expressed beta-spectrin or fodrin (betaSpIIsigmaI). Elf1 encodes a 220-amino acid protein with an NH2 terminal actin-binding domain. In situ hybridization studies demonstrate elf1 expression initially in day 10 embryonic heart tissue, then in day 11-11.5 hepatic tissue. These studies suggest that elf1 may play a role in the emergence of hepatocyte polarity during liver development.

Healing patterns in recession defects treated with ePTFE membranes and with free connective tissue grafts. A histologic and histometric study in the beagle dog

This study focussed on the biologic success of 2 different procedures for root coverage. In the maxillary canines of 7 beagle dogs, buccal recessions were created and treated on one side with an ePTFE membrane (GTR-group) and on the contralateral side with a free connective tissue graft from the palate (CT-group). 2 areas served as negative controls. After 4 months of healing, histologic sections were processed and histologically analyzed. The evaluated parameters were coverage height, bone, cementum and connective tissue attachment regeneration, length of the epithelium, resorption, and ankylosis. Histologically, both GTR-group and CT-group produced more new bone, new cementum and new connective tissue attachment than the two control teeth. When histologically evaluated, the amount of new bone was more pronounced in the GTR-group than in the CT-group, however, no statistical differences in any of the evaluated parameters could be detected between the 2 procedures tested. Frequency and distribution of resorption and ankylosis were similar in the GTR-group and in the CT-group. Within the limits of this study, no differences in terms of the biologic rehabilitation between those recessions treated with ePTFE membranes and those treated with a free connective tissue graft could be found.

Periimplant tissue management: optimal timing for an aesthetic result

When implants are utilized to restore the dentition in an aesthetically prominent region, there are four different time points when the periimplant tissue can be influenced-prior to implant placement, simultaneously with implant placement or during the healing phase of the implant, at second-stage surgery, and during the maintenance phase. There is no single optimal point in time for managing the periimplant tissues; the patients present for treatment at various stages, and each case has to be individually evaluated and an appropriate treatment plan designed. The earlier periimplant tissue management is initiated, the greater are the opportunities for a successful result. The learning objective of this article is to review these options by means of case presentations. The different surgical procedures are explained and their advantages or disadvantages discussed. Four case reports are used to demonstrate the rationale and the clinical procedures. An improvement in the aesthetic harmony was attained in all four cases.

A new technique to combine barrier removal at dehisced implant sites with a plastic periodontal procedure

Three case reports are used to describe a new surgical technique that permits the combination of barrier removal and an apically repositioning flap procedure at implant exposure surgery of previously dehisced or fenestrated implant sites. The flap procedure allows the creation of an adequate zone of keratinized mucosa. In contrast to existing techniques, this method eliminates bone denudation on the interproximal and oral aspect by means of a split-thickness flap surgery. Advantages of this procedure are optimal protection of the bone and reduction of postsurgical discomfort by minimizing the possibility of infection and resorption processes on the bone surface. Furthermore, flap management and fixation are facilitated. Although the necessity of keratinized mucosa around implants is controversial, its presence is favorable in cases where esthetics is important.

Catalase inhibition with 3-amino-1,2,4-triazole does not abolish infarct size reduction in heat-shocked rats

BACKGROUND

Recent studies have shown that improved myocardial salvage after heat-shock pretreatment correlates with the amount of induced cardiac heat-shock protein (HSP)72. However, heat shock also induces myocardial catalase activity, potentially reducing free radical-mediated ischemic injury. The aim of the present study was to determine whether catalase inhibition with 3-amino-1,2,4-triazole (3-AT) abolishes the reduction of infarct size conferred by heat-shock treatment in rats.

METHODS AND RESULTS

Myocardial catalase activity was measured in both heat-shocked and control rats 60 minutes after either 3-AT (1000 mg/kg IV) or saline infusion. In separate experiments, heat-shocked and control rats were treated with 3-AT or saline 60 minutes before being subjected to 35 minutes of left coronary artery occlusion and 120 minutes of reperfusion. Infarct size was determined by dual perfusion with triphenyltetrazolium chloride and phthalocyanine blue dye. Heat-shock treatment significantly increased myocardial catalase compared with control animals (180.5 +/- 4.8, n = 6, versus 86.2 +/- 14.7, n = 5, units/g wet wt; P < .05). Treatment with 3-AT significantly reduced myocardial catalase activity in both heat-shocked and control animals (29.6 +/- 5.7, n = 5, and 36.4 +/- 15.3, n = 6, respectively). Heat-shock treatment significantly reduced infarct size in rats that were both treated and untreated with 3-AT compared with respective control groups (22.5 +/- 3.7%, n = 26, 28.2 +/- 4.0%, n = 22, 52.0 +/- 3.0%, n = 23, and 48.6 +/- 3.2%, n = 26, respectively; P < .0001 for both heat-shocked groups versus both control groups; infarct mass/risk area mass x 100).

