Tunable Bragg reflectors on silicon-on-insulator rib waveguides

We present the design, fabrication and characterization of Bragg reflectors on silicon-on-insulator rib waveguides. The fabrication is based on a new double lithographic process, combining electron-beam lithography for the grating and photolithography for the waveguides. This process allows the realization of low loss reflectors, which were fully characterized. The influence of the etching depth and of the waveguide geometry on the reflector performance is considered. We demonstrate a reflectivity larger than 80% over a bandwidth of 0.8 nm with an insertion loss of only 0.5 dB. A thermal tunability of the device is also considered, showing that a shift of the reflected wavelength of 77 pm/K is possible.

[Femtosecond laser ablation and scanning microscopy of the internal retinal limiting membrane: an experimental study]

The investigation was undertaken to study whether femtosecond laser ablation and microscopy might be used in the internal retinal borderline membrane. Ablation of internal limiting membrane preparations removed using or not using indocyanine green was made by a low-energy femtosecond laser. Examination of the preparations by laser and electron microscopy revealed precision laser cuts of the internal retinal borderline membrane. The use of indocyanine green during laser ablation reduced laser irradiation parameters as compared to the dye not being applied. Low-energy femtosecond lasers enable precision contactless ablation of the internal borderline membrane to be carried out without collateral damage to the adjacent tissue. The parameters of laser impulses, particularly low ones used in the ablation of indocyanine green-stained preparations, prove the photosensitizing effect of the dye.

Analysis of the S810L Point Mutation of the Mineralocorticoid Receptor in Patients with Pregnancy‐Induced Hypertension

OBJECTIVE

A missense mutation at codon 810 (Ser --> Leu) of the mineralocorticoid receptor was recently observed in a family with early manifestation of hypertension. Our objective was to determine if this mineralocorticoid receptor alterations is prevalent in patients with pregnancy-induced hypertension.

METHODS

Thirty-eight women with hypertension during pregnancy were tested for the mineralocorticoid receptor gene mutation. DNA was extracted out of blood leucocytes. PCR and automated DNA sequencing were used to analyze exon 6 for the S810L missense mutation. Anamnestical data concerning cardiovascular risk factors and family history were evaluated with a questionnaire. Pregnancy course and outcome were documented in all cases.

RESULTS

In 33 patients with pregnancy-induced hypertension and in five patients with exacerbation of preexisting hypertension in pregnancy no point mutations were found at codon 810 in exon 6.

CONCLUSIONS

Our data suggest that the S810L missense mutation of the mineralocorticoid receptor does not play a major role in the etiology of pregnancy-induced hypertension in a German /Turkish population.

Platelet-dependent coagulation assays for factor VIII efficacy measurement after substitution therapy in patients with haemophilia A

FVIII therapy for haemophilia A is safe and effective, with the problem of individually sufficient efficacy unsettled. Routine one-stage clotting assays and tests employing chromogenic substrates poorly detect individual haemostatic effects of FVIII due to artificial test conditions. In particular, the use of cell-free and diluted plasma samples neglect the crucial role of platelets for thrombin and fibrin formation. To optimize FVIII substitution therapy, we measured in 40 patients with severe to mild haemophilia A before and after FVIII substitution the FVIII activity in cell-free plasma samples using a one-stage clotting assay as well a chromogenic substrate assay and compared the data with those obtained with cell-based coagulation tests, i.e. thrombin generation in platelet-rich plasma (PRP) and thromboelastography (TEG) in samples of citrated whole blood (WB). To determine the maximum ex vivo haemostatic effect we added 1 unit/ml of FVIII to samples of PRP and WB and measured the maximum thrombin generation in the thrombin generation test (TGT) and the maximum clot firmness (MCF) in TEG. After FVIII substitution we observed a nearly linear relation between the individual FVIII activities administered to the patients and the activities measured in the plasma samples. However, data obtained with TGT and TEG revealed a high inter-individual variation and a very poor correlation to the administered FVIII activity. Actually, it could be shown that FVIII substitution yielding in a FVIII plasma activity of about 30% is sufficient to get an ex vivo haemostatic effect of more that 90% as measured by maximum thrombin generation and MCF. FVIII substitution up to a plasma activity of more than 90% did not further enhance the haemostatic effect. Our data clearly demonstrate that the haemostatic effect of FVIII is not only dependent on the activity that is measured in plasma but also depends on the interplay between coagulation and blood cells, in particular with platelets. The use of cell-based coagulation tests such us TGT or TEG may help to optimize FVIII therapy by determining the individual FVIII dosage that produces a maximum haemostatic effect.