CONCLUSIONS

Catalase inhibition with 3-AT does not abolish the reduction of infarct size in heat-shocked rats.

Characterization of the relative thrombogenicity of atherosclerotic plaque components: implications for consequences of plaque rupture

OBJECTIVES

The purpose of this study was to determine whether different components of human atherosclerotic plaques exposed to flowing blood resulted in different degrees of thrombus formation.

BACKGROUND

It is likely that the nature of the substrate exposed after spontaneous or angioplasty-induced plaque rupture is one factor determining whether an unstable plaque proceeds rapidly to an occlusive thrombus or persists as a nonocclusive mural thrombus. Although observational data show that plaque rupture is a potent stimulus for thrombosis, and exposed collagen is suggested to have a predominant role in thrombosis, the relative thrombogenicity of different components of human atherosclerotic plaques is not well established.

METHODS

We investigated thrombus formation on foam cell-rich matrix (obtained from fatty streaks), collagen-rich matrix (from sclerotic plaques), collagen-poor matrix without cholesterol crystals (from fibrolipid plaques), atheromatous core with abundant cholesterol crystals (from atheromatous plaques) and segments of normal intima derived from human aortas at necropsy. Specimens were mounted in a tubular chamber placed within an ex vivo extracorporeal perfusion system and exposed to heparinized porcine blood (mean [+/- SEM] activated partial thromboplastin time ratio 1.5 +/- 0.04) for 5 min under high shear rate conditions (1,690 s-1). Thrombus was quantitated by measurement of indium-labeled platelets and morphometric analysis. Under similar conditions, substrates were perfused with heparinized human blood (2 IU/ml) in an in vitro system, and thrombus formation was similarly evaluated.

RESULTS

Thrombus formation on atheromatous core was up to sixfold greater than that on other substrates, including collagen-rich matrix (p = 0.0001) in both heterologous and homologous systems. Although the atheromatous core had a more irregular exposed surface and thrombus formation tended to increase with increasing roughness, the atheromatous core remained the most thrombogenic substrate when the substrates were normalized by the degree of irregularity as defined by the roughness index (p = 0.002).

CONCLUSIONS

The atheromatous core is the most thrombogenic component of human atherosclerotic plaques. Therefore, plaques with a large atheromatous core content are at high risk of leading to acute coronary syndromes after spontaneous or mechanically induced rupture because of the increased thrombogenicity of their content.

Platelet deposition induced by severely damaged vessel wall is inhibited by a boroarginine synthetic peptide with antithrombin activity

Thrombin plays a key role in platelet activation and thrombosis. Specific inhibition of thrombin appears to be one of the best approaches to prevent thrombus formation. We have studied the effects of a synthetic alpha-aminoboronic acid derivative- [Ac, (D) Phe-Pro-Boro-Arg-Hydrochloric acid] - on platelet deposition on severely damaged arterial wall. Platelet deposition was evaluated under well characterized rheological conditions in an original perfusion chamber and detected by autologous 111In-labeled platelets. The study was performed "in vivo" in a porcine model of arterial thrombosis triggered by severely damaged vessel wall at blood flow conditions mimicking mild stenosis (1690 s-1) and patent (212 s-1) vessels. In addition, ex-vivo platelet aggregation activity was evaluated by whole blood impedance aggregometry using collagen, ADP and thrombin as agonists. The synthetic alpha-aminoboronic peptide was intravenously administered as a bolus followed by continuous infusion. Ex vivo thrombin-induced whole blood platelet aggregation was totally abolished, while ADP- and Collagen-induced whole blood platelet aggregation was not modified. The effects of the synthetic antithrombin on platelet deposition were evaluated in native blood (non-anticoagulated) conditions and in combination with heparin. Under both experimental conditions, the synthetic peptide significantly inhibited platelet deposition at local flow conditions of both high (1690 s-1) and low (212s-1) shear rates. Our results suggest that specific inhibition of locally generated thrombin might be a good strategy to prevent platelet dependent arterial thrombus formation independently of the local flow shear rate of the area at risk.

Blood interactions with novel polyurethaneurea hydrogels

The influence on blood of polyurethaneurea hydrogels in vitro was investigated based on poly(ethylene oxide). A hydrogel was compared with the regenerated cellulose membrane Cuprophan in terms of complement activation, as determined by measurement of C3a concentration. The hydrogel induced less complement activation and the presence of poly(ethylene oxide) is likely to be beneficial to platelet reactivity. The ability to vary the polymer composition and the solubility of the polymers in organic solvents makes the polyurethaneurea hydrogels strong candidates for composite biomaterials.