Impact of increased cell loss on the repopulation rate during fractionated irradiation in human FaDu squamous cell carcinoma growing in nude mice

PURPOSE

To determine the impact of increased necrotic cell loss on the repopulation rate of clonogenic cells during fractionated irradiation in human FaDu squamous cell carcinoma in nude mice.

MATERIALS AND METHODS

FaDu tumours were transplanted into pre-irradiated subcutaneous tissues. This manoeuvre has previously been shown to result in a clear-cut tumour bed effect, i.e. tumours grow at a slower rate compared with control tumours. This tumour bed effect was caused by an increased necrotic cell loss with a constant cell production rate. After increasing numbers of 3-Gy fractions (time intervals 24 or 48 h), graded top-up doses were given to determine the dose required to control 50% of the tumours (TCD50). All irradiations were given under clamp hypoxia.

RESULTS

With increasing numbers of daily fractions, the top-up TCD50 decreased from 37.9 Gy (95% CI: 31; 45) after single dose irradiation to 14.1 Gy (8; 20) after irradiation with 15 fractions in 15 days. Irradiation with 18 daily 3-Gy fractions controlled more than 50% of the tumours without a top-up dose. After irradiation with six fractions every second day, the top-up TCD50 decreased to 26.9 Gy (22; 32). No further decrease of the TCD50 was observed after 12 and 18 irradiations every second day. Assuming a constant increase of TCD50 with time, the calculated doubling time of the clonogenic tumour cells (Tclon) was 7.8 days (4.4; 11.3). The Tclon calculated for FaDu tumours growing in pre-irradiated tissues was significantly longer (p=0.0004) than the Tclon of 5.1 days (3.7; 6.5) determined under the same assumptions in a previous study for FaDu tumours growing in normal subcutaneous tissues.

CONCLUSIONS

Increased necrotic cell loss by pre-irradiation of the tumour bed resulted in longer clonogen doubling times during fractionated radiotherapy of human FaDu squamous cell carcinoma. This implies that a decreased necrotic cell loss might be the link between reoxygenation and repopulation demonstrated previously in the same tumour model.

Selective inhibition of the epidermal growth factor receptor tyrosine kinase by BIBX1382BS and the improvement of growth delay, but not local control, after fractionated irradiation in human FaDu squamous cell carcinoma in the nude mouse

PURPOSE

To investigate the effect of BIBX1382BS, an inhibitor of the epidermal growth factor receptor tyrosine kinase, on proliferation and clonogenic cell survival of FaDu human squamous cell carcinoma in vitro, and on tumour growth and local tumour control after fractionated irradiation over 6 weeks in nude mice. FaDu human squamous cell carcinoma is epidermal growth factor receptor positive and significant repopulation during fractionated irradiation was demonstrated in previous experiments.

MATERIALS AND METHODS

Receptor status, receptor phosphorylation, cell cycle distribution, cell proliferation and clonogenic cell survival after irradiation were assayed with and without BIBX1382BS (5 microM) in vitro. Tumour volume doubling time, BrdUrd and Ki67 labelling indices and apoptosis were investigated in unirradiated tumours growing in NMRI nude mice treated daily with BIBX1382BS (50 mg kg(-1) body weight orally) or carrier. Tumour growth delay and dose-response curves for local tumour control were determined after irradiation with 30 fractions within 6 weeks.

RESULTS

BIBX1382BS blocked radiation-induced phosphorylation of the epidermal growth factor receptor and reduced the doubling time of FaDu cells growing in vitro by a factor of 4.9 (p=0.008). Radiosensitivity in vitro remained unchanged after incubation with BIBX1382BS for 3 days and decreased moderately after 6 days (p=0.001). BIBX1382BS significantly reduced the volume doubling time of established FaDu tumours in nude mice by factors of 2.6 when given over 15 days (p<0.001) and 3.7 when applied over 6 weeks (p<0.001). When given simultaneously to fractionated irradiation, growth delay was significantly prolonged by an average of 33 days (p=0.003). Local tumour control was not improved by BIBX1382BS. The radiation doses necessary to control 50% of the tumours locally were 63.6 Gy (95% confidence interval 55; 73) for irradiation alone and 67.8 Gy (60; 77) for the combined treatment (p=0.5).

CONCLUSIONS

Despite clear antiproliferative activity in rapidly repopulating FaDu human squamous cell carcinoma and significantly increased tumour growth delay when combined with fractionated irradiation, local tumour control was not improved by BIBX1382BS. The results do not disprove that epidermal growth factor receptor inhibition might enhance the results of radiotherapy. However, the results imply that further preclinical investigations using relevant treatment schedules and appropriate endpoints are necessary to explore the mechanisms of action and efficacy of such combinations.

Differentiation status of human squamous cell carcinoma xenografts does not appear to correlate with the repopulation capacity of clonogenic tumour cells during fractionated irradiation

PURPOSE

To investigate the magnitude and kinetics of repopulation in a moderately well differentiated UT-SCC-14 human squamous cell carcinoma [hSCC] in nude mice. This question is of interest because clinical data indicate a higher repopulation capacity in those SCC that have preserved characteristics of differentiation, which appears to be in contrast to results on FaDu and GL hSCC previously reported from this laboratory.

METHODS AND MATERIALS

UT-SCC-14 tumours were transplanted subcutaneously into the right hind leg of NMRI nu/nu mice. Fractionated radiation treatments were delivered, either under clamped hypoxia at 5.4 Gy/fraction or under ambient conditions (consistent with an OER of 2.7). Tumours were irradiated every day, every 2nd day, or every 3rd day with 6, 12 or 18 fractions. 1, 2 or 3 days after the last fraction, graded top-up-doses under clamped conditions were given for the purpose of estimating the 50% tumour control dose (TCD50). A total of 22 TCD50 assays were performed and analysed using maximum likelihood techniques.

RESULTS

The data demonstrate a slow but significant repopulation of clonogenic cells during fractionated irradiation of UT-SCC-14 hSCC. The results under hypoxic conditions are consistent with a constant repopulation rate, with a clonogenic doubling time (Tclon) of 15.6 days (95% CI: 9.7, 21.4). This contrasts with ambient conditions where Tclon was 68.5 days (95% CI: 124, 161). Both Tclon values are longer than the 6-day volume doubling time of untreated tumours.

CONCLUSIONS

Less pronounced repopulation for irradiation under ambient compared to clamped hypoxic conditions might be explained by preferential survival of hypoxic and therefore non-proliferating clonogenic cells. Taken together with previous studies on poorly differentiated FaDu and moderately well differentiated GL hSCC, the results are consistent with considerable variability in the magnitude and kinetics of repopulation in different experimental squamous cell carcinomas, and with a relationship between reoxygenation and repopulation during fractionated irradiation. The differentiation status of hSCC growing in nude mice does not to appear to correlate with the proliferative capacity of clonogenic tumour cells during treatment. The results do not support the hypothesis gained from clinical data of higher repopulation in well-differentiated tumours.

Backscattering and disorder limits in slow light photonic crystal waveguides

It is known that slow light propagation in disordered photonic crystal channel waveguides leads to backscattering and localization phenomena. The knowledge of the reflection of a slow light mode at a single disorder defect of the periodical structure can help to estimate the backscattering intensity and the localization length. Here, this Bloch-mode reflection is calculated in a simplified slow light waveguide using an eigenmode-expansion approach. We show that by properly engineering the waveguide, backscattering can be significantly reduced while maintaining the same low group velocity. A strong effect of the mode's anticrossing taking place in photonic crystal line-defects is demonstrated on backscattering. The localization length of slow light waveguides is estimated, which provides fundamental limits for the applicability of slow light waveguides.

[Relevance of a single dose of 270 microg/kg recombinant factor VIIa for the treatment of patients with haemophilia and inhibitors - Recommendations from the GTH experts]

Recombinant factor VIIa (rFVIIa; NovoSeven) is, besides other indications, authorised for the treatment of bleeding episodes in patients with hereditary haemophilia A or B and inhibitors. Based on the results of three clinical studies, marketing authorisation was granted for the single dose of 270 microg/kg body weight rFVIIa for the treatment of mild to moderate bleeding episodes in patients with haemophilia A or B with inhibitors in March 2007. Thereupon, an expert group analysed the relevance of this additional treatment option for clinical routine. Compared with the repeated application of 90 microg/kg body weight rFVIIa, quality of life may be improved if the single dose of 270 microg/kg body weight rFVIIa reduces the number of injections. The single dose has a benefit for those patients who require several rFVIIa applications or who do not respond adequately to low doses. Moreover, patients with poor venous access or patients who fear injections or reject them (especially children) may benefit from the single dose. The prescription of 270 microg/kg body weight rFVIIa as a single dose instead of multiple dosing of 90 microg/kg body weight is basically an individual and indication-related decision.

Caudal-like PAL-1 directly activates the bodywall muscle module regulator hlh-1 in C. elegans to initiate the embryonic muscle gene regulatory network

Previous work in C. elegans has shown that posterior embryonic bodywall muscle lineages are regulated through a genetically defined transcriptional cascade that includes PAL-1/Caudal-mediated activation of muscle-specific transcription factors, including HLH-1/MRF and UNC-120/SRF, which together orchestrate specification and differentiation. Using chromatin immunoprecipitation (ChIP) in embryos, we now demonstrate direct binding of PAL-1 in vivo to an hlh-1 enhancer element. Through mutational analysis of the evolutionarily conserved sequences within this enhancer, we identify two cis-acting elements and their associated transacting factors (PAL-1 and HLH-1) that are crucial for the temporal-spatial expression of hlh-1 and proper myogenesis. Our data demonstrate that hlh-1 is indeed a direct target of PAL-1 in the posterior embryonic C. elegans muscle lineages, defining a novel in vivo binding site for this crucial developmental regulator. We find that the same enhancer element is also a target of HLH-1 positive auto regulation, underlying (at least in part) the sustained high levels of CeMyoD in bodywall muscle throughout development. Together, these results provide a molecular framework for the gene regulatory network activating the muscle module during embryogenesis.

p53 and p73 in suppression of Myc-driven lymphomagenesis

Induction of apoptosis by the tumor suppressor p53 is known to protect from Myc-driven lymphomagenesis. The p53 family member p73 is also a proapoptotic protein, which is activated in response to oncogenes like Myc. Here, we have investigated whether p73 provides a similar protection from Myc-driven lymphomas as p53. Confirming previous studies, the inactivation of a single p53 allele (p53+/-) strongly reduced the median survival of Emu-Myc transgenic mice from 103 to 39 days and was invariably associated with a loss of the wild-type p53 allele. In contrast, mutational inactivation of a p73 allele (p73+/-) reduced the median survival by only 12 days. Lymphomas that developed in the p73+/- background showed no loss of heterozygosity (LOH). Furthermore, gene expression profiling of p73+/+, p73+/- and p73-/- lymphomas indicated that p73+/- lymphomas retained p73 transcriptional activity. Subtle gene expression differences between p73+/+ and p73+/- lymphomas, however, suggest a haploinsufficient phenotype on some p73 target genes. This might help to explain why p73+/- animals succumbed to disease slightly earlier than their p73+/+ littermates (log-rank test p<0.0395) and why p73 often shows monoallelic inactivation in human lymphomas. Together these data demonstrate that in Myc-driven lymphomagenesis p73 has weak tumor suppressor activity compared with p53.

Anemia treatment with Q2W darbepoetin alfa in patients with chronic kidney disease naïve to erythropoiesis-stimulating agents

OBJECTIVE

To evaluate the efficacy and safety of darbepoetin alfa dosed every-other-week (Q2W) to treat anemia in subjects with chronic kidney disease (CKD), not receiving dialysis, who were naïve to erythropoiesis-stimulating agent (ESA) therapy.

RESEARCH DESIGN AND METHODS

This was an open-label, multicenter, single-arm study enrolling ESA-naïve CKD subjects with baseline hemoglobin (Hb) < 11.0 g/dL. Q2W darbepoetin alfa treatment was initiated at a dose of 0.75 microg/kg and titrated to achieve and maintain Hb levels at 11.0-13.0 g/dL. Treatment was administered from week 1 to week 19.

MAIN OUTCOME MEASURES

The primary endpoint was the proportion of subjects who achieved Hb > or = 11 g/dL at any study visit, except in week 1. Hb levels, darbepoetin alfa dose, and safety were also assessed.

RESULTS

Of the 128 subjects who received at least one dose of darbepoetin alfa and of the subjects who completed the study, 118 (92%) and 112 (97%), respectively, achieved a Hb > or = 11 g/dL in a median time of 5 weeks. Median darbepoetin alfa dose at week 1 and at the time of achieving a Hb > or = 11 g/dL were 60 and 80 microg, respectively. Darbepoetin alfa was well-tolerated, and short-term adverse events were consistent with those expected in CKD subjects.

CONCLUSIONS

This study demonstrates that de novo Q2W darbepoetin alfa was effective in correcting and maintaining Hb levels in ESA-naïve subjects with CKD who were not receiving dialysis. Study limitations, including lack of a control arm for the study and multiple race information for subjects, must be considered in interpreting the results.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov, NCT00112008.

[How does the German DRG system differentiate and reimburse vitreoretinal surgery in diabetic patients?]

INTRODUCTION

The German DRG system (G-DRG system) is required to assign medical cases with similar costs correctly into a particular group, each case within the group receiving the same amount of reimbursement. At the same time the system should allow all-inclusive reimbursement, not necessarily reflecting the exact costs of each case. These opposite goals and the so far limited calculation basis raise the question of how the G-DRG system actually processes and reimburses empirically collected in-hospital treatment data.

PATIENTS AND METHODS

In 2005, 112 patients were admitted to the University Eye Hospital, University of the Saarland. All patients had diabetic retinopathy and required at least one vitreoretinal procedure. Demographic and clinical data were collected by using the hospital information system and the coding software KODIP. For statistic evaluation, principal diagnoses, ancillary diagnoses and procedures were each reassigned to particular groups. Reimbursement was calculated based on the case data of the year 2005. Also, the case data were reassigned with respect to calculation of reimbursement for the years 2006 and 2007. The results were compared with federal G-DRG calculation data.

RESULTS

Mean age of the patients was 65.8 +/- 11.1 years, length of stay in-hospital was 9.3 +/- 3.2 days. In the 66 patients requiring general anaesthesia the cumulative length of stay in the operation room was 148.4 +/- 39.5 minutes, the cumulative duration of surgery was 86.3 +/- 34.1 minutes. In the 50 patients requiring local anaesthesia the cumulative length of stay in the operation room was 137.8 +/- 51.8 minutes, the cumulative duration of surgery was 81.6 +/- 43.6 minutes. The patients had 1.9 +/- 0.8 principal diagnoses, 14.4 +/- 5.8 ancillary diagnoses and 3.4 +/- 1.6 procedures. Twenty-five of 112 patients (22.3 %) were assigned to DRG C 03Z (1), 82 of 112 patients (73.2 %) were assigned to DRG C 17Z (2). Five patients were assigned to other DRG. Compared with the federal calculation data, our own data for 2005, 2006 and 2007 showed more high primary clinical complexity levels and a longer duration of in-hospital stay. For each of the three years the amount of reimbursement was equal in about two thirds of the own patients. Reimbursement was only differentiated for outliers beyond the trim point of the duration of in-hospital stay.

CONCLUSIONS

The demographic and clinical G-DRG data of the included patients showed substantial cost-effective inhomogeneities. These inhomogeneities were not sufficiently considered for reimbursement based upon Z-DRG. Specialised departments with higher numbers of difficult cases may be discriminated. Wrong incentives may result in the selection of "low-risk cases".